published April 14 in the journal Science paint a new picture about apes, ancient Africa and the origins of humans. Many scientists had once hypothesized that the first apes to evolve in Africa more than 20 million years ago ate primarily fruit and lived within the thick, closed canopy of a nearly continent-wide forest ecosystem. Instead, the new research indicates that early apes ate a leafy diet in a more arid ecosystem of varyingly open woodlands with abundant grasses.

The findings by an international team of paleontologists, primate experts and plant scientists — including paleobotanists at the 91̽�� — push the origin of tropical ecosystems dominated by C₄ grasses back by more than 10 million years. In doing so, they link the emergence of C₄ grasses — named for the type of photosynthesis they employ to make food from the sun’s energy — to the emergence of the forerunners to all apes living today. That includes the most abundant ape in history: humans.

Previously, many researchers argued that during the early Miocene, between about 15 and 20 million years ago, equatorial Africa was covered by a semi-continuous forest. Under that hypothesis, more open habitats with C₄ grasses didn’t proliferate until about 8 to 10 million years ago. Yet one study showed some evidence of C₄ grasses in East Africa around 15 million years ago. The research team wanted to understand if that study was an anomaly or a clue to the true diversity of ecosystems at that time.

“The history of grassland ecosystems in Africa prior to 10 million years had remained a mystery, in part because there were so few plant fossils,” said co-author , the Estella B. Leopold Professor of Biology at the UW.

The international collaboration — funded largely by the National Science Foundation — drew together multiple different lines of evidence to try to reconstruct the species that dominated East Africa in the early Miocene. Researchers incorporated analyses of fossil soils, animal fossils, stable isotopes and phytoliths, which are plant silica microfossils.

Strömberg, who is an expert in phytoliths, worked with co-authors Alice Novello, a former 91̽��postdoctoral scientist who is currently working at Aix-Marseille University in France, and of the National Museums of Kenya and the Max Planck Institute of Geoanthropology in Germany to reconstruct what types of plants were present at several sites in East Africa during the early Miocene.

“Phytoliths are particularly informative for revealing the history of grassland ecosystems. They can tell us not just that there were grasses, but which grasses were there and how abundant they were on the landscape,” said Strömberg, who is also curator of paleobotany at the UW’s .

Their data, combined with other lines of evidence, essentially disproved the theory that equatorial Africa in the early Miocene was heavily forested. The findings have important implications for understanding the features and adaptations of early apes.

“Multiple lines of evidence show that C₄ grasses and open habitats were important parts of the early Miocene landscape and that early apes lived in a wide variety of habitats, ranging from closed canopy forests to open habitats like scrublands and wooded grasslands with C₄ grasses,” said co-author , an associate professor of geosciences at Baylor University. “It really changes our understanding of what ecosystems looked like when the modern African plant and animal community was evolving.”

“What we found was thrilling, and very different from what was the accepted story,” said Strömberg. “We used to think tropical, C₄ dominated grasslands only appeared in the last 8 million years or so, depending on the continent. Instead, both phytolith data and isotopic data showed that C₄ dominated grassy environments appeared over 10 million years earlier, in the early Miocene in eastern Africa.”

In addition to its findings about C₄ grassy habitats, the team is also reporting discoveries about a 21-million-year-old fossil ape, Morotopithecus. Anthropologists long thought that our ape ancestors evolved an upright torso in order to pick fruit in forests. With an upright posture, an ape can more easily grab onto different branches with its hands and feet. Morotopithecus definitely had an upright stature. Paleontologists on the team performed careful analyses of the shape of its molars, as well as the chemical composition of its dental enamel, to determine its diet.

“The expectation was: We have this ape with an upright back. It must be living in forests and it must be eating fruit,” said co-author , a professor of anthropology at the University of Michigan. “But as more and more bits of information became available, the first surprising thing we found was that the ape was eating leaves. The second surprise was that it was living in woodlands.”

Together, the evidence showed that Morotopithecus lived in a seasonal woodland with a broken canopy composed of trees and shrubs and open, grassy areas. In addition, the team’s plant and climate reconstruction efforts determined that, for at least part of the year, Morotopithecus had to rely on leaves and other plant material — instead of fruit — for food.

The fact that abundant C₄ grass and woodland ecosystems arose much earlier than once thought also upends another view of human origins: That our bipedalism evolved as a response to the emergence of grassland environments in Africa between 10 and 7 million years ago.

“Now that we’ve shown that such environments were present at least 10 million years before bipedalism evolved, we need to really rethink human origins, too,” said MacLatchy.

In addition to MacLatchy, Strömberg, Kinyanjui and Peppe, other lead researchers on the collaboration behind these discoveries include co-authors , associate professor of anthropology and archaeology at the University of Calgary; , a professor of anthropology at the University of Minnesota; , professor of Earth and environmental sciences at the University of Minnesota; and , an associate professor of anthropology at the University of Michigan. Many members of the team participated through the Research on East African Catarrhine and Hominoid Evolution — or — Project. Strömberg and Novello initially participated through separate funding from the European Union to study the evolution of grasslands in East Africa.

