Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Newly discovered mechanism of plant hormone auxin acts the opposite way

04.04.2019

Auxin accumulation at the inner bend of seedling leads to growth inhibition rather than stimulation as in other plant tissues.

Increased levels of the hormone auxin usually promote cell growth in various plant tissues. Chinese scientists together with researchers from the Institute of Science and Technology Austria (IST Austria) have now shown that in special areas of the seedling, increased auxin levels trigger a different gene expression pathway leading to growth inhibition.


Increased auxin accumulation (blue areas) in the concave side of the apical hook of Arabidopsis thaliana

IST Austria – Marçal Gallemí Rovira/Eva Benková group

The discovery, published in the journal Nature, helps to explain the formation of the typical bend or so called apical hook that helps the seedling to break through the soil following germination.

Varied auxin concentrations mediate distinct developmental outcomes in different plant tissues. For instance, auxin accumulating in stem tissues triggers a gene expression pathway that ultimately leads to increased cell elongation resulting in stem growth.

A growth scenario, which cannot be explained in an analogous way, however, is the development of the apical hook that the early plant forms to protect its delicate growing apex when breaking through the soil. In the cells of the inner bend of the hook, i.e. the concave side, auxin accumulates; however, to grow into the form of a hook, the seedling’s shoot must grow less at the inner concave than on the outer convex side.

Scientists thus faced a paradox situation and asked themselves: Can auxin do something opposite from what it has been known to do in other parts of the plants?

One hormone—two different gene expressions

To solve the puzzle, the research group around Tongda Xu from the Chinese Academy of Sciences collaborated with IST Austria plant cell biologist Jiří Friml and his postdoc fellow Zuzana Gelová. By testing various mutants of the model plant Arabidopsis thaliana, the scientists could reveal a previously unknown gene expression pathway triggered by auxin accumulation and leading to the inhibition of growth at the concave side of the hook.

While the previously known pathway is located at the nucleus and involves the receptor protein TIR1 (Transport Inhibitor Response 1), this newly discovered pathway starts at the cell surface—and involves a different perception component, Transmembrane Kinase (TMK1), the function of which had been unclear.

A paradox and TMK1 explained

In the newly discovered mechanism, auxin activates TMK1 at the cell surface and triggers cleavage of the intracellular part of this protein. Within the cell, the cleaved part of TMK1 interacts with specific transcriptional repressors. While auxin degrades similar repressor proteins in the nucleus-based TIR1 pathway to trigger gene expression leading to cell growth, it stabilizes the repressors connected to the TMK1 pathway, resulting in growth inhibition rather than stimulation.

Thus, TIR1 and TMK1 interact with different subsets of transcriptional proteins and therefore facilitate auxin signaling by two different mechanisms, allowing the shoot to grow on one side, but not the other. Co-author Jiří Friml: “We have wanted to understand for a long time how TMK1 works as well as whether and how auxin accumulation can function in two different ways.

Thanks to our persistence and the major contributions of our Chinese colleagues, we now know both.” Starting from here, it would also be worthwhile to the scientists to understand the full repertoire of the developmental process beyond the apical hook controlled by this novel auxin signaling pathway.

IST Austria

The Institute of Science and Technology (IST Austria) is a PhD-granting research institution located in Klosterneuburg, 18 km from the center of Vienna, Austria. Inaugurated in 2009, the Institute is dedicated to basic research in the natural and mathematical sciences. IST Austria employs professors on a tenure-track system, postdoctoral fellows, and doctoral students. While dedicated to the principle of curiosity-driven research, the Institute owns the rights to all scientific discoveries and is committed to promote their use. The first president of IST Austria is Thomas A. Henzinger, a leading computer scientist and former professor at the University of California in Berkeley, USA, and the EPFL in Lausanne, Switzerland. The graduate school of IST Austria offers fully-funded PhD positions to highly qualified candidates with a bachelor's or master's degree in biology, neuroscience, mathematics, computer science, physics, and related areas. www.ist.ac.at

Wissenschaftliche Ansprechpartner:

Prof. Jiří Friml
+43 2243 9000 5401
jiri.friml@ist.ac.at

Originalpublikation:

Min Cao et al: “TMK1-mediated auxin signaling regulates differential growth of the apical hook”, Nature, DOI: http://dx.doi.org/10.1038/s41586-019-1069-7

Weitere Informationen:

https://ist.ac.at/research/research-groups/friml-group/ Website of the research group

Dr. Elisabeth Guggenberger | idw - Informationsdienst Wissenschaft

Further reports about: Auxin cell growth plant hormone plant hormone auxin plant tissues proteins

More articles from Life Sciences:

nachricht If Machines Could Smell ...
19.07.2019 | Fraunhofer-Institut für Produktionstechnik und Automatisierung IPA

nachricht Algae-killing viruses spur nutrient recycling in oceans
18.07.2019 | Rutgers University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Better thermal conductivity by adjusting the arrangement of atoms

Adjusting the thermal conductivity of materials is one of the challenges nanoscience is currently facing. Together with colleagues from the Netherlands and Spain, researchers from the University of Basel have shown that the atomic vibrations that determine heat generation in nanowires can be controlled through the arrangement of atoms alone. The scientists will publish the results shortly in the journal Nano Letters.

In the electronics and computer industry, components are becoming ever smaller and more powerful. However, there are problems with the heat generation. It is...

Im Focus: First-ever visualizations of electrical gating effects on electronic structure

Scientists have visualised the electronic structure in a microelectronic device for the first time, opening up opportunities for finely-tuned high performance electronic devices.

Physicists from the University of Warwick and the University of Washington have developed a technique to measure the energy and momentum of electrons in...

Im Focus: Megakaryocytes act as „bouncers“ restraining cell migration in the bone marrow

Scientists at the University Würzburg and University Hospital of Würzburg found that megakaryocytes act as “bouncers” and thus modulate bone marrow niche properties and cell migration dynamics. The study was published in July in the Journal “Haematologica”.

Hematopoiesis is the process of forming blood cells, which occurs predominantly in the bone marrow. The bone marrow produces all types of blood cells: red...

Im Focus: Artificial neural network resolves puzzles from condensed matter physics: Which is the perfect quantum theory?

For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.

Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...

Im Focus: Extremely hard yet metallically conductive: Bayreuth researchers develop novel material with high-tech prospects

An international research group led by scientists from the University of Bayreuth has produced a previously unknown material: Rhenium nitride pernitride. Thanks to combining properties that were previously considered incompatible, it looks set to become highly attractive for technological applications. Indeed, it is a super-hard metallic conductor that can withstand extremely high pressures like a diamond. A process now developed in Bayreuth opens up the possibility of producing rhenium nitride pernitride and other technologically interesting materials in sufficiently large quantity for their properties characterisation. The new findings are presented in "Nature Communications".

The possibility of finding a compound that was metallically conductive, super-hard, and ultra-incompressible was long considered unlikely in science. It was...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on UV LED Technologies & Applications – ICULTA 2020 | Call for Abstracts

24.06.2019 | Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

 
Latest News

Heat flow through single molecules detected

19.07.2019 | Physics and Astronomy

Heat transport through single molecules

19.07.2019 | Physics and Astronomy

Welcome Committee for Comets

19.07.2019 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>