Professor Jianxiang Liu - Zhejiang University

Professor Jianxiang Liu

Protein quality control and ER-associated thermotolerance in plants

The endoplasmic reticulum (ER) is essential not only for protein synthesis, folding, modification, and assembly in plant cells, but also for the synthesis of secondary metabolites such as waxes. Under environmental stress, misfolded proteins accumulate in the ER and trigger ER stress and the unfolded protein response (UPR). In this seminar, I will first introduce the importance of ER function and ER stress in plants, then focus on two regulatory mechanisms linked to thermotolerance in rice. First, we show that two rice SPP-like proteins, OsSPPL1/2, function in ER-associated degradation (ERAD). The UPR regulator OsbZIP50 directly upregulates OsSPPL1/2 under ER stress. OsSPPL1/2 localize in the ER, interact with the ERAD components OsDER1/2, and facilitate the degradation of a misfolded maize floury-2 fusion protein, ZmFL2m-GFP. Mutations in OsSPPL1/2 increase ER stress and heat sensitivity, while overexpression enhances ER stress tolerance and thermotolerance. Second, we report that modifying the heat stress-induced negative regulator NAT1 increases wax deposition and improves thermotolerance in rice. NAT1 directly inhibits bHLH110, which promotes wax biosynthetic genes CER1/CER1L under heat stress. NAT1-edited rice shows improved thermotolerance without yield penalty under normal conditions and increased seed setting rate and grain yield in field trials. Together, these findings highlight the importance of ER protein quality control and wax regulation in plant thermotolerance.