Genetic Analysis of Osmotic Stress Signal Transduction in Plants

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Osmotic stress caused by drought and salinity has been a major selective force in plant evolution and an important factor limiting crop productivity. Understanding the mechanisms by which plants detect and respond to osmotic stress is important for basic plant biology and for crop improvement. Previous studies suggested that plant adaptation to osmotic stress is governed by a complex network of regulatory pathways, but most of the key components in these pathways remain to be identified. This project continues previous effort in using Arabidopsis mutants to identify such regulatory components. Several Arabidopsis mutants impaired in osmotic stress-responsive gene expression were recovered from a genetic screen by luciferase imaging using plants that express the RD29A-LUC (firefly luciferase under control of the stress-inducible RD29A promoter) transgene. Some of the mutations have been isolated through map-based cloning, which provided significant new insights into osmotic stress responses in plants. For example, cloning of SAD1 revealed the involvement of RNA metabolism in osmotic stress signaling. This research is based on such findings and is aimed at identifying new regulatory components in osmotic stress signal transduction. Specific aims include the cloning and characterization of two new genetic loci involved in osmotic stress signaling, and the identification of genetic suppressors of existing mutants such as sad1.