Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Plant biology discovery furthers scientists' understanding of plant growth and development


UC Riverside scientists discover auxin sensing and signaling complex on plant cell surface that explains why leaf epidermal cells have jigsaw puzzle-piece shapes

Auxin, a small molecule, is a plant hormone discovered by Charles Darwin about 100 years ago. Over the years that followed it became understood to be the most important and versatile plant hormone controlling nearly all aspects of plant growth and development, such as bending of shoots toward the source of light (as discovered by Darwin), formation of new leaves, flowers, and roots, growth of roots, and gravity-oriented growth. Just how a small molecule like auxin could play such a pivotal role in plants baffled plant biologists for decades.

Leaf Cells

The lab of Zhenbiao Yang, a professor of cell biology at UC Riverside, has made a discovery that helps explain why leaf epidermal cells have jigsaw puzzle-piece shapes.

Credit: Yang Lab, UC Riverside.

Then, about ten years ago, an auxin sensing and signaling system was discovered in the cell's nucleus, but it could not explain all the diverse roles of auxin.

Now, plant cell biologists at the University of California, Riverside have discovered a new auxin sensing and signaling complex, one that is localized on the cell surface rather than in the cell's nucleus. The discovery provides new insights into the mode of auxin action, the researchers say.

"This is a new milestone in auxin biology and will ignite interest in the field," said Zhenbiao Yang, a professor of cell biology in the Department of Botany and Plant Sciences, and the leader of the research project. "Our findings conclusively demonstrate the existence of an extracellular auxin sensing system in plants, which had long been proposed but remained elusive. Further, we have uncovered the decades-long mystery of how ABP1, an auxin-binding protein, works to control plant developmental processes."

ABP1 was identified more than 40 years ago, but its role was hotly debated among plant biologists because its mode of action remained unclear — until the recent discovery by Yang's team.

The team also showed that the cell surface auxin sensing system involves "transmembrane receptor kinases" (TMKs) — enzymes widespread throughout eukaryotes that typically act as cell surface sensors for extracellular stimuli and translate them into intracellular responses.

"This breakthrough discovery of the cell surface ABP1/TMK auxin sensing system dramatically elevates the level of our understanding of how auxin plays diverse roles," said Natasha Raikhel, a distinguished professor of plant cell biology at UC Riverside, who was not involved in the research. "This signaling mechanism now serves as a paradigm for elucidating the molecular mechanisms underlying various auxin-modulated developmental processes and patterns. In addition to their major impact on the field of plant development and morphogenesis and plant signal transduction, Yang's discoveries also provide novel means of engineering plants with desired morphological traits and growth patterns."

Study results appear in the Feb. 28 issue of Science.

Yang's lab has been studying molecular mechanisms for the formation of the jigsaw puzzle-piece shape of pavement cells in leaf epidermis of the Arabidopsis plant, a small flowering plant widely used in plant biology laboratories as a model organism. It is the interlocking feature of these cells that provides the required physical strength and integrity for flat, thin leaves.

In previous work, the lab found that auxin activated the formation of the puzzle piece shape through ABP1 and ABP1-dependent activation of "ROP GTPases," which are pivotal regulatory proteins that act as a molecular switch in gating incoming signals from the cell surface. It was unclear, however, whether ABP1 was a cell surface auxin receptor. Also, just how it led to the activation of ROP GTPases remained unknown.

"But now we have identified a family of TMKs that physically and functionally interact with ABP1 to perceive and transduce auxin signal at the cell surface," Yang said. "We show that ABP1 and TMKs form a new auxin sensing complex at the cell surface and that TMKs transmit extracellular auxin signals to ROP GTPases located just inside of the cell membrane. This novel auxin sensing and signaling system makes possible the formation of the jigsaw shape of leaf epidermal cells and many other auxin-mediated processes."

Next, Yang's team plans to investigate whether there are additional components in the cell surface auxin sensing complex, what specific pathways are regulated by the cell surface auxin sensor, and why plants need both the nuclear and extracellular auxin sensors.


