State Key Laboratory of Genetic Engineering, Institute of Genetics, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai, 200433, China.
Plant J. 2015 Apr;82(2):302-14. doi: 10.1111/tpj.12819.
Plant height and flowering time are key agronomic traits affecting yield in rice (Oryza sativa). In this study, we investigated the functions in rice growth and development of OsNAC2, encoding a NAC transcription factor in rice. Transgenic plants that constitutively expressed OsNAC2 had shorter internodes, shorter spikelets, and were more insensitive to gibberellic acid (GA(3)). In addition, the levels of GAs decreased in OsNAC2 overexpression plants, compared with the wild-type. Moreover, flowering was delayed for approximately 5 days in transgenic lines. The transcription of Hd3a, a flowering-time related gene, was suppressed in transgenic lines. In addition, transgenic Arabidopsis plants expressing OsNAC2 were also more insensitive to GA(3). The expression levels of GA biosynthetic genes OsKO2 and OsKAO were repressed. The expression of OsSLRL, encoding a repressor in the GA signal pathway, and OsEATB, which encodes a repressor of GA biosynthesis, were both enhanced. Western blotting indicated that DELLA also accumulated at the protein level. Dual-luciferase reporter analyses, yeast one-hybrid assays and ChIP-qPCR suggested that OsNAC2 directly interacted with the promoter of OsEATB and OsKO2. Taken together, we proposed that OsNAC2 is a negative regulator of the plant height and flowering time, which acts by directly regulating key genes of the GA pathway in rice.
株高和开花时间是影响水稻（Oryza sativa）产量的主要农艺性状。本研究调查了水稻 NAC 转录因子 OsNAC2 在水稻生长发育中的功能。组成型表达 OsNAC2 的转基因植物具有更短的节间、更短的小穗，并且对赤霉素（GA（3））的敏感性降低。此外，与野生型相比，OsNAC2 过表达植物中的 GA 水平降低。此外，转基因株系的开花时间延迟了大约 5 天。与开花时间相关的基因 Hd3a 的转录在转基因株系中受到抑制。此外，表达 OsNAC2 的转基因拟南芥植物对 GA（3）也不敏感。GA 生物合成基因 OsKO2 和 OsKAO 的表达水平受到抑制。编码 GA 信号通路抑制剂的 OsSLRL 和编码 GA 生物合成抑制剂的 OsEATB 的表达均增强。Western blot 分析表明，DELLA 也在蛋白质水平上积累。双荧光素酶报告基因分析、酵母单杂交测定和 ChIP-qPCR 表明，OsNAC2 直接与 OsEATB 和 OsKO2 启动子相互作用。综上所述，我们提出 OsNAC2 是植物株高和开花时间的负调控因子，通过直接调节水稻 GA 途径的关键基因发挥作用。