For more information, contact Strömberg at caestrom@uw.edu.

Adapted from press releases by the and .

Botanists at the 91̽��’s have created a much-needed second edition of the “Flora of the Pacific Northwest.” Published by the 91̽��Press, took five years to complete and is the first update on Pacific Northwest vascular plant diversity and distributions since the book was first published in 1973. In the past 45 years, much has changed: The second edition documents the doubling of nonnative species in the Pacific Northwest, the addition of 1,000 taxa — including species, subspecies and varieties — to the region’s flora, and the reclassification or renaming of 40 percent of the taxa in the first edition.

The original “Flora of the Pacific Northwest” became an instant classic for its innovative style providing species descriptions in the identification keys and for its comprehensive illustrations of nearly all treated taxa. Students rely on it as an essential primer, while veteran botanists and natural resource managers use it as the definitive reference for the region’s flora.

“This book enables us to be better stewards, we know what’s here, whether it’s common or rare, or invasive,” said , collection manager for the at the Burke Museum. “It enhances our ability to preserve plant diversity in our region for future generations.”

This completely revised and updated edition captures the advances in vascular plant systematics since the first edition. These advances, together with significant changes in plant nomenclature, the description of taxa new to science from the region, and the recent documentation of new native and nonnative species in the Pacific Northwest, required a thorough revision of this authoritative work.

“Flora of the Pacific Northwest” covers all of Washington, the northern half of Oregon, Idaho north of the Snake River Plain, the mountainous portion of western Montana, and the southern portion of British Columbia. It accounts for wild-growing native and introduced vascular plants falling within those boundaries and includes:

• Treatment of 5,545 taxa, with more than 1,100 taxa added to this edition
• Illustrations for 4,716 taxa, including 1,382 new for this edition
• More than 700 newly documented nonnative taxa in the Pacific Northwest
• Nomenclature changes for more than 40 percent of the taxa included in the first edition

These enhancements make this new edition the most comprehensive reference on Pacific Northwest vascular plants for professional and amateur botanists, ecologists, rare plant biologists, plant taxonomy instructors, land managers, nursery professionals and gardeners.

The 1,100 new taxa consist mainly of existing native and nonnative species newly documented in the region, as well as a number of taxa new to science. Many of the new regional records were collected during the herbarium’s annual forays held throughout the Pacific Northwest.

“With the recent revision of ‘,’ and the soon-to-be-completed ‘Flora of Oregon,’ up to date floristic treatments are now available for the entire West Coast of the U.S.,” said , 91̽��biology professor and curator of the 91̽��Herbarium at the Burke Museum.

The new illustrations are in the style of the 3,000 original illustrations, by illustrators Jeanne R. Janish and John Ramely, found in the 1973 edition of the “Flora.”

Crystal Shin, a scientific illustrator and the primary illustrator for the revision, worked to match the style of the original illustrations so the more than 1,300 new illustrations she created seamlessly fit.

“Before inking, I study the style and techniques that Jeanne used on a similar species,” said Shin. “I like her work very much and my ink drawing style is pretty close to hers.”

Shin started the illustration process with a plant specimen by reviewing the specimen’s characteristics with one of the Burke Museum botanists. Together they determined which parts of the plant to include in the illustration. Shin then used a microscope and magnifying glass to examine the plant’s details, specifically its length of hairs, textures, marks, veins, shapes and more. After studying the plant, she proceeded with the illustration process of pencil sketching and then inking. Project staff then scanned, edited and archived the illustrations for later placement alongside the text.

It took approximately two hours to complete each illustration before being placed on the page in the book.

The newest edition of “Flora of the Pacific Northwest” can be purchased for $75.00 at the University Bookstore, local bookstores, and book retailers across the country and .

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For high-resolution images and interviews, contact burkepr@uw.edu or uwpmktg@uw.edu.

Plant scientists have observed that when levels of carbon dioxide in the atmosphere rise, most plants do something unusual: They thicken their leaves.

And since human activity is raising atmospheric carbon dioxide levels, thick-leafed plants appear to be in our future.

But the consequences of this physiological response go far beyond heftier leaves on many plants. Two 91̽�� scientists have discovered that plants with thicker leaves may exacerbate the effects of climate change because they would be less efficient in sequestering atmospheric carbon, a fact that climate change models to date have not taken into account.

In a published online Oct. 1 by the journal , the researchers report that, when they incorporated this information into global climate models under the high atmospheric carbon dioxide levels expected later this century, the global “” contributed by plants was less productive — leaving about 5.8 extra petagrams, or 6.39 billion tons, of carbon in the atmosphere per year. Those levels are similar to the amount of carbon released into the atmosphere each year due to human-generated fossil fuel emissions — 8 petagrams, or 8.8 billion tons.

“Plants are flexible and respond to different environmental conditions,” said senior author , a 91̽��assistant professor of atmospheric sciences and biology. “But until now, no one had tried to quantify how this type of response to climate change will alter the impact that plants have on our planet.”

In addition to a weakening plant carbon sink, the simulations run by Swann and , a 91̽��doctoral student in biology, indicated that global temperatures could rise an extra 0.3 to 1.4 degrees Celsius beyond what has already been projected to occur by scientists studying climate change.

