Department of Biological Sciences, Faculty of Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543.
Development. 2012 May;139(9):1568-76. doi: 10.1242/dev.079426.
Gibberellins (GA) are an important family of plant growth regulators, which are essential for many aspects of plant growth and development. In the GA signaling pathway, the action of GA is opposed by a group of DELLA family repressors, such as RGA. Although the mechanisms of action of the DELLA proteins have been studied in great detail, the effectors that act downstream of DELLA proteins and bring about GA-responsive growth and development remain largely unknown. In this study, we have characterized STUNTED (STU), a receptor-like cytoplasmic kinase (RLCK) VI family gene, which is ubiquitously detectable in all the tissues examined. RGA activity and GA signaling specifically mediate the levels of STU transcripts in shoot apices that contain actively dividing cells. stu-1 loss-of-function mutants exhibit retarded growth in many aspects of plant development. During the vegetative phase, stu-1 seedlings develop smaller leaves and shorter roots than wild-type seedlings, while during the reproductive phase, stu-1 exhibits delayed floral transition and lower fertility. The reduced stature of stu-1 partly results from a reduction in cell proliferation. Furthermore, we present evidence that STU serves as an important regulator mediating the control of cell proliferation by GA possibly through two cyclin-dependent kinase inhibitors, SIM and SMR1. Taken together, our results suggest that STU acts downstream of RGA and promotes cell proliferation in the GA pathway.
赤霉素（GA）是一类重要的植物生长调节剂，对植物生长和发育的许多方面都至关重要。在 GA 信号通路中，GA 的作用受到一组 DELLA 家族抑制剂的拮抗，如 RGA。尽管 DELLA 蛋白的作用机制已经被深入研究，但 DELLA 蛋白下游的效应子以及引起 GA 响应性生长和发育的效应子在很大程度上仍然未知。在这项研究中，我们对 STUNTED（STU）进行了表征，STU 是一种普遍存在于所有检查组织中的受体样细胞质激酶（RLCK）VI 家族基因。RGA 活性和 GA 信号特异性调节含有活跃分裂细胞的茎尖中 STU 转录本的水平。stu-1 功能丧失突变体在植物发育的许多方面表现出生长迟缓。在营养阶段，stu-1 幼苗的叶片比野生型幼苗小，根比野生型幼苗短，而在生殖阶段，stu-1 表现出延迟的花转变和较低的育性。stu-1 的矮小部分是由于细胞增殖减少所致。此外，我们提供了证据表明，STU 作为一个重要的调节剂，通过两种细胞周期蛋白依赖性激酶抑制剂 SIM 和 SMR1 介导 GA 对细胞增殖的控制。总之，我们的结果表明，STU 作为 RGA 的下游因子，在 GA 途径中促进细胞增殖。
