State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
Plant Mol Biol. 2014 Jan;84(1-2):19-36. doi: 10.1007/s11103-013-0115-3. Epub 2013 Aug 6.
The bZIP transcription factor (TF) family plays an important role in the abscisic acid (ABA) signaling pathway of abiotic stress in plants. We here report the cloning and characterization of OsbZIP71, which encodes a rice bZIP TF. Functional analysis showed that OsbZIP71 is a nuclear-localized protein that specifically binds to the G-box motif, but has no transcriptional activity both in yeast and rice protoplasts. In yeast two-hybrid assays, OsbZIP71 can form both homodimers and heterodimers with Group C members of the bZIP gene family. Expression of OsbZIP71 was strongly induced by drought, polyethylene glycol (PEG), and ABA treatments, but repressed by salt treatment. OsbZIP71 overexpressing (p35S::OsbZIP71) rice significantly improved tolerance to drought, salt and PEG osmotic stresses. In contrast, RNAi knockdown transgenic lines were much more sensitive to salt, PEG osmotic stresses, and also ABA treatment. Inducible expression (RD29A::OsbZIP71) lines were significantly improved their tolerance to PEG osmotic stresses, but hypersensitivity to salt, and insensitivity to ABA. Real-time PCR analysis revealed that the abiotic stress-related genes, OsVHA-B, OsNHX1, COR413-TM1, and OsMyb4, were up-regulated in overexpressing lines, while these same genes were down-regulated in RNAi lines. Chromatin immunoprecipitation analysis confirmed that OsbZIP71 directly binds the promoters of OsNHX1 and COR413-TM1 in vivo. These results suggest that OsbZIP71 may play an important role in ABA-mediated drought and salt tolerance in rice.
bZIP 转录因子（TF）家族在植物非生物胁迫的脱落酸（ABA）信号通路中发挥重要作用。我们在此报道了 OsbZIP71 的克隆和特征，它编码一个水稻 bZIP TF。功能分析表明，OsbZIP71 是一种核定位蛋白，特异性结合 G-框基序，但在酵母和水稻原生质体中均没有转录活性。在酵母双杂交测定中，OsbZIP71 可以与 bZIP 基因家族的 C 组成员形成同源二聚体和异源二聚体。OsbZIP71 的表达受干旱、聚乙二醇（PEG）和 ABA 处理强烈诱导，但受盐处理抑制。过表达 OsbZIP71（p35S::OsbZIP71）的水稻显著提高了对干旱、盐和 PEG 渗透胁迫的耐受性。相比之下，RNAi 敲低转基因系对盐、PEG 渗透胁迫以及 ABA 处理更为敏感。诱导表达（RD29A::OsbZIP71）系显著提高了对 PEG 渗透胁迫的耐受性，但对盐敏感，对 ABA 不敏感。实时 PCR 分析显示，非生物胁迫相关基因 OsVHA-B、OsNHX1、COR413-TM1 和 OsMyb4 在过表达系中上调，而在 RNAi 系中下调。染色质免疫沉淀分析证实 OsbZIP71 可在体内直接结合 OsNHX1 和 COR413-TM1 的启动子。这些结果表明，OsbZIP71 可能在 ABA 介导的水稻耐旱和耐盐性中发挥重要作用。
