Newly Discovered Flower Makes Fake Pollen to Fool Bees

"I was certain it was something new when I saw it," says Chris Martine of the bush tomato species he discovered in the Australian outback. It's a scrappy, spiny shrub with crinkly purple flowers that thrives on fire. It also uses treachery to survive, disguising its female flowers with fake male parts and even fake pollen.

A botanist and biodiversity scientist at Bucknell University, Martine explains that the new plant "was on the radar of a few local botanists as being an oddball." Martine had been studying related species for a decade, so when his lab analyzed this plant's DNA, he recognized that it was something different. He went to Australia to document the species in person and dubbed it Solanum cowiei after botanist Ian Cowie at the Northern Territory Herbarium, who first introduced him to the plant.

The diverse Solanum genus includes plants ranging from potatoes and tomatoes to eggplant and nightshade. The Australian bush tomatoes that Martine studies grow little fruits that can be edible or quite poisonous, depending on the species.

Martine discovered that compared to its relatives, S. cowiei is especially well adapted to the fires that sometimes sweep through its habitat. The plants live in large groups of clones tied together by underground root systems. In an area that had recently been burned clear, Martine found S. cowiei plants springing up and blooming while other species lagged behind. This means that after a fire, these plants have a competitive edge over all their neighbors in getting to pollinators.

The new species's method of reaching those pollinators is a weird one. S. cowiei grows separate male and female flowers, and like about a dozen of its close relatives, it disguises the female flowers with fake male parts and pollen. Under an electron microscope, the false pollen grains look like brand-new tennis balls. Real pollen grains are closer to old ping-pong balls, with large dents or grooves on their surface—these are the weak spots where a narrow tube may later burst out of the wall of the pollen grain, carrying the plant's sperm to an egg.

Why bother with the ruse? Solanum flowers don't have any attractive fragrance to lure their pollinators, or nectar for insects or birds to drink while they're dusted with pollen. Instead, these plants rely on pollinators that want to eat the pollen itself. Certain foraging bees use pollen to feed their young, Martine says. "So if you want one of these bees to visit your flowers, you have to have to have the visual cue of the anthers," a flower's male parts. "And if you want them to come back to flowers like yours again, you have to give them some reward to take away."

Martine and his collaborators are now studying whether this fake pollen is any better or worse for young bees to eat than the real stuff. "Is there a difference in what they are getting?" he says. "Can they tell?"

The "oddball" bush tomato isn't the only plant Martine finds intriguing. He produces an online video series called "Plants Are Cool, Too!" ("Can an animal make its own food? No! Can an animal feed the whole world? No!" the theme song declares.) Martine started this series after working with kids who were interested in science and realizing that they knew a lot about animals, but not so much about plants. People browsing online are more likely to encounter a cute cat video, after all, than one about cattails. So he started putting together episodes that highlight some of the "coolest" plants, along with the botanists who study them.

The next full episode should be out in January, he says, and it includes an especially cool moment: a new species of mustard plant being discovered. "Our guest expert looked down during shooting and said, 'Hey, wait a minute,'" he says. "I don't know how often new species are discovered while a camera is running, but it can't be very common."

Photo by Kym Brennan.

Christopher T. Martine, David E. Symon, & Elizabeth C. Evans (2013). A new cryptically dioecious species of bush tomato (Solanum) from the Northern Territory, Australia. PhytoKeys DOI: 10.3897/phytokeys.30.6003

The Composer and the Cassowary: An Appreciation of Mistakes

High in a church balcony last weekend, waiting to perform a solo for Palm Sunday and trying not to panic, I thought about cars being hit with hammers. I'm not sure this is the kind of visualization recommended for singers. But sometimes genetics asserts itself.

A college biology professor once told my class that genetic mutation is like whacking a car with a hammer. You will almost never improve your car this way. More often, you'll damage it. If you're lucky the damage will be only superficial: a change in the silent portion of your genome, or maybe a few funny feathers.

The piece my choir was getting ready to sing, Gregorio Allegri's Miserere, has experienced some mutations in its own DNA over the centuries. Allegri composed the piece way back in the early 1600s, and after that it was sung exclusively during Holy Week at the Sistine Chapel. Even though people had to attend a 3 AM service in Rome to hear it, the Miserere became famous. The Vatican, wanting to keep the piece to itself, threatened excommunication for anyone who copied down the score.

As secrets and life forms tend to do, though, the music leaked out. In the late 18th century, a certain precocious teenager with the last name of Mozart spent Holy Week in Rome with his father. After hearing the Miserere at the Sistine Chapel, young Wolfgang sat down and transcribed the whole thing from memory. He returned for a second performance to double-check his work. From there, the score got into the hands of a music historian who published it.

If the music had really been genetic material, Mozart would have been DNA polymerase, a molecular machine that copies DNA. The polymerase molecule grasps a DNA strand and crawls along, letter by letter, building a matching strand as it goes.

Like Mozart, the enzyme is good at what it does. It proofreads. But sometimes it slips up: A single letter of DNA might be swapped for another one. A section of the code might be flipped backward. One or more letters might be inserted or deleted. (Even one letter lost or gained can cause a major change, since the DNA code is read in three-letter words. In English, imagine losing a letter from the sentence "SHE ATE THE RED BUG" and ending up with "SEA TET HER EDB UG." Some words are still there, but the meaning of the sentence is destroyed.)

