Arabidopsis PYL8 gene Plays a Role in Drought Tolerance

Abstract

The phytohormone abscisic acid (ABA) plays an important role in developmental processes and stress responses. Recent identification of soluble ABA receptors, PYRABACTIN RESISTANCE1 (PYR1)/PYR1-LIKEs(PYLs)/REGULATORY COMPONENTS OF ABA RECEPTORs (RCARs), have provided in understanding the signaling mechanisms of ABA. One of PYLs, PYL8, is characterized in this study. Constitutive overexpression of PYL8 confers ABA hypersensitivity in Arabidopsis seed germination. Furthermore, the stomata of 35S:PYL8 plants had smaller guard cells and apertures than did wild type plants by approximately 80%, but RNAi plants had bigger guard cells and apertures than did wild plants by approximately 120%. Both overexpression and RNAi transgenic plants confirm that PYL8 positively regulates ABA signaling during germination and growth. Thus, 35S:PYL8 plants had tolerance to drought, and RNAi plants did not have resistance to drought. In order to understand the molecular mechanism of stress response by PYL8, expression of ABA-responsive genes in overexpression and RNAi plants were analyzed. HAB and AREB genes were more induced by ABA treatment in overexpressed plants. On the contrary, these genes were less induced in RNAi plants. Contribution of PYL8 to ABA signaling affects expression of ABA responsive genes and osmotic stress responses. These results show that PYL8 plays an important role in drought tolerance.

Keywords: PYL8, RCAR3, drought tolerance, ABA signaling