Drought is a major environmental stress factor that affects the growth and development of plants, ultimately leading to growth reduction. Understanding how growth reduction and drought responses are coupled might enable us to find new ways to improve plant growth without endangering the physiological responses required for stress tolerance. Despite the progresses in the elucidation of drought stress signaling, and of the main pathways regulating plant development, the mechanisms by which stress response control growth are still unclear. We discovered that drought triggers high levels of post-translational modification (neddylation) of Cullin-RING ubiquitin ligases (CRLs), which control protein turnover via ubiquitination. This dramatic shift in CRL neddylation might be necessary to globally regulate CRL activity and promote the stress response, while shutting down positive growth regulators. This project thus proposes to elucidate this aspect by characterizing the protein stability and gene expression of selected effectors of growth and stress response in drought-stressed wild type and mutant plants, using Arabidopsis thaliana as a model organism. The results obtained within this project will advance our understanding of the signalling pathways that play a central role in plant adaptation and stress responses.
This project will contribute to determine how plants such as Arabidopsis can quickly switch from a "drought-tolerance" mode to a "growth promotion" mode. In fact, our preliminary data indicates that drought-stressed plants accumulated hyperneddylated CRLs already 30' from the start of the stimulus. CRLs could thus be among the direct drought and ABA targets and, by regulating the stability and activity of protein effectors, could inform critical decisions in a plant life cycle. The proposed experiments will thus place this project at the forefront of research in this field.
Although the trade-off between plant growth and drought stress tolerance greatly varies between plant species, some plants show both high levels of growth ability and drought stress tolerance (23), suggesting that overcoming the inherent trade-off between growth and drought stress tolerance in plants is indeed plausible.
Thus, the results obtained could also lay the conceptual basis for exploitation of these results in agriculture, where they can be used in strategies aiming at improving plant growth without compromising the physiological responses required for stress tolerance.
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