Even if DNA polymerase is performing well, damage to the genome can come from outside sources such as UV radiation. But a large fraction of your DNA seems to do nothing at all. If a mutation happens here, you won't know the difference. If a slip-up creates a synonymous change in a gene—the code allows for some words to be spelled in multiple ways—you'll also be fine. And if the mutation does something horrible, it will remove you from the gene pool.

Evolution doesn't care much about any of this. It only notices the rare constructive strokes of the hammer, and it only sees them if they happen in the cells that will become your sperm and eggs (called the "germ line"). If you have DNA damage in the skin of your back from too much tanning, you can't pass it on to your children.

Back when Allegri's Miserere was being sung in the Sistine Chapel, the choirs were made up of men and boys. In choirs like mine, women sing the alto and soprano parts. But that's only a superficial mutation; we singers are the flesh of the piece.

The germ line mutation came in the 19th century. Someone who copied the piece apparently made a mistake, shifting a whole repeated section up by a fourth. What started out as a normal soprano solo now rocketed all the way to a high C, a preposterous note that humans are almost never asked to sing.*

Natural selection didn't weed out this mutation. Once the change had happened and been passed to new generations of the musical score, it stayed in place—even after the error was discovered. We continue to sing the mutated piece because, simply, it's awesome this way. Here's a video. You'll know when the boy soprano hits the high C: it's the note you hear through the bones of your spine instead of your ears.

It's not an overstatement to say that what happened to Allegri's music represents the whole history of life on Earth. Every new development has come from a mistake, small or egregious, that was allowed to stick around for one reason or another. Life started as tiny blobs, then whoops—heads! Legs! Oops again—tulips! Uncorrected errors became tree bark, snail shells, lungs, fur, resistance to antibiotics. Inching along mistake by mistake, life forms developed the machinery to make blood, slime, deadly venom, and spider silk.

Some living things have come together so elegantly that they bring an audience to its feet. There are racing cheetahs, swooping owls, orchids that mimic bees. But even the giant, gut-colored flower that stinks like a corpse to attract flies is a success in its family line. The cassowary is a bird that made so many mistakes, it traded the ability to fly for tree-trunk legs and a head with a sail on top. Even the cassowary, though, is doing something right. Errors become the high notes.

Postscript: My choir director turns out to have a son who, at age three, actually took a hammer to the family car while it was in the garage. The car was not improved. 

Images: Top, cassowary from The New Student's Reference Work and Gregorio Allegri, both via Wikimedia Commons. Bottom, cassowary by Peter Nijenhuis via Flickr.

*Plot clarification, in case anybody is worrying about me up there in the loft: this is not the part I sang.

How Rice Plants Kick Out Party Crashers

To really sympathize with rice—and to understand why it's developed tricks for bossing insects around—I need you to imagine you're a plant throwing a party.

Have you got it? Let's say it's a sushi-making party, since, you know, you're a rice plant and you already have one ingredient.

So you're Oryza sativa and you're growing in a field somewhere in Asia, and you're enjoying your party with the other rice plants. But then a notorious moocher shows up: the brown planthopper, Nilaparavata lugens. And it brings a whole crowd of its friends.

Next thing you know, the moochers are stealing all your sushi and eating it. Which is to say, they're causing severe crop damage. Brown planthoppers are one of the world's biggest rice pests. They feed on sap from the stems, carry viruses that infect rice plants, and lay new generations of eggs on the leaves.

Since that kind of behavior can ruin a party, you (the rice plant) want to drive the freeloading insects out. You can't physically remove them, so instead you change the tone of your party to something that's not at all their taste. Let's say you switch off the classical music and crank up some heavy metal.

Really, the rice plant emits a chemical called S-linalool into the air when it senses the familiar chewing. Brown planthoppers don't care for the molecule. But if any of them stick around, they'll be sorry. That's because the loud music simultaneously attracts the rice plant's real friends, who love both heavy metal and laying their eggs inside the eggs of brown planthoppers.

These metal fans are the parasitic wasps Anagrus nilaparvatae. Their larvae grow inside the planthopper eggs where they're laid, consuming the unhatched planthoppers from the inside out. And the same chemical signal that hustles the mooching planthoppers out of the party summons the wasps to punish any that stay behind.

Yonggen Lou at the Zhejiang University in China, along with other researchers, found out what the rice plants were up to by spying on them both in the lab and in the field. They knew already that rice plants emit S-linalool when they're chewed on by planthoppers. In fact, all kinds of plants are known to release certain compounds in apparent self-defense. But to understand the crashed house party one step at a time, the scientists created genetically altered rice plants that couldn't make S-linalool at all.

Starting with regular, non-altered rice plants, the researchers showed that S-linalool (the heavy metal music) was turned on whenever brown planthoppers fed on the plants—or when humans repeatedly stabbed the rice stems with tiny needles, imitating planthoppers in search of sap.

Next the researchers released groups of brown planthoppers into cages holding the rice plants. They saw that females preferred to hang out and lay their eggs on the genetically altered plants that couldn't make S-linalool. This means regular, unaltered plants, which could crank up the music when they wanted to, ended up with fewer pest eggs.

To explore the tastes of the parasitic wasps, researchers didn't let them see the plants or the planthoppers at all. Instead, they put the wasps in tubes and gave them whiffs of chemicals previously released by  rice plants. The wasps followed the smell of regular plants that had been chewed by planthoppers—and released S-linalool—but weren't interested in the smell of genetically altered, non-heavy-metal-playing plants.

