| iCal Calendar Event Reminder | 11:00 - 12:30 | Thursday, December 11, 2008 |
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| Event Text: | Dr. Patrick Achard Institut de Biologie Mol??culaire des Plantes Strasbourg FRANCE |
| Event Date: | Thursday, December 11, 2008 |
| Event Time: | 11:00 - 12:30 |
| Popup Text: | "A role for GA in plant stress acclimation" ABSTRACT Dr Patrick Achard Institut de Biologie Mol??culaire des Plantes, 67084 Strasbourg, France Correspondence: Patrick.achard@ibmp-ulp.u-strasbg.fr Plants live in fixed locations, and survive adversity by integrating growth responses to diverse environmental signals. For example, an excess of salt in the soil delays plant life-cycle and decreases yields. Therefore, understanding mechanisms regulating plant growth in adverse conditions is of key strategic importance. Recent reports have highlighted the importance of growth-repressing DELLA proteins (DELLAs). DELLAs (GAI, RGA, RGL1, RGL2 and RGL3 in Arabidopsis) are nuclear proteins that restrain the cell expansion that drives plant growth. The phytohormone gibberellin (GA) stimulates growth by promoting the destruction of DELLAs by the proteasome via a specific SCF E3 ubiquitin ligase involving the SLEEPY F-box proteins. Moreover, the stress response phytohormone ethylene and abscisic acid also control DELLA restraint. Finally, the growth restraint conferred by DELLAs is beneficial to plants by promoting their survival under adverse conditions. Therefore it has been proposed that DELLAs permit flexible and appropriate growth in response to environmental changes. However, the relationship between these survival and growth-regulatory mechanisms was previously unknown. We now show that both mechanisms are dependent upon control of the accumulation of reactive oxygen species (ROS). ROS are small molecules generated during development and in response to stress that play diverse roles as eukaryotic intracellular second messengers. We show that Arabidopsis DELLAs cause ROS levels to remain low following either biotic or abiotic stress, thus delaying cell death and promoting tolerance. In accord with recent demonstrations that R OS control root cell expansion, we also show that DELLAs regulate root hair growth via a ROS-dependent mechanism. We therefore propose that environmental variability regulates DELLA activity, and that DELLAs in turn couple the downstream regulation of plant growth and stress tolerance through modulation of ROS levels. |