“If this single trait — leaf thickness — in high carbon dioxide levels has such a significant impact on the course of future climate change, we believe that global climate models should take other aspects of plant physiology and plant behavior into account when trying to forecast what the climate will look like later this century,” said Kovenock, who is lead author on the paper.

Scientists don’t know why plants thicken their leaves when carbon dioxide levels rise in the atmosphere. But the response has been documented across many different types of plant species, such as woody trees; staple crops like wheat, rice and potatoes; and other plants that undergo , the form of photosynthesis that accounts for about 95 percent of photosynthetic activity on Earth.

Leaves can thicken by as much as a third, which changes the ratio of surface area to mass in the leaf and alters plant activities like photosynthesis, gas exchange, evaporative cooling and sugar storage. Plants are crucial modulators of their environment — without them, Earth’s atmosphere wouldn’t contain the oxygen that we breathe — and Kovenock and Swann believed that this critical and predictable leaf-thickening response was an ideal starting point to try to understand how widespread changes to plant physiology will affect Earth’s climate.

“Plant biologists have gathered large amounts of data about the leaf-thickening response to high carbon dioxide levels, including atmospheric carbon dioxide levels that we will see later this century,” said Kovenock. “We decided to incorporate the known physiological effects of leaf thickening into climate models to find out what effect, if any, this would have on a global scale.”

A by researchers in Europe and Australia collected and catalogued data from years of experiments on how plant leaves change in response to different environmental conditions. Kovenock and Swann incorporated the collated data on carbon dioxide responses into Earth-system models that are widely used in modeling the effect of diverse factors on global climate patterns.

The concentration of carbon dioxide in the atmosphere today hovers around 410 parts per million. Within a century, it may rise as high as 900 ppm. The carbon dioxide level that Kovenock and Swann simulated with thickened leaves was just 710 ppm. They also discovered the effects were worse in specific global regions. Parts of Eurasia and the Amazon basin, for example, showed a higher minimum increase in temperature. In these regions, thicker leaves may hamper evaporative cooling by plants or cloud formation, said Kovenock.

Swann and Kovenock hope that this study shows that it is necessary to consider plant responses to climate change in projections of future climate. There are many other changes in plant physiology and behavior under climate change that researchers could model next.

“We now know that even seemingly small alterations in plants such as this can have a global impact on climate, but we need more data on plant responses to simulate how plants will change with high accuracy,” said Swann. “People are not the only organisms that can influence climate.”

The research was funded by the National Science Foundation and the UW.

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For more information, contact Swann at +1 206-616-0486 or aswann@uw.edu.

DOI: 10.1029/2018GB005883

Grant numbers: AGS-1321745, AGS-1553715.

Knowledge of this process at the cellular level is critical for understanding how plants allocate resources and produce the components we care most about — including the grains, tubers, leaves, nuts and fruits that mean so much to humans and animals alike.

In a published Sept. 24 in the journal , an international team of researchers has discovered that the gene FT — the primary driver of the transition to flowering in plants each spring — does something unexpected in plants grown in natural environments, with implications for the artificial growing conditions scientists commonly used in the lab. The team, led by 91̽�� biology professor , showed that FT has a peak of activity every morning leading up to the transition, something that scientists had not previously seen in Arabidopsis, a model plant that is widely studied for understanding the molecular details of the transition to flowering. The morning peak of FT activity causes plants to transition earlier from vegetative growth to flowering.

“Previous research on FT activity in Arabidopsis showed that there is a peak of activity in the evening, not the morning,” said Imaizumi, who is senior author on the paper. “We show definitively that there is a peak of morning activity — and we think we know why this morning peak was not seen previously in the research laboratory.”

Prior research, which saw only an evening peak of FT gene activity, had been conducted on Arabidopsis plants grown indoors under fluorescent light. Imaizumi and his team — which includes researchers in Switzerland, Scotland, South Korea and Japan — grew their plants outside under sunlight.

Imaizumi wanted to do this experiment because conditions at the summer solstice in Seattle, where his lab is located, are similar to the standardized, artificial “long-day” growing conditions for Arabidopsis: 16 hours of light and eight hours of darkness.

“I always wanted to grow plants outdoors in conditions similar to the lab just to make sure that what we’re seeing in lab with Arabidopsis is really what’s happening in nature,” said Imaizumi.

His team grew non-transgenic Arabidopsis plants outdoors for five consecutive summers and compared them to plants grown indoors under artificial long-day conditions. Outdoor plants produced fewer leaves than indoor plants, indicating that the outdoor plants flowered earlier. Both outdoor and indoor plants showed evening peaks of FT gene activity, but outdoor-grown plants also showed a morning peak of FT activity. They concluded that the indoor, artificial growing conditions missed key qualities of natural conditions, throwing off expression of the FT gene and the trait it governs. When active, the FT gene produces a protein that travels from the leaves to the shoot apical meristem — the niche of stem cells in the shoot that produces above-ground growth — and switches the meristem from vegetative growth to floral growth.

