Bai Bo, Zhao Jie, Li Yaping, Zhang Fang, Zhou Jinjun, Chen Fan, Xie Xianzhi
Shandong Rice Research Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, PR China.
Shandong Rice Research Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, PR China; College of Life Science, Shandong Normal University, Jinan 250014, PR China.
Plant Sci. 2016 Jun;247:25-34. doi: 10.1016/j.plantsci.2016.02.017. Epub 2016 Feb 27.
B-box (BBX) proteins are zinc finger proteins containing B-box domains, which have roles in Arabidopsis growth and development. However, little is known concerning rice BBXs. Herein, we identified a rice BBX protein, Oryza sativa BBX14 (OsBBX14). OsBBX14 is highly expressed in flag leaf blades. OsBBX14 expression shows a diurnal rhythm under photoperiodic conditions and subsequent continuous white light. OsBBX14 is located in the nucleus and has transcriptional activation potential. OsBBX14-overexpression (OsBBX14-OX) lines exhibited delayed heading date under long-day (LD) and short-day (SD) conditions, whereas RNAi lines of OsBBX14 lines had similar heading dates to the WT. The florigen genes, Hd3a and RFT1, were downregulated in the OsBBX14-OX lines under LD and SD conditions. Under LD conditions, Hd1 was expressed higher in the OsBBX14-OX lines than in the wild type (WT), and the rhythmic expression of circadian clock genes, OsLHY and OsPRR1, was changed in OsBBX14-OX lines. Thus, OsBBX14 acts as a floral repressor by promoting Hd1 expression under LD conditions, probably because of crosstalk with the circadian clock. Under SD conditions, Ehd1 expression was reduced in OsBBX14-OX lines, but Hd1 and circadian clock gene expressions were unaffected, indicating that OsBBX14 acts as a repressor of Ehd1. Our findings suggested that OsBBX14 regulates heading date differently under LD and SD conditions.
B-box（BBX）蛋白是一类含有B-box结构域的锌指蛋白，在拟南芥的生长发育过程中发挥作用。然而，关于水稻中的BBX蛋白，我们所知甚少。在此，我们鉴定出一种水稻BBX蛋白，即水稻BBX14（OsBBX14）。OsBBX14在剑叶中高表达。在光周期条件及随后的持续白光下，OsBBX14的表达呈现昼夜节律。OsBBX14定位于细胞核，具有转录激活潜能。在长日照（LD）和短日照（SD）条件下，过表达OsBBX14（OsBBX14-OX）的株系抽穗期延迟，而OsBBX14的RNA干扰株系的抽穗期与野生型相似。在LD和SD条件下，成花素基因Hd3a和RFT1在OsBBX14-OX株系中表达下调。在LD条件下，Hd1在OsBBX14-OX株系中的表达高于野生型（WT），并且生物钟基因OsLHY和OsPRR1的节律性表达在OsBBX14-OX株系中发生了改变。因此，在LD条件下，OsBBX14可能通过与生物钟相互作用，促进Hd1的表达，从而作为一种开花抑制因子发挥作用。在SD条件下，Ehd1在OsBBX14-OX株系中的表达降低，但Hd1和生物钟基因的表达未受影响，这表明OsBBX14是Ehd1的抑制因子。我们的研究结果表明，OsBBX14在LD和SD条件下对抽穗期的调控方式不同。
