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Planta. 2012 Nov;236(5):1519-27. doi: 10.1007/s00425-012-1714-y. Epub 2012 Jul 24.

Expression of OsBiP4 and OsBiP5 is highly correlated with the endoplasmic reticulum stress response in rice.

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Functional Transgenic Crops Research Unit, Genetically Modified Organism Research Center, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki, 305-8602, Japan.


Binding protein (BiP) is a chaperone protein involved in the folding of secretory proteins in the ER lumen. OsBiP1 is constitutively expressed in various tissues, whereas the expression of OsBiP4 and OsBiP5 (OsBiP4&5) is not detected in any tissue under normal conditions. However, expression of OsBiP4&5 was highly and specifically activated under ER stress conditions induced by DTT treatment, OsBiP1 knockdown, OsBiP1 overexpression, OsIRE1 overexpression, or various exogenous recombinant proteins in transgenic rice. In contrast, OsBiP4&5 did not accumulate in OsIRE1 knockdown transgenic rice even after DTT treatment. When the subcellular localization of OsBiP4&5 was investigated in seed endosperm cells under the ER stress condition, OsBiP4&5 were localized to the ER, but did not participate in ER-derived protein body (PB-I) formation in a different manner to OsBiP1. These results indicate that OsBiP4&5 levels were positively correlated with stress levels in the ER. Taken together, these results suggest that OsBiP4&5 are ER stress-related BiP proteins that are regulated by OsIRE1/OsbZIP50 pathway and that they may have a distinct function from that of OsBiP1 in rice.

[Indexed for MEDLINE]

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