When the same genetically altered plants were growing in a field, scientists found more than twice as many female planthoppers on them (along with their eggs) than on the regular, S-linalool-producing plants. And the insects on the altered plants had significantly fewer parasitic wasps attacking them. There were also fewer predatory spiders on those plants. The rice plant, despite being stuck in one place and seeming pretty passive, is dictating in detail who's invited to its party. 

Not all compounds emitted by plants are for deterring pests, though. The researchers also studied a second chemical that comes from the rice plant called (E)-β-caryophyllene. Presumably it's helpful to the plants, because they make it all the time. But brown planthoppers are attracted to it—as are their parasitic wasps. At the sushi party, let's call it the beer.

Yonggen Lou thinks farmers might be able to take advantage of the compounds rice plants naturally emit. For example, they could grow rice around the outside of a field that's genetically engineered to produce only (E)-β-caryophyllene (the beer) but not S-linalool (the loud music). These plants would attract both brown planthoppers and their pests. The rest of the rice plants in the field would be engineered in the opposite way, cranking up the heavy metal without providing any beer. Since pests would gather at the edges of the field, where the more attractive molecules were in the air, farmers could reduce their pesticide use and protect their crop. They're the ones, after all, who would really like to be in charge of the guest list.

Xiao Y, Wang Q, Erb M, Turlings TC, Ge L, Hu L, Li J, Han X, Zhang T, Lu J, Zhang G, Lou Y, & Penuelas J (2012). Specific herbivore-induced volatiles defend plants and determine insect community composition in the field. Ecology letters, 15 (10), 1130-9 PMID: 22804824

Image: Brown planthoppers by IRRI Images (Flickr)

Rare Blooms

John pauses with his cursor over a photo of a dark yellow flower. He seems to be debating whether to say something. "I call this one the penis orchid," he admits.

I see it. The Coryanthes bears a bulbous, upright projection, behind which is a bucket-shaped area filled with fluid. Male euglossine bees tumble into the bucket while trying to collect the orchid's fragrance, which they use like a cologne to make themselves more attractive to females. As a male bee repeatedly falls into and crawls back out of these buckets, he unwittingly pollinates the flowers.

It's a great story, but the flower's endowment might be distracting to the middle- and high-schoolers who read the magazine I edit. "Yeah," I tell him, "my photo editor will never let that fly."

I'm visiting my friend John Osterhagen to research an article for kids about orchids. John works for an insurance company by day, but returns home to an apartment bursting with orchid plants. There are eighty or so, living in his bedroom on rows of shelves and windowsills, under special lamps or misting devices. John's cat, Keiko, likes to chew the leaves of just one plant, so he keeps it tucked in his farthest corner.

Flowers aren't John's only self-admittedly strange hobby. He loves early music, origami, and coloring with Crayolas. But none of his other hobbies lives and breathes in his home with him. "People say in the orchid world that you 'get the bug,'" he says. A few fussy but handsome potted plants become shelves full of exotic hybrids and a membership to the Orchid Society. "It's as if the orchids themselves are manipulating you."

John also has the bug for orchid taxonomy, which is always changing as genetic studies revise the family trees guessed at by past centuries' naturalists. He rattles off genus names: Paphiopedilum, Phragmipedium, Bulbophyllum. Sometimes a genus becomes empty and abandoned as taxonomists shift all its species into different groups. John keeps up on the research and edits Wikipedia pages where he can.

The magazine story I'm working on is about deception. Orchids thrive on lying. Some grow petals that look precisely like the back of a female bee or beetle or wasp; a male of the targeted species will try his hardest to mate with the unresponsive flower part while the orchid quietly glues its pollen onto his head. Other species trap their pollinators in well-like petals that can only be exited through a tunnel rigged with pollen. There are orchids that mimic other flowers to attract the pollinators that drink their nectar. (Most orchids don't make nectar, the usual lure for insects, at all.) Those that seek to attract carrion flies mimic rotting meat, emitting a stink from masses of gut-colored petals decorated with maggoty white streaks.

John shows me examples on his computer and on his shelves while Keiko paces around our ankles. A petite epiphytic orchid—a species that lives on trees with its roots dangling into the air—has bloomed just in time for me to see it. He points into the innards of another flower, where I can barely make out the trap door flanked with pollen blobs.

And he points out several species that bear a speckled pattern around their centers, as if a breeze has generously dusted them with their own pollen. In reality, the pollen is waiting elsewhere in a large mass to be attached to a pollinator. John has a strong suspicion that the speckles are another kind of deception, meant to attract insects that eat pollen. "I don't know whether it's been studied academically," he says.

The flowers bloom infrequently and on their own schedules, most often around December or January. Even after putting so much effort into dressing up for a pollinator, they seem not to care whether they get pollinated at all. John says he sometimes gets up in the morning to find that an orchid has tossed a new, perfectly formed blossom to the ground overnight.

The whole family of Orchidaceae, in fact, can appear bent on self-destruction. They grow slowly, sometimes taking years to reach maturity. They're "insanely specialized to their pollinators," many wagering all their future generations on a visit from a single species. If pollinated, they produce seeds that are nearly microscopic. And those seeds can't sprout unless they happen to cross paths with a fungus that will enter into a symbiotic relationship and provide the nutrients the orchid needs. "It seems like the odds are stacked against them," John says.

Yet orchids are some of the most successful plants in the world. There are around 25,000 species, living on every continent except Antarctica and in nearly every kind of climate. They're either the largest or second-largest flowering plant family that exists, depending who does the counting.

