MOLECULAR RESPONSES TO WATER-STRESS IN ARABIDOPSIS-THALIANA

Plants respond and adapt to environmental changes including drought, h igh salinity and low temperature. Abscisic acid (ABA) plays important roles in these stress responses. A number of plant genes are induced b y water stress, such as drought, high salinity and low temperature, an d are thought to function in the stress tolerance and responses of the plant. At least four signal transduction pathways control these genes in Arabidopsis thaliana: two are ABA-dependent and two are ABA-indepe ndent A cis-acting element named DRE (Dehydration Responsive Element) is involved in one of the ABA-independent signal transduction pathways , and its DNA binding proteins have been characterized. Drought- and A BA-inducible MYC and MYB homologues are involved in ABA-responsive gen e expression in Arabidopsis. Roles of these cis and transacting factor s in water stress responses are discussed. In addition, a number of ge nes for protein kinases, enzymes involved in phosphatidyl inositol met abolism (PI turnover) and transcription factors are also induced by wa ter stress. and thought to be involved in the stress signal transducti on cascades. Possible signaling processes in water stress response are discussed.