Yang Xiaorui, Bai Yang, Shang Jianxiu, Xin Ruijiao, Tang Wenqiang
Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang, 050016, China.
School of Computer Science and Technology, Harbin Institute of Technology, Harbin, 150001, China.
Plant Cell Environ. 2016 Sep;39(9):1994-2003. doi: 10.1111/pce.12763. Epub 2016 Jul 15.
Brassinosteroids (BRs) and abscisic acid (ABA) are plant hormones that antagonistically regulate many aspects of plant growth and development; however, the mechanisms that regulate the crosstalk of these two hormones are still not well understood. BRs regulate plant growth and development by activating BRASSINAZOLE RESISTANT 1 (BZR1) family transcription factors. Here we show that the crosstalk between BRs and ABA signalling is partially mediated by BZR1 regulated gene expression. bzr1-1D is a dominant mutant with enhanced BR signalling; our results showed that bzr1-1D mutant is less sensitive to ABA-inhibited primary root growth. By RNA sequencing, a subset of BZR1 regulated ABA-responsive root genes were identified. Of these genes, the expression of a major ABA signalling component ABA INSENSITIVE 5 (ABI5) was found to be suppressed by BR and by BZR1. Additional evidences showed that BZR1 could bind strongly with several G-box cis-elements in the promoter of ABI5, suppress the expression of ABI5 and make plants less sensitive to ABA. Our study demonstrated that ABI5 is a direct target gene of BZR1, and modulating the expression of ABI5 by BZR1 plays important roles in regulating the crosstalk between the BR and ABA signalling pathways.
油菜素甾醇（BRs）和脱落酸（ABA）是对植物生长发育诸多方面起拮抗调控作用的植物激素；然而，调控这两种激素相互作用的机制仍未完全明晰。BRs通过激活油菜素唑抗性1（BZR1）家族转录因子来调控植物生长发育。在此我们表明，BRs与ABA信号传导之间的相互作用部分是由BZR1调控的基因表达介导的。bzr1 - 1D是一个具有增强BR信号传导的显性突变体；我们的结果表明，bzr1 - 1D突变体对ABA抑制的初生根生长不太敏感。通过RNA测序，鉴定出了一组由BZR1调控的ABA响应根基因。在这些基因中，发现主要ABA信号组分ABA不敏感5（ABI5）的表达受到BR和BZR1的抑制。其他证据表明，BZR1能与ABI5启动子中的几个G - 盒顺式元件强烈结合，抑制ABI5的表达并使植物对ABA不太敏感。我们的研究表明，ABI5是BZR1的直接靶基因，并且BZR1对ABI5表达的调控在调节BR和ABA信号通路之间的相互作用中起重要作用。