The secret to their world dominance may be genetic. During the orchid's evolution, master genes that control the organization of the flower were duplicated. This gave the plant a huge amount of freedom to mutate. New flower shapes emerged to fill thousands, then tens of thousands, of ecological niches.

John doesn't breed his plants. With their expected pollinators never showing up, and John declining to pollinate them by hand, he says they're "the world's most sexually frustrated orchids."

But he does see plenty of mutants. The orchid tendency to create genetic monsters manifests even in his apartment. John shows me a plant that grows flowers with four parts instead of six, and another that has piles of unnecessary petals, "like a Frankenstein flower." He has a plant that can't keep its flowers' lips (the modified petals at the front and center) straight from its other petals. After the mottled fuchsia flowers open, the lips try to turn into petals while the petals start to curl like lips. In a photo, another flower grows an extra petal straight from its center, like an arm coming out of its face.

Orchid growers keep track of individual plants with an elaborate naming system that traces each plant's family history. Thanks to the finickiness of orchid growth, many of these species can't be cloned like other plants can. So their incarnations on John's shelves are one of a kind.

Whether they grow flawless blossoms or freaks, "that particular plant is unique in the whole world," he says. "Like a human."

All images by John Osterhagen. Top to bottom: An orchidarium; Paphiopedilum venustum (a Himalayan species species with a pattern that, John notes, looks like a brain); Jumellea comorense (native to the Comoros Islands in the Indian Ocean); and Dendrobium Negro (a hybrid of Southeast Asian Denbrobium species).

Baby Corn Plants Recruit Helpful Bacteria Posse

When you're a newly sprouted corn seedling, all alone in the dirt, you need any advantage you can get. After all, you can't pick up your roots and travel to find resources or avoid pests. That's why corn plants emit toxic chemicals that keep away hungry insects aboveground and harmful microbes below. But to at least one kind of bacteria, this poison is more of a beacon. They follow the toxic trail back to the corn plant, set up camp in its roots, and help the vulnerable seedling grow.

A plant's roots are the center of a miniature ecosystem called the rhizosphere. Local bacteria feed on sugars and proteins that trickle out of the roots, like antelopes at a watering hole. Symbiotic fungi enmesh themselves in the plant's roots. Helpless as it may appear, the plant can even release chemicals that encourage certain microbes to live there and discourage others, or prevent competing plant species from growing nearby.

Researchers in the United Kingdom studied one of the toxic chemicals released by the roots of corn plants. The compound is a benzoxazinoid, mercifully abbreviated as BX. Seedlings of corn and other grasses secrete BX molecules to protect themselves from pests and harmful microbes.

But the team, led by Andrew Neal at Rothamsted Research, suspected that certain bacteria weren't bothered by the toxin at all. Neal says this was a bit of a "leap of faith." Many bacteria that are used to clean pollutants from soil are closely related to bacteria that colonize plant roots. And some of the toxins that plant roots produce are similar to these pollutants. So the team asked whether Pseudomonas putida--"one of the best root colonizers we know of," Neal says--might be resistant to plant toxins.

The researchers first took both the plants and bacteria out of the soil to see what was going on. They found that corn seedlings produce the most poison at one week old, protecting themselves at their most vulnerable stage of growth. Over the next couple of weeks, production drops off.

Testing P. putida bacteria, they saw that the concentration of BX molecules around a seedling's roots didn't hurt the bacteria at all. But another common soil bacterium had serious trouble growing, even at a much lower concentration of the toxin. The chemical also broke down more quickly in the presence of P. putida, suggesting that the bacteria might not only tolerate the poison, but eat it.

Next Neal and his coauthors turned to the genes of P. putida to see which ones are most active when the toxic chemical is around. A few dozen genes popped up. Some of these had to do with "chemotaxis," a trick in which bacteria use their wiggly arms to travel toward a high concentration of a chemical they like. Were P. putida bacteria actively seeking out the toxin and the corn roots that released it?

Further experiments showed that the bacteria do, in fact, travel toward areas with more BX molecules. And in the soil, corn seedlings making the toxin attract more P. putida to their roots. (Genetic mutants that can't make BX molecules attract fewer bacteria.) The effect fades by the time the plant is three weeks old.

This is the first time scientists have seen an otherwise toxic root chemical attracting helpful bacteria. A corn plant that has successfully recruited P. putida has a leg up--or a root up--in its development. These bacteria and other friendly microbes keep harmful bacteria away by crowding them out and producing antibiotics against them. They also help the plant reach nutrients such as iron and phosphorous in the soil. The bacteria, too, have an advantage over other microorganisms in the area because they can tolerate the plant's toxin and may even eat it.

Neal says that through breeding, some crops have lost their ability to generate this chemical. "Modern varieties of cereals such as corn, wheat, barley, etc., now produce widely varying amounts of the benzoxazinones we studied," he writes. "Some produce quite a lot, others produce none." Neal hopes this research has shown why BX production is a helpful trait for plants to have.

Today's breeders, better informed about what goes on beneath the soil than their predecessors, may want to create new crop varieties that can once again make their own toxins. Plants that generate BX molecules can inhibit pests and diseases--and call friendly bacteria to their aid. We might be able to use fewer pesticides and fertilizers if we let our crops' bacterial helpers help us, too.

Neal, A., Ahmad, S., Gordon-Weeks, R., & Ton, J. (2012). Benzoxazinoids in Root Exudates of Maize Attract Pseudomonas putida to the Rhizosphere PLoS ONE, 7 (4) DOI: 10.1371/journal.pone.0035498


Image: Noël Zia Lee/Flickr

Dinosaur Age Not Dramatic Enough? Add Fire

As if a world dominated by hungry, house-sized lizards weren't sufficiently exciting, scientists have added another set piece to our image of the Cretaceous: raging wildfires.