Yang was joined in the study by researchers at UCR; the National University of Singapore; the Chinese Academy of Sciences; the University of Wisconsin; Ghent University, Belgium; the Institute of Science and Technology, Austria; the University of North Carolina, Chapel Hill; and Masaryk University, the Czech Republic.

The research was supported by a grant to Yang from the National Institute of General Medical Sciences.

The University of California, Riverside is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California's diverse culture, UCR's enrollment has exceeded 21,000 students. The campus opened a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual statewide economic impact of more than $1 billion. A broadcast studio with fiber cable to the AT&T Hollywood hub is available for live or taped interviews. UCR also has ISDN for radio interviews. To learn more, call (951) UCR-NEWS.

Iqbal Pittalwala | EurekAlert!

Further reports about: Eukaryotes GTPases Kinases ROP Riverside leaf cells mechanisms plant cells processes receptor

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Reliable in-line inspections of high-strength automotive body parts within seconds

Nondestructive material testing (NDT) is a fast and effective way to analyze the quality of a product during the manufacturing process. Because defective materials can lead to malfunctioning finished products, NDT is an essential quality assurance measure, especially in the manufacture of safety-critical components such as automotive B-pillars. NDT examines the quality without damaging the component or modifying the surface of the material. At this year's Blechexpo trade fair in Stuttgart, Fraunhofer IZFP will have an exhibit that demonstrates the nondestructive testing of high-strength automotive body parts using 3MA. The measurement results are available in a matter of seconds.

To minimize vehicle weight and fuel consumption while providing the highest level of crash safety, automotive bodies are reinforced with elements made from...

Im Focus: Kick-off for a new era of precision astronomy

The MICADO camera, a first light instrument for the European Extremely Large Telescope (E-ELT), has entered a new phase in the project: by agreeing to a Memorandum of Understanding, the partners in Germany, France, the Netherlands, Austria, and Italy, have all confirmed their participation. Following this milestone, the project's transition into its preliminary design phase was approved at a kick-off meeting held in Vienna. Two weeks earlier, on September 18, the consortium and the European Southern Observatory (ESO), which is building the telescope, have signed the corresponding collaboration agreement.

As the first dedicated camera for the E-ELT, MICADO will equip the giant telescope with a capability for diffraction-limited imaging at near-infrared...

Im Focus: Locusts at the wheel: University of Graz investigates collision detector inspired by insect eyes

Self-driving cars will be on our streets in the foreseeable future. In Graz, research is currently dedicated to an innovative driver assistance system that takes over control if there is a danger of collision. It was nature that inspired Dr Manfred Hartbauer from the Institute of Zoology at the University of Graz: in dangerous traffic situations, migratory locusts react around ten times faster than humans. Working together with an interdisciplinary team, Hartbauer is investigating an affordable collision detector that is equipped with artificial locust eyes and can recognise potential crashes in time, during both day and night.

Inspired by insects

Im Focus: Physicists shrink particle accelerator

Prototype demonstrates feasibility of building terahertz accelerators

An interdisciplinary team of researchers has built the first prototype of a miniature particle accelerator that uses terahertz radiation instead of radio...

Im Focus: Simple detection of magnetic skyrmions

New physical effect: researchers discover a change of electrical resistance in magnetic whirls

At present, tiny magnetic whirls – so called skyrmions – are discussed as promising candidates for bits in future robust and compact data storage devices. At...

All Focus news of the innovation-report >>>



Event News

EHFG 2015: Securing healthcare and sustainably strengthening healthcare systems

01.10.2015 | Event News

Conference in Brussels: Tracking and Tracing the Smallest Marine Life Forms

30.09.2015 | Event News

World Alzheimer`s Day – Professor Willnow: Clearer Insights into the Development of the Disease

17.09.2015 | Event News

Latest News

Unexpected information about Earth's climate history from Yellow River sediment

09.10.2015 | Earth Sciences

Single atom alloy platinum-copper catalysts cut costs, boost green technology

09.10.2015 | Life Sciences

Indefatigable Hearing

09.10.2015 | Life Sciences

More VideoLinks >>>