Conservation of IRE1-Regulated bZIP74 mRNA Unconventional Splicing in Rice （Oryza sativa L.） Involved in ER Stress Responses  

作　　者：Sun-Jie Lu Zheng-Ting Yang Ling Sun Le Sun Ze-Ting Song Jian-Xiang Li 

机构地区：[1]State Key Laboratory of Genetic Engineering,Institute of Plant Biology,School of Life Sciences,Fudan University,Shanghai,200433,China

出　　处：《Molecular Plant》2012年第2期504-514,共11页分子植物（英文版）

基　　金：This project is funded by the National Natural Science Foundation of China （31070233, 31171157）, Shanghai Pujiang Talent Program （11PJ1400700）, and partly supported by the National Basic Research Program of China （973 Program, 2012CB910500）, all granted to J.X.L. ACKNOWLEDGMENTS We would also like thank Drs Yuhya Wakasa and Fumio Takaiwa for providing the OslREI transgenic rice seeds. No conflict of interest declared.

摘　　要：Protein folding in the endoplasmic reticulum （ER） is a fundamental process in plant cells that is vulnerable to many environmental stresses. When unfolded or misfolded proteins accumulate in the ER, the well-conserved unfolded protein response （UPR） is initiated to mitigate the ER stress by enhancing the protein folding capability and/or accelerating the ER-associated protein degradation. Here, we report the conservation of the activation mechanism of OsbZIP74 （also known as OsbZIP50）, an important ER stress regulator in monocot plant rice （Oryza sativa L.）. Under normal conditions, OsbZIP74 mRNA encodes a basic leucine-zipper transcription factor with a putative transmembrane domain. When treating with ER stress-inducing agents such as tunicamycin and DTT, the conserved double stem-loop structures of OsbZIP74 mRNA are spliced out. Thereafter, the resulting new OsbZIP74 mRNA produces the nucleus-localized form of OsbZIP74 protein, eliminating the hydrophobic region. The activated form of OsbZIP74 has transcriptional activation activity in both yeast cells and Arabidopsis leaf protoplasts. The induction of OsbZIP74 splicing is much suppressed in the OsIRE1 knock- down rice plants, indicating the involvement of OslRE1 in OsbZIP74 splicing. We also demonstrate that the unconventional splicing of OsbZIP74 mRNA is associated with heat stress and salicylic acid, which is an important plant hormone in systemic acquired resistance against pathogen or parasite.Protein folding in the endoplasmic reticulum （ER） is a fundamental process in plant cells that is vulnerable to many environmental stresses. When unfolded or misfolded proteins accumulate in the ER, the well-conserved unfolded protein response （UPR） is initiated to mitigate the ER stress by enhancing the protein folding capability and/or accelerating the ER-associated protein degradation. Here, we report the conservation of the activation mechanism of OsbZIP74 （also known as OsbZIP50）, an important ER stress regulator in monocot plant rice （Oryza sativa L.）. Under normal conditions, OsbZIP74 mRNA encodes a basic leucine-zipper transcription factor with a putative transmembrane domain. When treating with ER stress-inducing agents such as tunicamycin and DTT, the conserved double stem-loop structures of OsbZIP74 mRNA are spliced out. Thereafter, the resulting new OsbZIP74 mRNA produces the nucleus-localized form of OsbZIP74 protein, eliminating the hydrophobic region. The activated form of OsbZIP74 has transcriptional activation activity in both yeast cells and Arabidopsis leaf protoplasts. The induction of OsbZIP74 splicing is much suppressed in the OsIRE1 knock- down rice plants, indicating the involvement of OslRE1 in OsbZIP74 splicing. We also demonstrate that the unconventional splicing of OsbZIP74 mRNA is associated with heat stress and salicylic acid, which is an important plant hormone in systemic acquired resistance against pathogen or parasite.

关 键 词：mRNA unconventional splicing unfolded protein response bZIP transcription factor IRE1 heat stress salicylic acid （SA） Oryza sativa. 

分 类 号：Q785[生物学—分子生物学] S858.31[农业科学—临床兽医学]