Abstract

High ambient temperature has important effects on the growth and development of plants. ELF3, a proposed thermosensor, downregulates the protein activity of growth promoting factor PIF4, and such an inhibitory effect is subjected to attenuation at hot temperature. However, how the ELF3 stability is regulated at hot temperature remains enigmatic. Here, we report the identification of XBAT31 as the E3 ligase which mediates ELF3 degradation in response to hot temperature in Arabidopsis. XBAT31 interacts with ELF3, ubiquitin ELF3 and promotes the degradation of ELF3 via the 26S proteasome. Mutation of XBAT31 results in increased accumulation of ELF3 and reduced hypocotyl elongation at warm temperature. In contrast, the overexpression of XBAT31 accelerates the degradation of ELF3 and promotes hypocotyl growth. In addition, XBAT31 interacts with the B-box protein BBX18, and the degradation of ELF3 mediated by XBAT31 depends on BBX18. Thus, our results reveal that XBAT31-mediated destruction of ELF3 represents an additional regulatory layer of complexity in temperature signaling during plant thermomorphogenesis.