A pepper RING-type E3 ligase, CaASRF1, plays a positive role in drought tolerance via modulation of CaAIBZ1 stability

Plants have evolved complex defense mechanisms to adapt and survive under adverse growth conditions. Abscisic acid (ABA) is a phytohormone that plays a pivotal role in the stress response, especially regulation of the stomatal aperture in response to drought. Here, we identified the pepper CaASRF1 (Capsicum annuum ABA Sensitive RING Finger E3 ligase 1) gene, which modulates drought stress tolerance via ABA-mediated signaling. CaASRF1 contains a C3H2C3-type RING finger domain, which functions as an E3 ligase by attaching ubiquitins to the target proteins. CaASRF1 expression was enhanced after exposure to ABA, drought and NaCl. Loss-of-function in pepper plants and gain-of-function in Arabidopsis plants revealed that CaASRF1 positively modulates ABA signaling and the drought stress response. Moreover, CaASRF1 interacted with and was associated with degradation of the bZIP transcription factor CaAIBZ1 (Capsicum annuum ASRF1-Interacting bZIP transcription factor 1). Contrary to CaASRF1 phenotypes, CaAIBZ1-silenced pepper and CaAIBZ1-overexpressing Arabidopsis exhibited drought-tolerant and drought-sensitive phenotypes, respectively. Taken together, our data indicate that CaASRF1 positively modulates ABA signaling and the drought stress response via modulation of CaAIBZ1 stability.