To identify the differences between indoor and outdoor growing conditions, Imaizumi’s group focused on light. The fluorescent bulbs commonly used in Arabidopsis research do not emit the same wavelengths of light that sunlight does. Fluorescent bulbs, for example, generate less light from far-red wavelengths. In the outdoor growing plots, the ratio of red-wavelength light to far-red wavelength was about 1-to-1, but for fluorescent bulbs this ratio is higher than 2, which means they emit more red light than far-red. When the researchers added a far-red LED lamp to the indoor growth chambers to mimic outside light, the Arabidopsis plants then showed a morning peak of FT gene activity.

In addition, by modifying the temperatures in the indoor growth chambers to cycle daily from about 16 degrees Celsius to almost 23 C — or from 61 degrees Fahrenheit to about 73 F — the evening FT gene activity was reduced, similar to the outdoor plants.

FT has been studied in other plants, including some crop plants, which also show morning peaks of FT expression. But most commercially important plants are too large or grow too slowly for the controlled-environment studies that are required to determine the cellular and genetic details of plant traits. That is why Arabidopsis, a small, fast-growing weed from the mustard family, is widely used as a substitute model organism.

The team’s findings are an opportunity to revisit the artificial growing conditions, according to Imaizumi.

“Arabidopsis has been studied for decades. Researchers set up their indoor growing conditions the best they could, given equipment, time and funding, and passed those conditions down to scientists they trained,” said Imaizumi. “But we need to change those conditions so that what we find in the lab reflects nature more closely. If we see a change in flowering by making these minor alterations, I imagine that other traits will change as well.”

Critically, their results illuminate a path forward for plant researchers to adopt artificial growth conditions that more accurately reflect natural growing conditions.

“We show that just a few simple modifications are needed to the artificial growing conditions, which researchers are using worldwide, so that lab research on Arabidopsis more and other plants accurately mimics outdoor growing conditions,” said Imaizumi. “This ensures that the discoveries made in the lab will be more comparable to what the biological processes are — at the cellular and molecular level — in other plants of interest in nature.”

Co-lead authors on the paper are former 91̽��postdoctoral researchers Young Hun Song and Akane Kubota. Song is now an assistant professor at Ajou University and Kubota is an assistant professor at the Nara Institute of Science and Technology. Co-authors are Michael Kwon, Nayoung Lee, Ella Taagen, Dianne Laboy Cintrón, and Nhu Nguyen at the UW; Michael Covington with Amaryllis Nucleics; Dae Yeon Hwang at Ajou University; Sarah Hodge and Andrew Millar at the University of Edinburgh; He Huang and Dmitri Nusinow at the Donald Danforth Plant Science Center; Reiko Akiyama with the University of Zurich; and Kentaro Shimizu of both the University of Zurich and Yokohama City University. The research was funded by the U.S. National Institutes of Health, the U.S. National Science Foundation, the Rural Development Administration in South Korea, the Japan Science and Technology Agency, the Japan Society for the Promotion of Science, the Swiss National Science Foundation, UK Biotechnology and Biological Sciences Research Council, and the National Research Foundation of Korea.

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For more information, contact Imaizumi at 206-543-8709 or takato@uw.edu.

DOI: 10.1038/s41477-018-0253-3

Grant numbers: GM079712, IOS-1656076, IOS-1456796, PJ013386, JPMJCR16O3, 17H04785, NRF-2015R1D1A1A01058948, BB/N012348/1, DBI-0922879.

Through photosynthesis, they use sunlight and carbon dioxide to make food, belching out the oxygen that we breathe as a byproduct. This evolutionary innovation is so central to plant identity that nearly all land plants use the same pores — called stomata — to take in carbon dioxide and release oxygen.

Stomata are tiny, microscopic and critical for photosynthesis. Thousands of them dot on the surface of the plants. Understanding how stomata form is critical basic information toward understanding how plants grow and produce the biomass upon which we thrive.

In published May 7 in the journal , a 91̽��-led team describes the delicate cellular symphony that produces tiny, functional stomata. The scientists discovered that a gene in plants known as MUTE orchestrates stomatal development. MUTE directs the activity of other genes that tell cells when to divide and not to divide — much like how a conductor tells musicians when to play and when to stay silent.

“The MUTE gene acts as a master regulator of stomatal development,” said senior author , a 91̽��professor of biology and investigator at the . “MUTE exerts precision control over the proper formation of stomata by initiating a single round of cell division — just one — in the precursor cell that stomata develop from.”

Stomata resemble doughnuts — a circular pore with a hole in the middle for gas to enter or leave the plant. The pore consists of two cells — each known as a guard cell. They can swell or shrink to open or close the pore, which is critical for regulating gas exchange for photosynthesis, as well as moisture levels in tissues.

“If plants cannot make stomata, they are not viable — they cannot ‘breathe,’” said Torii, who also is a professor at Nagoya University in Japan.

Torii and her team investigated which genes governed stomata formation in Arabidopsis thaliana, a small weed that is one of the most widely studied plants on the planet. Past research by Torii’s team and other researchers had indicated that, in Arabidopsis, MUTE plays a central role in the formation of stomata. The MUTE gene encodes instructions for a cellular protein that can control the “on” or “off” state of other plant genes.

