On April 30, 2020, Li Jiayang, academician team of Institute of genetics and developmental biology, Chinese Academy of Sciences, Xiong Guosheng, Professor team of Nanjing Agricultural University, Wang Bing, researcher of Institute of genetics, Chinese Academy of Sciences, Xie Qi, Institute of genetics, Chinese Academy of Sciences, Wang Yonghong and other plant cells published online the title of "strigolactone and karrikin signaling pathways expert ubiquitination and proteolysis of smxl2 to Regulate hypocotyl elongating in Arabidopsis thaliana.
Strigolactones (SLS) and karrikins (KARs) are related butene lactone signaling molecules that control plant development. In Arabidopsis, they are recognized by two closely related receptors, but they use the same F-box protein more axlellary growth H2 (max2) for signal transduction and target different members of the transcription repressor smax1-like (smxl) series for degradation. Both signals inhibited hypocotyl elongation, which led to the question of whether the signals converged or parallel. Here, we show that gr244do enhances the interaction between dwarf14 (D14) and smxl2, while Kar instead of gr24ent-5ds induces the association of karrikin insensive2 (kai2) with smax1 and smxl2. Both signals may trigger polyubiquitination and degradation of smxl2. Gr244do depends on D14, and gr24ent-5ds mainly depends on kai2. Smxl2 is very important for the hypocotyl response of gr244do. It has redundancy function in the hypocotyl response of sgr1 to gr24ent-5ds. In addition, gr244do induced the responses of d14-like2 (dlk2) and kar-up f-box1 (kuf1) through smxl2, while gr24ent-5ds induced the expression of these genes through smax1 and smxl2. These findings indicate that both SL and Kar can trigger polyubiquitination and degradation of smxl2, thus revealing unexpected but important convergence pathways in gene expression and hypocotyl elongation regulated by SL and Kar.
The project is supported by the National Natural Science Foundation of China, the special fund of the Chinese Academy of Sciences and the fund of the youth innovation promotion association of the Chinese Academy of Sciences.