State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, 310027, Hangzhou, China.
State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, 200433, Shanghai, China.
Plant Mol Biol. 2021 May;106(1-2):21-32. doi: 10.1007/s11103-021-01123-1. Epub 2021 Feb 8.
This paper demonstrates that BBX28 and BBX29 proteins in Arabidopsis promote flowering in association with the CO-FT regulatory module at low ambient temperature under LD conditions. Flowering plants integrate internal developmental signals with external environmental stimuli for precise flowering time control. The expression of BBX29 is up-regulated by low temperature treatment, but the biological function of BBX29 in low temperature response is unknown. In the current study, we examined the biological role of BBX29 and its close-related protein BBX28 in flowering time control under long-day conditions. Although neither BBX28 single mutant nor BBX29 single mutant has a flowering-associated phenotype, the bbx28 bbx29 double mutant plants have an obvious delayed flowering phenotype grown at low ambient temperature (16°C) compared to the wild-type (WT) plants. The expression of FT and TSF was lower in bbx28 bbx29 double mutant plants than in wild-type plants at 16°C. Both BBX28 and BBX29 interact with CONSTANS (CO), an important flowering integrator that directly binds to the FLOWERING LOCUS T (FT) promoter. In the effector-reporter assays, transcriptional activation activity of CO on the FT promoter was reduced in bbx28 bbx29 double mutant plants compared to that in WT plants. Taken together, our results reveal that BBX28 and BBX29 are promoters of flowering in Arabidopsis, especially at low ambient temperature.
本文证明，在 LD 条件下，拟南芥中的 BBX28 和 BBX29 蛋白与 CO-FT 调控模块一起在低温下促进开花。开花植物将内部发育信号与外部环境刺激整合在一起，以实现精确的开花时间控制。BBX29 的表达受低温处理上调，但 BBX29 在低温响应中的生物学功能尚不清楚。在本研究中，我们研究了 BBX29 及其密切相关蛋白 BBX28 在长日照条件下控制开花时间的生物学作用。尽管 BBX28 单突变体或 BBX29 单突变体均没有与开花相关的表型，但与野生型（WT）植物相比，bbx28 bbx29 双突变体植物在低温（16°C）下的开花时间明显延迟。在 16°C 时，bbx28 bbx29 双突变体植物中 FT 和 TSF 的表达低于野生型植物。BBX28 和 BBX29 均与 CONSTANS（CO）相互作用，CO 是一个重要的开花整合因子，直接结合到开花 locus T（FT）启动子上。在效应物报告基因分析中，与 WT 植物相比，CO 对 FT 启动子的转录激活活性在 bbx28 bbx29 双突变体植物中降低。综上所述，我们的研究结果揭示了 BBX28 和 BBX29 是拟南芥开花的促进因子，特别是在低温条件下。
