DELLA-mediated regulation of plant growth and oxidative stress tolerance: A role for ROS? – DELLAROS

Unlike animals, plants cannot escape adverse environments just by moving away. Plants live in fixed locations, and survive adversity by integrating growth responses to diverse environmental signals. For example, excess of salt in soil delays plant life-cycle and decreases yields. Therefore, understanding mechanisms regulating plant growth in adverse condition is of key strategic importance. Recent reports have highlight the importance of growth-repressing DELLA proteins (DELLAs). DELLAs are nuclear proteins that restrain 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 F-box proteins SLEPEPY (SLY1 and SLY2). 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 mechanism that explains how DELLAs restrain plant growth remains unknown. This proposal focuses on the role of DELLAs in the control of plant growth and tolerance to extreme conditions. Preliminary experiments suggest that DELLAs regulate adaptation to stress by modulating the accumulation in Reactive Oxygen Species (ROS) levels. When ROS accumulates, they have capacity to cause oxidative damage to proteins, DNA and lipids and thus to promote cell death. Intriguingly, there is now abundant evidence that ROS play roles in cell growth and that spatial regulation of ROS production is an important factor controlling plant form. The proposed research aims to determine whether GA-mediated plant growth and stress tolerance are coupled downstream of DELLAs and evaluating whether the ROS-signalling is the communal pathway.