Plant shoot branching is pivotal for developmental plasticity and crop yield. The formation of branch meristems is regulated by several key transcription factors including REGULATOR OF AXILLARY MERISTEMS1 (RAX1), RAX2, and RAX3. However, the regulatory network of shoot branching is still largely unknown. Here, we report the identification of EXCESSIVE BRANCHES1 (EXB1), which affects axillary meristem (AM) initiation and bud activity. Overexpression of EXB1 in the gain-of-function mutant exb1-D leads to severe bushy and dwarf phenotypes, which result from excessive AM initiation and elevated bud activities. EXB1 encodes the WRKY transcription factor WRKY71, which has demonstrated transactivation activities. Disruption of WRKY71/EXB1 by chimeric repressor silencing technology leads to fewer branches, indicating that EXB1 plays important roles in the control of shoot branching. We demonstrate that EXB1 controls AM initiation by positively regulating the transcription of RAX1, RAX2, and RAX3. Disruption of the RAX genes partially rescues the branching phenotype caused by EXB1 overexpression. We further show that EXB1 also regulates auxin homeostasis in control of shoot branching. Our data demonstrate that EXB1 plays pivotal roles in shoot branching by regulating both transcription of RAX genes and auxin pathways.
新植物学家：福建农林揭示硫-TOR信号模块在激活地上部顶端分生组织中的作用
植物在地球硫循环过程中发挥重要作用，它们可以将地球中的无机硫转变为有机硫。但是目前关于植物如何感受硫元素并传递硫信号来影响植物的生长发育尚不清楚。
本研究通过 western blotting 和 RNA-seq分析解析了硫-TOR信号模块在调控地上部顶端分生组织发育过程中的作用。结果显示硫元素可以通过激活TOR激酶来促进细胞增殖从而促进了真叶的发育，这是一个平行于葡萄糖信号的过程。
此外，通过遗传以及代谢分析证实硫元素对生长发育的调控是一个独立于硫同化的过程。
TOR激酶对于激活地上部顶端分生组织的细胞增殖是必需的
最后，在表型分析的基础上通过转录组分析证实硫元素可以激活参与DNA复制、细胞增殖以及次生代谢相关基因的表达，这些基因的激活高度依赖于TOR激酶。
小结：本研究揭示了硫元素作为信号物质通过TOR激酶促进植物生长发育的分子机制
原文：Sulfate-TOR signalling controls transcriptional reprogramming for shoot apex activation
