Identification of Roles for Arabidopsis thaliana RING-Type Ubiquitin Ligase XBAT35.2 and its Substrate Accelerated Cell Death11 (ACD11) in Abiotic Stress Tolerance

Abstract

To survive adverse environmental conditions plants utilize various mechanisms including the production of the hormone abscisic acid, which promote cellular changes to ameliorate the negative effects of abiotic stress. The Ubiquitination Proteasome System is used to regulate stress signaling to properly initiate and terminate responses. Ubiquitination involves E3s that govern substrate selection. Here, we demonstrate that the E3 XBAT35.2 and its substrate ACD11 are involved in the abiotic stress tolerance. XBAT35.2 levels, and levels of ACD11 increase in response to stress. Surprisingly, prolonged exposure to stress leads to a decrease in ACD11 abundance. xbat35-1 mutants and plants overexpressing ACD11 display enhanced stress tolerance. Also, XBAT35.2 promotes proteasome-dependent degradation of ACD11 under stress conditions. We propose that while ACD11 promotes tolerance, stress-stabilized XBAT35.2 functions to attenuate/terminate ACD11-mediated responses. This study improves our understanding of XBAT35.2 and ACD11 function and may contribute knowledge to the development of stress tolerant crops.