We successfully identified a novel and unique OsbZIP transcription factor, OsbZIP09, whose mutants exhibited longer seeds and less severe pre-harvest sprouting than the wild type, but shared similar germination rate as the wild type under normal germination conditions. The expression of OsbZIP09 was induced by abscisic acid (ABA) and declined as the germination process. As a nucleus-localized transcription factor, the conserved binding motif of OsbZIP09 was identified via DNA affinity purification sequencing technique. Further evidences indicated that OsbZIP09 directly enhanced the expression of ABA catabolism gene ABA8ox1, thus reducing ABA accumulation. In addition, OsbZIP09 also directly bound to the promoter of LEA3 gene to inhibit its expression, thus further alleviating the suppressive effect of ABA on seed germination. These results demonstrated that OsbZIP09 likely functions as a brake of the ABA pathway to attenuate the inhibitory effect of ABA on rice seed germination via dual strategies.

我们成功鉴定了一种新颖独特的 OsbZIP 转录因子 OsbZIP09，其突变体与野生型相比，种子更长，收获前发芽较轻，但在正常发芽条件下与野生型具有相似的发芽率。OsbZIP09的表达受到脱落酸（ABA）的诱导，并随着萌发过程而下降。作为细胞核定位的转录因子，OsbZIP09 的保守结合基序是通过 DNA 亲和纯化测序技术鉴定的。进一步的证据表明，OsbZIP09直接增强了ABA分解代谢基因ABA8ox1的表达，从而减少了ABA的积累。此外，OsbZIP09 还直接与LEA3的启动子结合基因抑制其表达，从而进一步减轻 ABA 对种子萌发的抑制作用。这些结果表明，OsbZIP09 可能作为 ABA 途径的制动器，通过双重策略减弱 ABA 对水稻种子萌发的抑制作用。