The researchers created a strain of Arabidopsis that can artificially produce a lot of the MUTE protein, so they could easily identify which genes the MUTE protein turned on or off. They discovered that many of the activated genes control cell division — a process that is critical for stomatal development.

In Arabidopsis, as in nearly all plants, stomata form from precursor cells known as guard mother cells, or GMCs. To form a working stoma — singular for stomata — a GMC divides once to yield to paired guard cells. Since their data showed that MUTE proteins switched on genes that regulated cell division, Torii and her team wondered if MUTE is the gene that activates this single round of cell division. If so, it would have to be a tightly regulated process. The genetic program would have to switch on cell division in the GMC, and then quickly switch it right back off to ensure that only a single round of division occurs.

Torii’s team showed that one of the genes activated by the MUTE protein to its DNA is CYCD5;1, a gene that causes the GMC to divide. The researchers also found that MUTE proteins turn on two genes called FAMA and FOUR LIPS. This was an important discovery because, while CYCD5;1 turns on cell division of the GMC, FAMA and FOUR LIPS turn off — or repress — the cell division program.

“Our experiments showed that MUTE was turning on both activators of cell division and repressors of cell division, which seemed counterintuitive — why would it do both?” said Torii. “That made us very interested in understanding the temporal regulation of these genes in the GMC and the stomata.”

Through precise experiments, they gathered data on the timing MUTE activation of these cell division activators and repressors. They incorporated this information into a mathematical model, which simulated how MUTE acts to both activate and repress cell division in the GMC. First, MUTE turns on the activator CYCD5;1 — which triggers one round of cell division. Then, FAMA and FOUR LIPS act to prevent further cell division, yielding one functional stomata consisting of two guard cells.

“Like a conductor at the podium, MUTE appears to signal its target genes — each of which has specific, and even opposite, parts to play in the ensuing piece,” said Torii. “The result is a tightly coupled sequence of activation and repression that gives rise to one of the most ancient structures on land plants.”

Co-lead authors on the paper are Soon-Ki Han, a former 91̽��postdoctoral researcher now at Nagoya University, and 91̽��postdoctoral researcher Xingyun Qi. Additional co-authors are Jonathan Dang, Kristen Miller and Eun Deok Kim at the UW; Kei Sugihara and Takashi Miura at Kyushu University; and Takaho Endo at the RIKEN Center for Integrative Medical Sciences. The research was funded by the National Science Foundation, the Gordon and Betty Moore Foundation and the HHMI.

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For more information, contact Torii at 206-221-5701 or ktorii@uw.edu.

Grant numbers: MCB-0855659, GBMF-3035.

A lab-designed hormone could unlock mysteries harbored by plants.

By developing a synthetic version of the plant hormone auxin and an engineered receptor to recognize it, 91̽�� biology professor and her colleagues are poised to uncover plants’ inner workings.

The new work, described in a published online Jan. 22 in , is a “transformative tool to understand plant growth and development,” said Torii, who is also an with the . That understanding may have big agricultural implications, raising the possibility, for instance, of a new way to ripen fruits such as strawberries and tomatoes.

To plants, the hormone is king. Among many other jobs, auxin helps sunflowers track sunlight, roots grow downward and fruits ripen. This wide range of jobs, as well as the fact that every cell in a plant can both produce and detect auxin, makes it tricky to tease apart the hormone’s various roles.

“It’s been a huge mystery as to how such a simple molecule can do so many different things,” said Torii, who is senior author on the paper.

She and her colleagues set out to create a new way to study plants’ responses to auxin by designing a lab-made version of the hormone that can be precisely controlled. Working with , the researchers added a little bump to auxin’s structure — hydrocarbon rings that auxin doesn’t normally contain. The researchers then tweaked plants’ auxin receptor, a protein that sits on the outside of plant cells and detects auxin. They removed a bulky amino acid from the receptor, creating a perfect-sized hole that cradles the lab-made auxin.

That simple switch, called a “bump and hole” strategy, “is really elegant, actually,” said Torii.

Next, the researchers tested whether this matched set — the synthetic auxin and the synthetic receptor — could do the same jobs as the cells’ natural auxin/receptor pair. The intricately designed system worked beautifully, based on results from experiments on roots.

Normally, roots exposed to auxin stop growing down, and instead grow sideways by activating stem cells that break out of the main root. The process, called lateral root development, is comparable to aliens bursting through stomachs, said Torii. After detecting synthetic auxin, Arabidopsis plants genetically engineered to produce the synthetic auxin receptor behaved just like normal — growing the same sideways baubles of root branches.

What’s more, roots that didn’t have the synthetic auxin receptor were essentially “blind” to synthetic auxin, proof that the artificial hormone is detected by only the artificial receptor. Torii and her colleagues call this switch to synthetic auxin “chemical hijacking” — a well-controlled takeover that now will allow researchers to tease apart the tangled web of auxin’s jobs in plants.

With their system up and running, the researchers tested a long-standing question in plant biology. Scientists knew that germinating seedlings use auxin to grow quickly. But the identity of the exact receptor that allows this process to happen wasn’t settled.