The Cretaceous period, which ended about 65 million years ago with the extinction of the dinosaurs, was hot. That's thanks to volcanos that pumped carbon dioxide into the atmosphere and created a greenhouse effect. Researchers from London and Chicago now say it was also a "high-fire" world. Frequent blazes may have kept animals on the run, created some of the fossil beds we study today, and helped determine which plant species survived into the next era.

Led by graduate student Sarah Brown from the Royal Holloway University of London, the researchers tracked the appearance of charcoal in ancient sediments. Like a set of sooty footprints right through the fossil record, the charcoal evidence showed when and where fires had occurred.

The team saw that wildfires had increased during the Cretaceous period. These fires were probably sparked by lightning, and their flames were fanned by the high concentration of oxygen in the ancient atmosphere. Today, oxygen makes up about 21% of our air. But during the Cretaceous, it may have risen as high as 25% or more.

This high oxygen content, the authors say, would have allowed plants to burn without being bone dry. A spark in a green forest, instead of dying out as it would today, might become a full-blown fire.

Brown and her coauthors did not find any evidence that these fires contributed to killing off the dinosaurs. But they note that after a fire burns through a piece land, erosion is likely. There may be rapid flooding or mudslides. In the Cretaceous, these events might have trapped and killed dinosaurs and other animal life--and helped preserve their bones.

The authors point to certain fossil beds that lie in floodplains and contain charcoal, as well as plant and animal remains. These could be sites where wildfires triggered flooding, conveniently sweeping lots of informative fossils into one place for future scientists to find.

Charred plant remains in these fossil beds provide another clue about the effect of fire. As the Cretaceous went on, the types of plants being fossilized gradually changed. Flowering plants, called angiosperms, became more and more common. Gymnosperms--the more ancient, flowerless species such as cone-bearing trees, cycads, and ginkgos--faded into the background.

A charred flower fossil from the Late Cretaceous.

Frequent fires may have given an added edge to the angiosperms. The new types of plumbing these plants had invented let them grow faster and more efficiently. Rather than trees, the flowering plants growing during the Cretaceous seem to have been weedy and shrubby types. After a fire, they could regrow faster than the gymnosperms. And their new growth provided fresh fuel for wildfires, creating a cycle that encouraged the growth of flowering plants and left older models in the dust.

Though fire didn't do in the dinosaurs, then, it may have helped set the stage for the dominant plants of the modern age. (As if we needed any more drama.)

Brown, S., Scott, A., Glasspool, I., & Collinson, M. (2012). Cretaceous wildfires and their impact on the Earth system Cretaceous Research DOI: 10.1016/j.cretres.2012.02.008


Images: Gorgosaurus from Nobu Tamura/Wikimedia Commons; flower fossil from Brown et al.

How Stress Makes Oranges Better for You

Though Sicily may seem like a relaxing oasis, it's really a stressful climate where rogue elements can turn you bloody--whether you have a run-in with the mafia, or you're an orange. New research shows why the Italian blood orange prefers this hostile environment to your backyard. With a little coercion, though, we might someday convince this extra-healthy fruit to move abroad.

A variety of the sweet orange Citrus sinensis, the blood orange has eerie red flesh and is grown most successfully around Sicily. To develop their trademark color, the oranges need to ripen in a climate where the nights are much colder than the days. They're cultivated in a few other places outside of Italy, and their color can be enhanced by storing them in the cold after picking them. But in general, the blood orange is an inflexible character.

The blood orange's pickiness makes it hard to mass produce and get onto grocery store shelves. A team of researchers from the United Kingdom, Italy, and China (where another variety of blood orange grows) set out to find what makes the orange so finicky.

Pigments called anthocyanins give the fruit its gory look. These same pigments are responsible for the deep purplish hues of blueberries, eggplant peels, and Japanese maples. Combing through the blood orange's DNA, the researchers found a gene they named Ruby that turns on the fruit's anthocyanin machinery.

When Ruby is activated, the plant makes anthocyanin and the orange turns red. To demonstrate this, the researchers snuck the Ruby gene into a tobacco plant. Tobacco leaves normally make anthocyanin only in small amounts. But with Ruby added to their genes, tobacco plants cranked up the pigment's production and sprouted reddish leaves.

If Ruby is the foreman who hits the ON button at the anthocyanin factory, he apparently needs a cold snap to get him out of bed--because without cold nighttime temperatures, blood oranges don't turn bloody. The researchers discovered that the element waking Ruby up is a kind of rogue gene called a transposon.

Also called "jumping genes," transposons are chunks of DNA that can hop around a genome and insert themselves wherever they like. At some point in the blood orange's evolution, a tranposon stuck itself right in front of Ruby and became the on-switch for the on-switch.

Ordinarily, the plant suppresses the transposon. It's not a good idea, after all, to let wandering genes start bossing around the rest of your DNA. But transposons often get turned on when plants are stressed. Scientists think this may be a desperate trick plants evolved to use when times are tough: The normal order of business isn't working, so plants set their rogue genes free to see if they have any useful innovations. When blood orange trees are stressed by cold temperatures, they release their hold on the transposon in front of Ruby. The transposon wakes up the factory foreman, and you know the rest.

