Department of Plant Systems Biology, VIB, 9052 Gent, Belgium; Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium; Institute of Science and Technology Austria, 3400 Klosterneuburg, Austria.
Department of Plant Systems Biology, VIB, 9052 Gent, Belgium; Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium.
Curr Biol. 2014 May 5;24(9):1031-7. doi: 10.1016/j.cub.2014.04.002. Epub 2014 Apr 24.
The plant hormones auxin and cytokinin mutually coordinate their activities to control various aspects of development [1-9], and their crosstalk occurs at multiple levels [10, 11]. Cytokinin-mediated modulation of auxin transport provides an efficient means to regulate auxin distribution in plant organs. Here, we demonstrate that cytokinin does not merely control the overall auxin flow capacity, but might also act as a polarizing cue and control the auxin stream directionality during plant organogenesis. Cytokinin enhances the PIN-FORMED1 (PIN1) auxin transporter depletion at specific polar domains, thus rearranging the cellular PIN polarities and directly regulating the auxin flow direction. This selective cytokinin sensitivity correlates with the PIN protein phosphorylation degree. PIN1 phosphomimicking mutations, as well as enhanced phosphorylation in plants with modulated activities of PIN-specific kinases and phosphatases, desensitize PIN1 to cytokinin. Our results reveal conceptually novel, cytokinin-driven polarization mechanism that operates in developmental processes involving rapid auxin stream redirection, such as lateral root organogenesis, in which a gradual PIN polarity switch defines the growth axis of the newly formed organ.
植物激素生长素和细胞分裂素相互协调它们的活动，以控制发育的各个方面[1-9]，并且它们的串扰发生在多个层面[10,11]。细胞分裂素介导的生长素运输的调节提供了一种有效的手段来调节植物器官中的生长素分布。在这里，我们证明细胞分裂素不仅控制生长素的整体流动能力，而且可能作为一个极化线索，并在植物器官发生过程中控制生长素流的方向性。细胞分裂素增强了特定极性域中 PIN 形成蛋白 1 (PIN1) 生长素转运蛋白的耗竭，从而重新排列细胞的 PIN 极性，并直接调节生长素的流动方向。这种选择性的细胞分裂素敏感性与 PIN 蛋白磷酸化程度相关。PIN1 磷酸模拟突变，以及调节 PIN 特异性激酶和磷酸酶活性的植物中的增强磷酸化，使 PIN1 对细胞分裂素脱敏。我们的结果揭示了一种概念新颖的、由细胞分裂素驱动的极化机制，该机制在涉及快速生长素流重定向的发育过程中起作用，例如侧根器官发生，其中逐渐的 PIN 极性转换定义了新形成器官的生长轴。
