芥菜BjuWRKY75基因表达及其与开花整合子BjuFT互作

Expression of Brassica juncea BjuWRKY75 and its interactions with flowering integrator BjuFT

摘要:

芥菜(Brassica juncea)是十字花科芸薹属一年或二年生蔬菜，其产品器官的产量和品质会受到开花时间的影响。WRKY家族成员具有响应生物和非生物胁迫、发育调控和信号转导等作用。WRKY75是WRKY家族中能够调节开花的重要成员，但在芥菜中的开花调控机制还未见报道。本研究克隆了芥菜BjuWRKY75基因，发现其编码蛋白具有高度保守的WRKY结构域，属于Ⅱ类WRKY蛋白，与黑芥BniWRKY75同源性最高。BjuWRKY75在花中表达丰度显著高于叶和茎，并且在叶中表达较为稳定。BjuWRKY75定位于细胞核，能够与含有W-box应答元件的开花整合子BjuFT的启动子相互作用，且能转录激活下游基因表达。BjuWRKY75转入拟南芥可显著提早开花。综上说明，BjuWRKY75能够直接靶向BjuFT从而促进开花。这为深入研究BjuWRKY75开花分子调控奠定了基础。

Abstract:

Brassica juncea is a yearly or biennial vegetable in Brassica of Cruciferae. The yield and quality of its product organs are affected by flowering time. WRKY proteins family can respond to biological and abiotic stresses, developmental regulation and signal transduction. WRKY75 is an important member of WRKY family which can regulate flowering, but the flowering regulation mechanism in B. juncea has not been reported. In this study, a gene BjuWRKY75 in B. juncea was cloned, and the encoded-protein belonged to the group Ⅱ of WRKY protein with highly conserved domain. BjuWRKY75 had the highest homology with BriWRKY75 of Brassica nigra. The relative expression level of BjuWRKY75 in flowers was significantly higher than that in leaves and stems, and it was expressed stably in leaves. BjuWRKY75 protein was localized in the nucleus and interacted with the promoter of the flowering integrator BjuFT, which contained the W-box response element for the interaction between protein and DNA. Thus, it could transcriptionally activate the expression of the downstream genes. The overexpression of BjuWRKY75 in Arabidopsis led to earlier flowering significantly. In conclusion, BjuWRKY75 could directly target the promoter of BjuFT and accelerate flowering. These results may facilitate further study on the regulation of flowering molecules of BjuWRKY75.