Now that we've found the secret to making blood oranges bloody, senior author Cathie Martin says genetic engineers could create a new variety that doesn't need the cold at all. Scientists could tweak the orange's genome so that Ruby is active all the time, keeping the pigment factory going in any temperature.

Imagining a job for a task force of tree psychologists, I asked Martin if we could grow unmodified blood orange trees in warm climates and just stress them out some other way. But she said that probably wouldn't work. You also can't create a blood orange by chilling regular "blonde" oranges or orange trees--this particular team of rogue gene and factory foreman is specific to this variety of Citrus sinensis.

Of course, you could always just stick to the fruits that grow easily in your climate. But Martin says blood oranges are even better for us than regular oranges. "There are many examples of...dietary anthocyanins having a beneficial effect on health," she says, "especially for cardiovascular disease and obesity." In mice, blood orange juice (but not regular orange juice) limits weight gain and prevents obesity.

If these pigments are as healthful as they seem--and especially if climate change is going to make the tree's home turf less comfortable--maybe it's worth pursuing a way to get the blood orange out of Sicily.



Butelli, E., Licciardello, C., Zhang, Y., Liu, J., Mackay, S., Bailey, P., Reforgiato-Recupero, G., & Martin, C. (2012). Retrotransposons Control Fruit-Specific, Cold-Dependent Accumulation of Anthocyanins in Blood Oranges THE PLANT CELL ONLINE DOI: 10.1105/tpc.111.095232


Image: ccharmon/Flickr

Seeds from 30,000-Year-Old Squirrel Cache Flower Again

Confession: As a nerdlet of nine or ten, I decided to help flowers get fertilized. I loved seeing the glossy seeds hidden inside the fat green ovaries of dead flowers when I split them open with my thumbnail. I must have watched one of those nature specials where the scientists climb up to the top of the Alps and dust pollen onto endangered flowers with a paintbrush, because I started going around roadside fields with cotton balls and gathering pollen. Partway through my project I realized that these particular plants were doing fine without human intervention, and abandoned them.

Now, a group of Russian scientists has given some help to plants that were, unlike my backyard buttercups, definitely not going anywhere on their own. The seeds and fruits of Silene stenophylla were buried 12 stories deep in the Siberian permafrost. They'd been cached there by a ground squirrel some 30,000 years ago. After digging up these long-frozen specimens, a team led by Svetlana Yashina managed to resurrect the ancient organism. They grew healthy plants that flowered and produced their own new, fertile seeds.

When the team excavated this ground squirrel's hoard, they could tell from the ice structures around it that the spot hadn't been touched--or thawed--since it was first interred 30 millennia ago. Though the industrious squirrel had stored a variety of seeds and fruits, previous studies had shown that the seeds of S. stenophylla had a little more liveliness left in them than the others.

From unripe fruits of S. stenophylla, the researchers extracted placental tissue. (Yes, flowering plants have placentas; it's the place where each seed attaches to the ovary. This was news to me too.) They grew this tissue on its own, coaxing it to develop into actual plant shoots. These shoots were fed and grown up into real, potted, flowering plants.

Alongside the ancient and reconstituted plants, the researchers also grew modern plants of the same species. The ancient plants produced up to twice as many flower buds, as if excited to be alive again.

Once the plants had become flowering adults, there were notable differences between the ancient and modern versions. The ancient plants' flower petals, for instance, had a narrower and more shallowly bisected shape. (You can see one of the modern flowers below, and an ancient flower at the top of this page.) The plant was like a snapshot from an earlier stage of its evolution.

Not only did the plants grow and flower--thirty-six of them!--but they were fertile. Scientists demonstrated this by artificially pollinating the plants with each other's pollen (like me with my cotton balls, sort of). Eight or nine weeks later, the plants produced seeds. When scientists gathered these seeds for germination, 100% of them successfully sprouted into new plants. As adults, they grew the same unusual, ancient flower petals that their parents had.

No one has brought a plant this ancient back to life before. The oldest viable seeds ever found are from the first century BC. Yashina writes that the rapid, deep, and permanent freezing of this squirrel's pantry effectively preserved the plant tissues inside. A similar strategy is employed today at the Svalbard Global Seed Vault in Norway, where samples of seeds from around the world are held in an under-ice bunker. If the world's other seed banks are someday destroyed or abandoned, the Svalbard stock can be used to reestablish our crops.

As for seeds that have been unintentionally frozen, there are countless more under the world's icy regions. Permafrost covers a fifth of the planet's surface. If scientists can find other viable plant tissues preserved beneath it, they may discover more species that, like S. stenophylla, have changed since they were frozen--or they could reanimate plants that are now completely extinct.

There's another potential reanimation to consider. Under the permafrost is a rich community of microorganisms, frozen and preserved like the fruits of S. stenophylla. But unlike the flowering plant, which required plenty of manipulation to bring back to life, these organisms are built to last. David Gilichinsky, the senior scientist on this study, has resurrected permafrost bacteria that were frozen for millions of years.

"They are very tough little guys, especially if they are capable of forming spores," McGill microbiologist Lyle Whyte told me. Whyte was not involved in the plant regeneration study, but researches microbes in the Arctic permafrost. He adds that bacteria in, say, million-year-old permafrost may not be quite that old themselves--there's evidence that these frozen communities actually grow and reproduce very slowly while trapped under the ice.

As climate change begins to thaw the permafrost, will some of these frozen microorganisms be awoken and released into the above-ground world? Whether they've been in suspended animation for thousands of years, or quietly reproducing for millions, these microbes would represent strains that modern-day species have never been exposed to. Ancient bacteria--or perhaps viruses or fungi--might discover that the modern world is fertile ground. Humans might discover the Neanderthal flu.