The scientific community had a suspect in mind. Torii’s team produced a plant that lacked an auxin receptor called TIR1, and instead possessed a synthetic version. When exposed to artificial auxin, these seedlings began to grow rapidly, behaving exactly as if they had the normal receptor. The results suggest that seed elongation does indeed happen through the TIR1 receptor.

Other fundamental scientific questions can be addressed with this system, Torii said, such as auxin’s role in corn ripening and in opening the stomata, the structures that let plants breathe.

One day, synthetic auxin might even find a place in agriculture. Auxin is currently sprayed on fruits to hasten ripening. But in high concentrations, the hormone can act as a plant-killing herbicide. Fruits engineered to carry the synthetic receptor could be ripened with the synthetic auxin hormone, Torii said, eliminating the need to spray auxin indiscriminately. But, she cautions, much more testing needs to be done before a synthetic hormone system can be used for growing food.

Naoyuki Uchida and Koji Takahashi at Nagoya University are co-lead authors on the paper. Co-authors on the study are Rie Iwasaki, Ryotaro Yamada, Masahiko Yoshimura, Hua Zhang, Mika Nomoto, Yasuomi Tada, Toshinori Kinoshita, Kenichiro Itami and Shinya Hagihara at Nagoya University; Takaho Endo with the ; and Seisuke Kimura at . The research was funded by the Japan Society for the Promotion of Science; the Ministry of Education, Culture, Sports, Science and Technology of Japan; the Japan Science and Technology Agency; the Howard Hughes Medical Institute; and the .

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For more information contact Torii at ktorii@uw.edu.

Adapted from a by the Howard Hughes Medical Institute.

Grant numbers: JP26291057, JP16H01237, JP17H06476, JP16H01462, JP17H03695, JP17KT0017, JP26440140, JP15H05956, JP17H06350, JP16H01472, S1511023, JPMJPR15Q9, JPMJER1302, GBMF3035.

You read that right. Plants have hormones.

Hormones are small signaling molecules that travel between cells and deliver messages to switch on and off specific genes — affecting behavior, environmental responses and growth. Human hormones include testosterone, insulin and the aptly named growth hormone. Plant hormones are an entirely different set of chemical messengers, which modulate activities such as stem growth, leaf and flower production, root patterning and coping with environmental disruption.

These are just the sorts of tasks that plant biologists seek to understand with precision as the pressure increases to feed a growing population amid unchecked climate change. But hormones in plants affect such a wide variety of genes and plant activities that the fine details of hormone responses are — at best — murky.

Researchers at the 91̽�� have developed a novel toolkit based on modified yeast cells to tease out how plant genes and proteins respond to , the most ubiquitous plant hormone. Their system, described in published Sept. 19 in the , allowed them to decode auxin’s basic effects on the diverse family of genes that plants utilize to detect and interpret auxin-driven messages.

“Auxin has different messages in different contexts,” said senior author and 91̽��biology professor . “One cell responds to auxin one way, while its neighbor does the exact opposite — two different responses from the same chemical. What inside these cells is happening to deliver opposite messages?”

As the most widespread plant hormone, auxin affects nearly every aspect of plant biology, including growth, development and stress response. Biologists have long known that auxin acts on stretches of DNA, called promoters, to turn nearby genes on or off. But auxin doesn’t simply turn all nearby genes on or off. With auxin, some genes turn on, others are switched off and even more nuanced responses are possible. Plant proteins mediate these varied responses by binding to auxin and then to promoters. Some proteins decrease gene expression, while others do the opposite.

“There is a large amount of cross-communication between proteins, and plants have a huge number of genes that are targets for auxin,” said Nemhauser. “That makes it incredibly difficult to decipher the basic auxin ‘code’ in plant cells.”

So Nemhauser’s team switched from plant cells to — a single-celled fungus and popular laboratory tool. The researchers engineered yeast cells to express proteins that responded to auxin, so they could measure how auxin modified the on/off state of key plant genes that they also inserted into the cells. In essence, they jury-rigged yeast to respond to auxin. To Nemhauser, this was a simple shift in approach with a potentially huge payoff.

“We changed the perspective of this problem,” said Nemhauser. “By taking the question of auxin response out of plants and reconstructing it — piece by piece — in yeast, we were able to find out the parts that matter most.”

Nemhauser’s team could introduce different auxin-response proteins into the modified yeast cells, each time measuring how they modified gene expression in the presence of auxin. Their experiments revealed the basic “code” of auxin signaling — how specific combinations of repressing or activating proteins can bind to auxin, DNA and one another to affect cellular behavior. For example, their yeast experiments show that the gene-activating protein ARF19 must bind to an identical protein to fully switch on genes. On the other hand, many gene-silencing proteins don’t need a partner to switch off genes.

These and other simple rules were only shown clearly in the yeast system developed by Nemhauser’s team. They shed light on the complex interplay within cells that produces clear auxin-mediated messages.

