Molecular responses to water stress inArabidopsis thaliana

Plants respond and adapt to environmental changes including drought, high salinity and low temperature. abscisic acid (ABA) plays important roles in these stress responses. A number of plant genes are induced by water stress, such as drought, high salinity and low temperature, and are thought to function in the stress tolerance and responses of the plant. At least four signal transduction pathways control these genes inArabidopsis thaliana: two are ABA-dependent, and two are ABA-independent. Acis-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 ABA-inducible MYC and MYB homologues are involved in ABA-responsive gene expression inarabidopsis. Roles of thesecis andtrans-acting factors in water stress responses are discussed. In addition, a number of genes for protein kinases, enzymes involved in phosphatidyl inositol metabolism (PI turnover) and transcription factors are also induced by water stress, and thought to be involved in the stress signal transduction cascades. Possible signaling processes in water stress response are discussed.