Sadly, David Gilichinsky himself passed away just two days before the publication of his remarkable plant regeneration discovery. "David was at the same time a great expert [on] microorganisms isolated from the cold permafrost and a warm-hearted friend," a colleague wrote on a memorial page. Although Gilichinsky will be greatly missed by his scientific community, he leaves behind him the message that even something unthinkably long gone can be brought back to flowering life.


Svetlana Yashina, Stanislav Gubin, Stanislav Maksimovich, Alexandra Yashina, Edith Gakhova, & David Gilichinsky (2012). Regeneration of whole fertile plants from 30,000-y-old fruit tissue buried in Siberian permafrost. PNAS : 10.1073/pnas.1118386109


Photos: Yashina et al.

Eat Your Grains (They're Controlling Your Genes)

Scientists made the startling assertion this week that RNA from our food can survive digestion, sneak into our cells, and control our genes. Tiny molecular messengers made inside other species--even other kingdoms of species--work just fine in our bodies, latching onto our genetic material and causing system-wide change. Our understanding of diet and nutrition may be in for a shake-up.

A group of researchers in China has been studying microRNAs (abbreviated miRNAs). These stunted nucleotide chains, instead of carrying genetic material themselves, regulate how genes are expressed. MicroRNAs bind to our genes and affect their activity, usually dialing it down. Unlike non-micro DNA or RNA, miRNAs can leave the cell and circulate through the body with the blood.

Looking at a group of healthy Chinese men and women, the researchers identified about 30 miRNAs circulating in their blood that weren't human, or even mammalian, in origin: They came from plants. A structural difference confirmed that the tiny molecules were made in plants, and weren't just animal mimics. Checking the blood of other mammals including mice, horses, and cows, the researchers found more plant miRNAs.

Since a couple of the plant miRNAs that cropped up most often in subjects' bodies are also present in rice, the researchers guessed they were coming from the rice the subjects ate. They used mice to test their theory. The rice miRNA was already present in laboratory mouse chow--explaining its presence in mouse circulatory systems--but there's much more of it in rice. So the scientists fed fresh rice to mice and measured the miRNAs in their systems several hours afterward. Sure enough, higher levels of rice miRNAs appeared throughout the digestive systems of the mice.

The miRNAs seemed to be able to survive both cooking and digestion. Researchers tried leaving them in acid for six hours, simulating the effect of stomach acid, but the miRNAs still didn't break down.

Once intact plant miRNAs left the digestive system and passed into body tissues, were they doing anything? Looking at human cells, the researchers found that the miRNAs from rice latched onto a certain gene that's active in the liver. The gene is responsible for removing LDL ("bad cholesterol") from the circulatory system. When the miRNAs from rice bound to the gene, it was less active. In mice that had eaten rice, the same liver gene was less active--and a few days later, the mice had higher levels of LDL cholesterol in their systems. The liver genes had been dialed down by plant miRNAs, and circulating cholesterol had risen as a result.

The authors think cells in the small intestine take up miRNAs from our digestive tracts, package them into little bubbles called microvesicles, and send them into our circulatory systems. From there, miRNAs find the tissues and cell types they fit best with.

What's incredible is that RNA molecules from an entirely different kingdom of life can affect our genes. The last time we shared a common ancestor with a rice plant, it was single-celled. Almost nothing about us is the same. But their keys still fit in our locks. Plant miRNAs may do a different job in our bodies than in the plants they come from, but we've been evolving with these visitors all along. Our bodies must expect them, and even need them, to enter with our food.

If miRNAs from plants can function in our body, then any and every other food source could be passing us miRNAs that tweak the activity of our genes. "Food-derived miRNAs may serve as a novel essential nutrient," the authors say, as important to our diet as vitamins and minerals. MicroRNAs could be added to foods as fortification. Illnesses could be tied to miRNA deficiencies in our diets. We could take Flintstones chewable miRNAs to stay healthy.

MicroRNAs seem nearly indestructible--they apparently handle being cooked and digested with no problem. But it's possible that our treatment of certain foods destroys their miRNAs. When we eat highly processed foods, are we depriving our bodies of nutrients we never knew existed? And as genetically modified crops become more ubiquitous, we'll want to consider whether we're modifying those crops' miRNAs as well, and how those changes might help or harm us. Staple crops such as rice and corn aren't just foods on our plates; they're also old acquaintances that share responsibility for regulating our genes. Whatever we do to our food, it'll be best if we can still recognize each other.


Zhang, L., Hou, D., Chen, X., Li, D., Zhu, L., Zhang, Y., Li, J., Bian, Z., Liang, X., Cai, X., Yin, Y., Wang, C., Zhang, T., Zhu, D., Zhang, D., Xu, J., Chen, Q., Ba, Y., Liu, J., Wang, Q., Chen, J., Wang, J., Wang, M., Zhang, Q., Zhang, J., Zen, K., & Zhang, C. (2011). Exogenous plant MIR168a specifically targets mammalian LDLRAP1: evidence of cross-kingdom regulation by microRNA Cell Research DOI: 10.1038/cr.2011.158

Non-Aging Plant Gets Better Every Century

Clinging to rock piles high in the Pyrenees, the plant Borderea pyrenaica has a modest lifestyle: It grows a new shoot every summer, flowers and fruits, then sheds its aboveground growth to survive the winter as a tuber. What's remarkable is how long this life lasts for. Individual plants have been known to live 300 years or more. Scientists headed up into the mountains to find out whether these plants, in all their years of living, ever actually get old.

