Functional Transgenic Crops Research Unit, Genetically Modified Organism Research Center, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki 305-8602, Japan.
J Exp Bot. 2013 Dec;64(18):5429-41. doi: 10.1093/jxb/ert312. Epub 2013 Oct 23.
The heat shock protein 70 (Hsp70) chaperone system participates in protein folding and quality control of unfolded proteins. To examine the roles of co-chaperones in the rice Hsp70 chaperone system in the endoplasmic reticulum (ER), the functions of six ER-resident J-proteins (OsP58A, OsP58B, OsERdj2, OsERdj3A, OsERdj3B, and OsERdj7) in rice were investigated. The expression of OsP58B, OsERdj3A, and OsERdj3B was predominantly up-regulated in roots subjected to ER stress. This response was mediated by signalling through ATF6 orthologues such as OsbZIP39 and OsbZIP60, but not through the IRE1/OsbZIP50 pathway. A co-immunoprecipitation assay demonstrated that OsP58A, OsP58B, and OsERdj3B preferentially interact with the major OsBiP, OsBiP1, while OsERdj3A interacts preferentially with OsBiP5, suggesting that there are different affinities between OsBiPs and J-proteins. In the endosperm tissue, OsP58A, OsP58B, and OsERdj2 were mainly localized in the ER, whereas OsERdj2 was localized around the outer surfaces of ER-derived protein bodies (PB-Is). Furthermore, OsERdj3A was not expressed in wild-type seeds but was up-regulated in transgenic seeds accumulating human interleukin-7 (hIL-7). Since ERdj3A-green fluorescent protein (GFP) was also detected in vacuoles of callus cells under ER stress conditions, OsERdj3A is a bona fide vacuole-localized protein. OsP58A, OsP58B and OsERdj3A were differentially accumulated in transgenic plants expressing various recombinant proteins. These results reveal the functional diversity of the rice ER-resident Hsp70 system.
热休克蛋白 70（Hsp70）伴侣系统参与蛋白质折叠和未折叠蛋白质的质量控制。为了研究内质网（ER）中水稻 Hsp70 伴侣系统中共伴侣的作用，研究了六种 ER 驻留 J 蛋白（OsP58A、OsP58B、OsERdj2、OsERdj3A、OsERdj3B 和 OsERdj7）在水稻中的功能。在 ER 应激下，根中 OsP58B、OsERdj3A 和 OsERdj3B 的表达主要上调。这种反应是通过 ATF6 同源物（如 OsbZIP39 和 OsbZIP60）的信号转导介导的，但不是通过 IRE1/OsbZIP50 途径介导的。共免疫沉淀试验表明，OsP58A、OsP58B 和 OsERdj3B 优先与主要的 OsBiP、OsBiP1 相互作用，而 OsERdj3A 优先与 OsBiP5 相互作用，表明 OsBiP 和 J 蛋白之间存在不同的亲和力。在内胚乳组织中，OsP58A、OsP58B 和 OsERdj2 主要定位于 ER，而 OsERdj2 定位于 ER 衍生的蛋白质体（PB-Is）的外表面周围。此外，野生型种子中不表达 OsERdj3A，但在积累人白细胞介素-7（hIL-7）的转基因种子中上调。由于 ERdj3A-绿色荧光蛋白（GFP）也在 ER 应激条件下的愈伤组织细胞的液泡中检测到，因此 OsERdj3A 是一种真正的液泡定位蛋白。在表达各种重组蛋白的转基因植物中，OsP58A、OsP58B 和 OsERdj3A 差异积累。这些结果揭示了水稻 ER 驻留 Hsp70 系统的功能多样性。
