Cold temperature during the reproductive stage often causes great yield loss of grain crops in subtropical and temperate regions. Previously we showed that the rice transcription factor bZIP73Jap plays an important role in cold adaptation at the seedling stage. Here we further demonstrate that bZIP73Jap also confers cold stress tolerance at the reproductive stage. bZIP73Jap was up‐regulated under cold treatment and predominately expressed in panicles at the early binucleate and flowering stages. bZIP73Jap forms heterodimers with bZIP71, and co‐expression of bZIP73Jap and bZIP71 transgenic lines significantly increased seed‐setting rate and grain yield under natural cold stress conditions. bZIP73Jap:bZIP71 not only repressed ABA level in anthers, but also enhanced soluble sugar transport from anthers to pollens and improved pollen grain fertility, seed‐setting rate, and grain yield. Interestingly, bZIP73Jap:bZIP71 also regulated the expression of qLTG3‐1Nip, and qLTG3‐1Nip overexpression lines greatly improved rice tolerance to cold stress during the reproductive stage. Therefore, our work establishes a framework for rice cold stress tolerance through the bZIP71‐bZIP73Jap‐qLTG3‐1Nip‐sugar transport pathway. Together with our previous work, our results provide a powerful tool for improving rice cold stress tolerance at both the seedling and the reproductive stages.
在亞熱帶和溫帶地區(qū)，生殖生長期的低溫常常造成糧食作物的大幅減產。先前我們發(fā)現(xiàn)，轉錄因子bZIP73Jap在水稻苗期的低溫適應中起著重要作用。在此，我們進一步證明bZIP73Jap在生殖期也具有耐寒性。bZIP73Jap在低溫處理后表達上調，主要在雙核早期和開花期的穗表達。bZIP73Jap與bZIP71形成異源二聚體，自然冷害條件下，共表達bZIP73Jap和bZIP71的轉基因株系顯著提高了結實率和籽粒產量。bZIP73Jap:bZIP71不僅抑制了花藥中的脫落酸水平，而且增強了可溶性糖從花藥向花粉的轉運，從而提高了花粉粒育性、結實率和籽粒產量。有意思的是，bZIP73Jap:bZIP71也調控qLTG3‐1Nip的表達，qLTG3‐1Nip過表達株系大幅提高了水稻生殖期對冷害的抗性。因此，我們的工作建立了一個水稻冷害抗性的框架，即bZIP71‐bZIP73Jap‐qLTG3‐1Nip‐糖轉運途徑?？傊?，結合先前的工作，我們的結果為提高水稻苗期和生殖期的耐寒性提供了一個有力的工具。