Plants adapt their growth and development to protect themselves from detrimental conditions by triggering a variety of signaling pathways, including the activation of the ubiquitin-mediated protein degradation pathway. Endoplasmic reticulum (ER)-associated protein degradation (ERAD) is an important aspect of the ubiquitin-proteasome system, but only a few of the active ERAD components have been reported in plants to date.

Scientists in Dr. Qi Xie’s group, from the Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences, combined genetics, molecular biology and cell biology strategies to demonstrate that the Arabidopsis ubiquitin-conjugating enzyme, UBC32, which was a stress-induced functional ubiquitin conjugation enzyme (E2) localized on the ER membrane, connects the ERAD process and brassinosteroids (BR)-mediated growth promotion and salt stress tolerance. In vivo data showed that UBC32 was a functional ERAD component that affected the stability of the reported ERAD substrate barley MLO-12 mutant. UBC32 mutation caused the accumulation of bri1-5 and bri1-9, the mutant forms of the BR receptor, BRI1, which subsequently activated BR signal transduction. Further genetic and physiological data supported the contention that UBC32 plays a role in the BR-mediated salt stress response and that BR signaling is necessary for the plant to tolerate salt. Their data indicated a possible mechanism by which an ERAD component controls the growth and stress response of plants.

This work with the graduate student Feng Cui and postdoctor Dr. Lijing Liu as the co-first authors has been online published on The Plant Cell (DOI:10.1105/tpc.111.093062). This research was supported by grants from the Ministry of Science and Technology, National Natural Science Foundation of China and the Chinese Academy of Sciences.