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 轉(zhuǎn)錄因子家族在植物非生物脅迫的ABA信號(hào)途徑中扮演著一個(gè)重要的角色。這里我們報(bào)道了OsbZIP71的克隆和特性，它編碼一個(gè)水稻bZIP轉(zhuǎn)錄因子。功能分析顯示OsbZIP71是一個(gè)核定位蛋白，它能特異的結(jié)合到G-box基序上，但是在酵母和水稻原生質(zhì)體里沒(méi)有轉(zhuǎn)錄活性。酵母雙雜分析顯示OsbZIP71能夠和bZIP基因家族C組成員形成同源二聚體和異源二聚體。OsbZIP71的表達(dá)被干旱、聚乙二醇（PEG）和ABA誘導(dǎo)，但是被鹽抑制。過(guò)表達(dá)OsbZIP71 (p35S::OsbZIP71)水稻植株顯著提高了對(duì)干旱、鹽和PEG滲透脅迫的耐受性。相反，RNAi抑制的轉(zhuǎn)基因株系對(duì)鹽、PEG滲透脅迫和ABA處理是更敏感的。誘導(dǎo)表達(dá)(RD29A::OsbZIP71)株系顯著提高水稻對(duì)PEG滲透脅迫的耐受性，但是對(duì)鹽超敏感，對(duì)ABA是不敏感的。實(shí)時(shí)熒光定量PCR分析顯示這些非生物脅迫相關(guān)基因OsVHA-B、OsNHX1、COR413-TM1和 OsMyb4在過(guò)表達(dá)株系里表達(dá)上調(diào)，同時(shí)這些基因在RNAi株系里表達(dá)下調(diào)。染色質(zhì)免疫共沉淀技術(shù)分析證實(shí)了OsbZIP71在體內(nèi)直接結(jié)合到 OsNHX1 和 COR413-TM1的啟動(dòng)子上。這些結(jié)果表明了水稻OsbZIP71在ABA介導(dǎo)的干旱和鹽耐受性扮演著一個(gè)重要的角色。