“These are a complicated combination of factors within cells that, when interpreted through this interplay, yield sophisticated output signals — like ‘Should this plant invest energy into making leaves or roots?'” said Nemhauser. “And it all begins with this complex dance between auxin and auxin-responding proteins.”

Nemhauser hopes this yeast-based tool, which she developed with 91̽��electrical engineering professor , will reveal more details of auxin’s actions in plant cells. And she hopes that knowledge will empower both farmers and plant geneticists in their quest to increase crop yields and resilience in the face of droughts and climate change.

“These tools could do so much, because biological systems are more complex than anything we could engineer,” said Nemhauser. “And with the right tools and knowledge of these hormone-signaling pathways, we will know exactly which changes — minimal and targeted — will produce desired traits in crops.”

Lead author on the paper is Edith Pierre-Jerome, who earned her doctorate in biology at 91̽��and is now a postdoctoral researcher at Duke University. Other co-authors are former 91̽��postdoctoral researcher and current Whitman College assistant professor Britney Moss, molecular and cellular biology graduate student Amy Lanctot and research technician Amber Hageman, who is now a 91̽��biology graduate student. The work was funded by the Paul G. Allen Family Foundation, the National Institutes of Health and the National Science Foundation.

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For more information, contact Nemhauser at 206-543-0753 and jn7@uw.edu.

Grant numbers: MCB-1411949, R01-GM107084

A study led by the 91̽�� shows that popular long-term drought estimates have a major flaw: They ignore the fact that plants will be less thirsty as carbon dioxide rises. The shows that shifts in how plants use water could roughly halve the extent of climate change-induced droughts.

“Plants matter,” said , a 91̽��assistant professor of atmospheric sciences and biology. “A number of studies assume that plant water needs are staying constant, when what we know about plants growing in lots of carbon dioxide suggests the opposite.”

Swann is lead author of the study published the week of Aug. 29 in the .

Recent studies have estimated that more than 70 percent of our planet will experience more drought as carbon dioxide levels quadruple from pre-industrial levels over about the next 100 years. But when Swann and her co-authors account for changes in plants’ water needs, this falls to 37 percent, with bigger differences concentrated in certain regions.

“It’s a significant effect,” Swann said.

The reason is that when Earth’s atmosphere holds more carbon dioxide, plants actually benefit from having more of the molecules they need to build their carbon-rich bodies. Plants take in carbon dioxide through tiny openings, called stomata, that cover their leaves. But as they draw in carbon dioxide, moisture escapes. When carbon dioxide is more plentiful, the stomata don’t need to be open for as long, and so the plants lose less water.  The plants thus draw less water from the soil through their roots.

Global climate models already account for these changes in plant growth. But many estimates of future drought use today’s standard indices, like the , which only consider atmospheric variables such as future temperature, humidity and precipitation.

“I had a very strong suspicion that you would get a different answer if you considered how the plants were responding,” Swann said.

The study compares today’s drought indices with ones that take into account changes in plant water use. It confirms that reduced precipitation will increase droughts across southern North America, southern Europe and northeastern South America. But the results show that in Central Africa and temperate Asia — including China, the Middle East, East Asia and most of Russia — water conservation by plants will largely counteract the parching due to climate change.

Planners will need accurate long-term drought predictions to design future water supplies, anticipate ecosystem stresses, project wildfire risks and decide where to locate agricultural fields.

“In some sense there’s an easy solution to this problem, which is we just have to create new metrics that take into account what the plants are doing,” Swann said. “We already have the information to do that; we just have to be more careful about ensuring that we’re considering the role of the plants.”

Is this good news for climate change? Although the drying may be less extreme than in some current estimates, droughts will certainly increase, researchers said, and other aspects of climate change could have severe effects on vegetation.

“There’s a lot we don’t know, especially about hot droughts,” Swann said. The same drought at a higher temperature might have more severe impacts, she noted, or might make plants more stressed and susceptible to pests.

“Even if droughts are not extremely more prevalent or frequent, they may be more deadly when they do happen,” she said.

The co-authors are Forrest Hoffman at Oak Ridge National Laboratory, Charles Koven at Lawrence Berkeley National Laboratory and James Randerson at the University of California, Irvine. The research was funded by the National Science Foundation and the U.S. Department of Energy.

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For more information, contact Swann at 206-616-0486 or aswann@uw.edu.

Grant numbers: NSF AGS-1321745, EF-1340649

Visitors to Seattle’s are in for a stinking treat, courtesy of the Department of Biology at the 91̽��. The conservatory has a young corpse lily while the university awaits the 2018 opening of a new greenhouse facility in the . The young plant, affectionately known as Dougsley, is set to blossom this week or next. Releasing its stench the first night after opening, the foul scent will dissipate in subsequent days until the flower fades.

Also known as the titan arum, corpse lilies are aptly named. Native to Sumatra, their open flowers give off an odor not unlike rotting carrion. For the 12 to 24 hours that the flower remains open, this fetid fragrance recruits flies and beetles to pollinate the flower ensuring the production of the next generation. The flower also generates heat to help spread the volatile chemicals that make up their signature stinking stench. One plant produces both male and female flowers, which mature at separate times to prevent self-pollination.