"Senescence" is what we usually call aging--getting weaker and closer to death as we get on in years. To us humans, it seems like a fact of life. But some other animals are thought to be "negligibly senescent." Certain fish, turtles, and other sea creatures seem to be perfectly healthy and fertile at 100 or 200 years old; they're no more likely to die at that age than at any other. Some plants, and especially some trees, may have nearly unlimited lifespans.

Scientists--not to mention cosmetics companies--would love to know exactly why humans are stuck with senescence while organisms like the bristlecone pine just get more fabulous with age. Unfortunately, it's difficult for those of us with limited lifespans to study those without. To squeeze some secrets out of Borderea pyrenaica, scientists from Spain and Sweden studied two populations of the plant over the course of five years.

Because Borderea pyrenaica is left with a scar on its tuber when each year's growth dies back, researchers could count the scars to calculate an individual tuber's age. Each year, they counted and measured the leaves on each plant. They also counted the plants' flowers, fruits and seeds. Since the plants come in male and female versions, the researchers would be able to compare aging in both--would the metabolic effort of making fruits and seeds take a toll on female plants' lifespans? At the end of the study, the researchers dug up all the tubers, dried them and weighed them. (Aesop says: Don't be jealous of negligibly senescent organisms. If old age doesn't kill you, science will!)

The researchers were able to calculate the age of almost 750 plants that were up to 260 years old. They found that tubers grew in size each year, reaching their maximum size after 50 or 100 years (depending on the population). As the tubers grew, the shoots that they put out each year got bigger too. After they reached about 60 years old, the plants didn't seem any more likely to die with the passing years. If anything, survivorship seemed to increase in old age. There was no difference between male and female plants.

As they got bigger, both types of plants put out more flowers, giving them greater potential to contribute to the next generation. This meant that the plants' "reproductive value"--an individual's expected fertility from its current age onward--actually increased over their entire lifespan.

It seems unlikely that we'll one day tap into some biological secret that enables us to live forever. But further research into the plants and animals that don't deteriorate with age might help us solve the mysteries of our own mortality. We may not ever become ageless, but we could learn to age with some of the grace of a lobster, or a mountain tuber.


Garcia, M., Dahlgren, J., & Ehrlén, J. (2011). No evidence of senescence in a 300-year-old mountain herb Journal of Ecology DOI: 10.1111/j.1365-2745.2011.01871.x

Name That Cross Section!

Scroll down through this sequence of pictures. What do you see?

If you said "an artichoke as seen by an MRI machine," you're right! (And this guy would like to talk to you.) 

Andy Ellison is an MRI technician at the Boston University School of Medicine. He first put an orange through the machine one day to make sure it was working correctly. "A problem with the scanner would show itself with most fruits and veggies," he explained to Science. But it turned out that the inside of an orange was pretty cool in its own right. So Ellison started scanning all kids of produce and posting the videos online.

You should definitely go to Ellison's blog, Inside Insides, and watch a few of the videos. Following the scanner through its vegetable odysseys is a little bit like traveling through black hole, or maybe being digested by a squid.

In the meantime, see if you can identify these produce items. Bonus points if you spot any ligament tears.

1.

2.

3.

4.

Answers are in the comments. 

All images from Andy Ellison, Insideinsides.blogspot.com. 

Killer Plant Turns Cute

The children's magazine I edit has a science news feature in every issue, with six or seven quirky stories. It's hard to say exactly how I choose these stories out of all the science news I read each month. But if I had to quantify the process, I'd say I give one point to any item about robots or dinosaurs, two points for cute animals, an extra half-point for anything miniature, and about eleven points for poop. So this story emerged as a clear winner.

In the appealing-sounding "peat swamp forest" of Borneo, a team led by ecologist Ulmar Grafe studied the carnivorous pitcher plant Nepenthes rafflesiana elongata. Compared to the typical variety of its species, the elongata variety is lousy at catching insects for food--seven times worse, in fact. So how does it survive? A clue came when the team discovered tiny bats roosting inside some of the pitchers.

N. rafflesiana elongata has extra-long pitchers that the tiny bats (a subspecies called Hardwicke's woolly bats, with a body just an inch and a half long) can comfortably fit inside. Grafe suspected that the plant and bat had evolved a mutualistic relationship: the bats dozed safely inside the pitchers, and the plants digested the poop their guests left behind. To test this, he glued tiny transmitters onto the bats' backs and tracked which plants they visited. Then he analyzed the nitrogen composition of the pitcher plant leaves.

As Grafe had guessed, the pitchers that housed bats (about a quarter of the elongata pitchers observed during the experiment) had significantly higher nitrogen levels than those that were bat free. The plant hasn't gone totally vegetarian, but supplementing its insect diet with bat droppings seems to have been a successful evolutionary strategy.

The pitchers grow with a tapered shape that bats can wedge their heads down into, so they don't have to cling to the slippery pitcher walls with their feet. The pitchers also have a reduced amount of fluid stored inside; after all, it's hard to convince guests to stay the night when they'll be sleeping with their heads next to a pool of digestive juices. The plant has apparently renovated itself to become a convenient bat hotel. The researchers even found a couple of mother bats roosting with their babies.

No one's ever found a relationship like this before, where a carnivorous plant and a mammal work together. It's almost a heartwarming story--if you can forget about the poop.