The molecular chaperone binding protein gene participates in the constitutive function of plant growth and protects plant cells against stresses.In this study,we found that BnA7HSP70 overexpressed transgenic lines did not wilt and showed only a small decrease in water potential. However, the wild type lines showed a large decrease in leaf water potential. The transgenic plants had higher relative water content, better osmotic adjustment and less lipid membrane peroxidation. In addition, the leaves from the elevated levels of BnA7HSP70 in transgenic lines conferred tolerance to the glycosylation inhibitor tunicamycin during germination.BnA7HSP70 overexpression-mediated attenuation of stress-induced cell death was confirmed by the decreased per-centage of dead cell and the reduced induction of the senescence-associated marker gene BnCNX1. These phenotypes were accompanied by a delay in the induction of the cell death marker genes BnNRP,which are involved in transducing a cell death signal generated by ER stress and osmotic stress through the NRP (N-rich protein)-mediated signaling pathway. Enhanced expres-sion of BnA7HSP70 delayed unfold protein response and NRP pathway mediated chlorosis and the appearance of senes-cence-associated markers BnLSC222 and BnLSC54 in Brassica napus.These results suggest that overexpression of BnA7HSP70 in Brassica napus alleviate ER stress and osmotic stress-integrating cell death response confronted with water stress.%分子伴侣结合蛋白广泛参与植物生长发育过程, 在逆境下能够保护植物细胞免受胁迫.在甘蓝型油菜中超表达油菜含有HSP70热激蛋白结构域的分子伴侣基因BnA7HSP70,所得到的转基因植株在缺水条件下延缓萎蔫.通过生理生化实验证明, 干旱条件下转基因植株有着更高的相对含水量、更强的渗透调节能力和较低的脂质膜过氧化性.另外, 转基因植株的幼苗在萌发期表现出对糖基化酶抑制剂衣霉素处理的耐受性.Evans blue染色实验证明, 转基因植株逆境下叶片死亡细胞数目比非转基因植株减少, 叶片衰老相关标记基因 BnCNX1在转基因植株中下调表达证明, 超表达BnA7HSP70基因所介导的途径能够减轻逆境胁迫下的植株衰老, 保持叶片持绿性.在转基因植株中内质网和渗透胁迫产生的细胞死亡标记基因N-Rich蛋白BnNRP延迟表达证明,在油菜中增强BnA7HSP70基因的表达能够缓解未折叠蛋白途径(unfold protein response, UPR)和NRP (N-rich pathway)途径介导的叶片黄萎, 并降低油菜叶片失绿的标记基因BnLSC222和BnLSC54的表达.研究结果表明, 在油菜中超表达BnA7HSP70基因能够提高植株在干旱条件下内质网胁迫的耐受性.
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