Ghent University, Department of Plant Biotechnology and Bioinformatics, Technologiepark 71, 9052 Ghent, Belgium.
VIB Centre for Plant Systems Biology, Technologiepark 71, 9052 Ghent, Belgium.
J Exp Bot. 2023 Mar 28;74(6):1940-1956. doi: 10.1093/jxb/erad020.
Transcriptional networks are crucial to integrate various internal and external signals into optimal responses during plant growth and development. In Arabidopsis thaliana, primary root vasculature patterning and proliferation are controlled by a network centred around the basic Helix-Loop-Helix transcription factor complex, formed by TARGET OF MONOPTEROS 5 (TMO5) and LONESOME HIGHWAY (LHW), which control cell proliferation and division orientation by modulating the cytokinin response and other downstream factors. Despite recent progress, many aspects of the TMO5/LHW pathway are not fully understood. In particular, the upstream regulators of TMO5/LHW activity remain unknown. Here, using a forward genetics approach to identify new factors of the TMO5/LHW pathway, we discovered a novel function of the MYB-type transcription factor, MYB12. MYB12 physically interacts with TMO5 and dampens the TMO5/LHW-mediated induction of direct target gene expression, as well as the periclinal/radial cell divisions. The expression of MYB12 is activated by the cytokinin response, downstream of TMO5/LHW, resulting in a novel MYB12-mediated negative feedback loop that restricts TMO5/LHW activity, to ensure optimal cell proliferation rates during root vascular development.
转录网络对于整合植物生长和发育过程中的各种内部和外部信号至关重要。在拟南芥中，主根脉管系统的模式形成和增殖受到以基本螺旋-环-螺旋转录因子复合物为中心的网络的控制，该复合物由 MONOPTEROS 5（TMO5）和 LONESOME HIGHWAY（LHW）组成，通过调节细胞分裂和分裂方向来控制细胞增殖和分裂方向细胞分裂。尽管最近取得了进展，但 TMO5/LHW 途径的许多方面仍未完全理解。特别是，TMO5/LHW 活性的上游调节剂仍然未知。在这里，我们使用正向遗传学方法来鉴定 TMO5/LHW 途径的新因子，发现了 MYB 型转录因子 MYB12 的新功能。MYB12 与 TMO5 物理相互作用，抑制 TMO5/LHW 介导的直接靶基因表达的诱导，以及周缘/放射状细胞分裂。MYB12 的表达被 TMO5/LHW 下游的细胞分裂素反应激活，导致一个新的 MYB12 介导的负反馈回路，限制 TMO5/LHW 的活性，以确保根脉管发育过程中的最佳细胞增殖率。
