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Signal transduction by IRE1‐mediated splicing of bZIP50 and other stress sensors in the endoplasmic reticulum stress response of rice
Author(s) -
Hayashi Shimpei,
Wakasa Yuhya,
Takahashi Hideyuki,
Kawakatsu Taiji,
Takaiwa Fumio
Publication year - 2012
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2011.04844.x
Subject(s) - rna splicing , xbp1 , endoplasmic reticulum , unfolded protein response , microbiology and biotechnology , biology , transcription factor , arabidopsis , messenger rna , signal transduction , transcription (linguistics) , gene , genetics , rna , linguistics , philosophy , mutant
Summary The endoplasmic reticulum (ER) stress sensor IRE1 transduces signals by inducing the unconventional splicing of mRNAs encoding key transcription factors: HAC1 in yeast and XBP1 in animals. However, no HAC1 or XBP1 homologues have been found in plants, and until recently the substrate for plant IRE1 has remained unknown. This study demonstrates that the Oryza sativa (rice) OsbZIP50 transcription factor, an orthologue of Arabidopsis AtbZIP60, is regulated by IRE1‐mediated splicing of its RNA. Despite the presence of a transcriptional activation domain, OsbZIP50 protein is not translocated into the nucleus efficiently in the absence of OsbZIP50 mRNA splicing. Unconventional splicing of OsbZIP50 mRNA causes a frame shift, which results in the appearance of a nuclear localization signal in the newly translated OsbZIP50. OsbZIP50 mRNA is spliced in a similar manner to HAC1 and XBP1 mRNAs; however, this splicing has very different effects on the translation products, a finding that shows the diversity of IRE1‐related transcription factors in eukaryotes. In addition, the expression of OsbZIP50 is affected by ER stress sensor proteins OsIRE1, OsbZIP39 and OsbZIP60. ER stress‐related genes differ with respect to their dependency on OsbZIP50 for their expression. The findings of this study improve our understanding of the molecular mechanisms underlying the plant ER stress response.