Corpse lilies boast the largest unbranched inflorescence — or flowering stem — of all flowering plants. Before opening, a single inflorescence can reach a height of nearly 10 feet. But corpse lilies must grow large enough to bloom as flowering takes a lot of energy, so plants can wait up to a decade before blooming. As of press time, young Dougsley’s inaugural inflorescence just over 23 inches and growing.

Dougsley takes its name from Doug Ewing, who managed the former greenhouse next to Kincaid Hall for 31 years before retiring in 2014. Ewing first brought corpse lilies to the greenhouse in the 1990s, and the UW’s first corpse flower opened in 1999. In 2004 two different corpse lilies bloomed at the same time, allowing Ewing to remove pollen from one plant — grown from a wild seed — and pollinate the flower of the other plant — grown from seed obtained from a German botanic garden. Dougsley is the first plant from that pairing to become sufficiently mature to bloom.

The Life Sciences Complex is going up on the former site of the UW’s greenhouse, demolished earlier this year so construction could begin. the bulk of the greenhouse’s bounty until the new facility is ready.

For updates on Dougsley’s progress toward an evening bloom — its preferred time of the day to open — check the Volunteer Park Conservatory’s .

While humans are alone in their struggle to balance work and Netflix, all creatures wrestle with proper timing. With limited resources, organisms are pressed to use time wisely in all aspects of their lives. As researchers recently discovered, this struggle even extends to something as sweet and pleasant as the fragrant scent of a garden flower.

A team of has identified a key mechanism plants use to decide when to release their floral scents to attract pollinators. Their findings,  by the , connect the production and release of these fragrant chemicals to the innate circadian rhythms that pulse through all life on Earth.

The researchers studied these questions in the common garden petunia. This white-flowered hybrid releases an aromatic, sweet-smelling fragrance in the evening to attract insect pollinators, such as hawk moths.

“Plants emit these scents when they want to attract their pollinators,” said , 91̽��associate professor of biology and senior author on the paper. “It makes sense that they should time this with when the pollinators will be around.”

discovered a major gene that controls when the petunia releases its fragrance. The gene – known by its acronym LHY – is found in many plant species and is a key component of the plant “circadian clock.”

Biologists have long recognized that creatures like plants, humans and even tiny bacteria all have circadian clocks – genes that keep their cells synchronized to the 24-hour cycle of life on Earth. These genes regulate cellular activities based on the time of day. Researchers had previously shown that LHY is a component of the circadian clock in other flowering plants, but this week’s paper marks the first time biologists have connected LHY activity to flower scent.

“Now we’re finding out what the bridge is between the circadian clock and scent production and release,” said , a 91̽��doctoral student in biology and one of three lead authors on the paper.

Since no one had ever studied the LHY gene in petunias, Fenske and his fellow researchers gathered basic information about LHY to show that it has the same circadian functions as it does in other plant species. Many circadian clock genes are only active at specific times of the day, when they influence the activity of other genes that control what cells are doing. The researchers in Imaizumi’s lab discovered that the petunia LHY gene is most active in the morning, at the opposite time of day when the petunia releases its fragrant evening scent.

Imaizumi and his team hypothesized that LHY’s morning activity might repress the production of scented chemicals. When they prolonged LHY’s activity into the evening, the petunias didn’t release their fragrant chemicals at all.

“That was perfect,” said Imaizumi. “It is exactly what I would hope to see.”

If LHY’s activity truly did have a negative effect on scent production, then petunia plants that lacked the LHY gene’s burst of morning activity might produce and release their scents earlier in the day. Fenske and his colleagues created petunia plants with reduced LHY activity. Those plants produced and released fragrant chemicals four to eight hours earlier in the day.

Imaizumi’s team even discovered how LHY represses floral scent production. It interferes with the activity of ODO1, another petunia gene that promotes the production and release of floral scents. By repressing ODO1 activity early in the day, LHY stops the floral scent assembly line in its tracks. When the LHY gene becomes less active later in the day, ODO1 is able to ramp up production of the fragrant chemicals just in time for the evening aromatic release.

Since genes like LHY and ODO1 are present in most – if not all – flowering plants, Imaizumi and his team believe that the interactions between these two genes may be a common mechanism for a plant’s circadian clock to influence or control the production of fragrant floral scents. If so, then changes to the strength or timing of the LHY-ODO1 bridge may explain how flowers change the timing of scent production as they evolve.

Imaizumi and his team are now testing if pollinators have a preference between normal garden petunias or petunias with altered LHY activity. In time, these experiments may pave the way for scientists to improve the pollination efficiency of other plants, including important crop species.

“We think you can really change a plant’s success by changing these cues,” said Imaizumi.

The entire team was made up of researchers from the 91̽��biology department. Fenske’s fellow lead authors were technician Kristen Hewett Hazelton and undergraduate Andrew Hempton. Other authors included postdoctoral researcher , undergraduate Breanne Yamamoto and assistant professor of biology .

This research was funded by the National Institutes of Health (GM079712 and T32GM007270) and the National Science Foundation (IOS-1354159).

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For more information, contact Imaizumi at 206-543-8709 or takato@uw.edu.