Kurepa Jasmina, Li Yan, Smalle Jan A
Plant Physiology, Biochemistry, Molecular Biology Program, Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, 40546, USA.
Plant J. 2014 Apr;78(1):157-68. doi: 10.1111/tpj.12458. Epub 2014 Mar 5.
The cytokinins play essential roles in the development and environmental responses of higher plants. Cytokinin signaling leads to the phosphorylation-dependent activation of two classes of Arabidopsis response regulators (RRs): the type-B RR (RRB) transcriptional activators that promote the expression of cytokinin response genes and the type-A RRs (RRAs) that are encoded by primary cytokinin response genes and function as response inhibitors. We show that cytokinin signaling increases the abundance of ARR1, a ubiquitously expressed RRB, by preventing its degradation by the 26S proteasome. We also show that the RRAs act to suppress ARR1 accumulation, thus providing an explanation for their inhibitory action in cytokinin signaling. Collectively, our results reveal an additional regulatory mechanism in the cytokinin response pathway that involves the cytokinin-dependent stability control of a major RRB response activator.
细胞分裂素在高等植物的发育和环境响应中发挥着重要作用。细胞分裂素信号传导导致两类拟南芥响应调节因子（RRs）的磷酸化依赖性激活：促进细胞分裂素响应基因表达的B型RR（RRB）转录激活因子，以及由主要细胞分裂素响应基因编码并作为响应抑制剂发挥作用的A型RRs（RRAs）。我们发现，细胞分裂素信号传导通过阻止26S蛋白酶体对普遍表达的RRB——ARR1的降解，从而增加了ARR1的丰度。我们还表明，RRAs可抑制ARR1的积累，从而解释了它们在细胞分裂素信号传导中的抑制作用。总体而言，我们的结果揭示了细胞分裂素响应途径中的一种额外调节机制，该机制涉及对主要RRB响应激活因子的细胞分裂素依赖性稳定性控制。
