AP2/ERF家族是一大组植物特异性转录因子,在许多生物过程中发挥重要作用,比如增长,发展,和非生物胁迫反应。OsDREB2B,AP2/ERF家族DREB亚组的脱水反应因子(DRE/CRT),与非生物应激反应有关,如寒冷,干旱,盐,和热应力,在拟南芥或水稻中。然而,其在调节水稻植物生长发育中的作用尚不清楚。在这项研究中,我们报道了OsDREB2B的新功能,对水稻的株高产生负调控作用。与野生型(WT)相比,OsDREB2B过表达(OE)水稻表现出矮化表型,例如降低植物高度,节间长度,和种子长度,以及谷物产量,而CRISPR/Cas9技术开发的敲除突变体表现出相似的表型。空间表达分析表明,OsDREB2B在叶鞘中高表达。外源GA3应用下,OsDREB2B表达被诱导,OsDREB2B-OE系的第二叶鞘的长度恢复到WT的长度。定位于水稻原生质体核的OsDREB2B充当转录激活剂,并通过直接结合其启动子来上调OsAP2-39。OsDREB2B-OE系通过下调七个GA生物合成基因和上调八个GA失活基因而不是GA信号基因来降低内源性生物活性GA水平。酵母双杂交和双分子荧光互补实验表明,OsDREB2B与OsWRKY21相互作用。总之,我们的研究表明,OsDREB2B通过调节GA代谢基因表达在水稻生长发育中起负作用,由OsAP2-39和OsWRKY21介导,从而降低GA含量和水稻株高。
The AP2/ERF family is a large group of plant-specific transcription factors that play an important role in many biological processes, such as growth, development, and abiotic stress responses. OsDREB2B, a dehydration responsive factor (DRE/CRT) in the DREB subgroup of the AP2/ERF family, is associated with abiotic stress responses, such as cold, drought, salt, and heat stress, in Arabidopsis or rice. However, its role in regulating plant growth and development in rice is unclear. In this study, we reported a new function of OsDREB2B, which negatively regulates plant height in rice. Compared with wild type (WT), OsDREB2B-overexpressing (OE) rice exhibited dwarf phenotypes, such as reduction in plant height, internode length, and seed length, as well as grain yield, while the knockout mutants developed by CRISPR/Cas9 technology exhibited similar phenotypes. Spatial expression analysis revealed that OsDREB2B was highly expressed in the leaf sheaths. Under exogenous GA3 application, OsDREB2B expression was induced, and the length of the second leaf sheath of the OsDREB2B-OE lines recovered to that of the WT. OsDREB2B localized to the nucleus of the rice protoplast acted as a transcription activator and upregulated OsAP2-39 by directly binding to its promoter. OsDREB2B-OE lines reduced endogenous bioactive GA levels by downregulating seven GA biosynthesis genes and upregulating eight GA deactivation genes but not GA signaling genes. The yeast two-hybrid assay and bimolecular fluorescence complementation assay showed that OsDREB2B interacted with OsWRKY21. In summary, our study suggests that OsDREB2B plays a negative role in rice growth and development by regulating GA metabolic gene expression, which is mediated by OsAP2-39 and OsWRKY21, thereby reducing GA content and rice plant height.