Perales Mariano, Rodriguez Kevin, Snipes Stephen, Yadav Ram Kishor, Diaz-Mendoza Mercedes, Reddy G Venugopala
Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, Center for Plant Cell Biology, University of California, Riverside, CA 92521.
Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, Center for Plant Cell Biology, University of California, Riverside, CA 92521
Proc Natl Acad Sci U S A. 2016 Oct 11;113(41):E6298-E6306. doi: 10.1073/pnas.1607669113. Epub 2016 Sep 26.
Transcriptional mechanisms that underlie the dose-dependent regulation of gene expression in animal development have been studied extensively. However, the mechanisms of dose-dependent transcriptional regulation in plant development have not been understood. In Arabidopsis shoot apical meristems, WUSCHEL (WUS), a stem cell-promoting transcription factor, accumulates at a higher level in the rib meristem and at a lower level in the central zone where it activates its own negative regulator, CLAVATA3 (CLV3). How WUS regulates CLV3 levels has not been understood. Here we show that WUS binds a group of cis-elements, cis- regulatory module, in the CLV3-regulatory region, with different affinities and conformations, consisting of monomers at lower concentration and as dimers at a higher level. By deleting cis elements, manipulating the WUS-binding affinity and the homodimerization threshold of cis elements, and manipulating WUS levels, we show that the same cis elements mediate both the activation and repression of CLV3 at lower and higher WUS levels, respectively. The concentration-dependent transcriptional discrimination provides a mechanistic framework to explain the regulation of CLV3 levels that is critical for stem cell homeostasis.
动物发育过程中基因表达剂量依赖性调控的转录机制已得到广泛研究。然而，植物发育过程中剂量依赖性转录调控的机制尚不清楚。在拟南芥茎尖分生组织中，促进干细胞的转录因子WUSCHEL（WUS）在肋状分生组织中积累水平较高，而在中央区域积累水平较低，在中央区域它激活自身的负调控因子CLAVATA3（CLV3）。WUS如何调节CLV3水平尚不清楚。在这里，我们表明WUS以不同的亲和力和构象结合CLV3调控区域中的一组顺式元件，即顺式调控模块，在较低浓度下以单体形式存在，在较高水平下以二聚体形式存在。通过删除顺式元件、操纵WUS结合亲和力和顺式元件的同源二聚化阈值以及操纵WUS水平，我们表明相同的顺式元件分别在较低和较高WUS水平下介导CLV3的激活和抑制。浓度依赖性转录识别提供了一个机制框架来解释对干细胞稳态至关重要的CLV3水平的调控。
