Department of Botany and Laboratory of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
PLoS One. 2013 Apr 16;8(4):e60990. doi: 10.1371/journal.pone.0060990. Print 2013.
Mechanisms that govern the size of plant organs are not well understood but believed to involve both sensing and signaling at the cellular level. We have isolated loss-of-function mutations in the four genes comprising the transmembrane kinase TMK subfamily of receptor-like kinases (RLKs) in Arabidopsis. These TMKs have an extracellular leucine-rich-repeat motif, a single transmembrane region, and a cytoplasmic kinase domain. While single mutants do not display discernable phenotypes, unique double and triple mutant combinations result in a severe reduction in organ size and a substantial retardation in growth. The quadruple mutant displays even greater severity of all phenotypes and is infertile. The kinematic studies of root, hypocotyl, and stamen filament growth reveal that the TMKs specifically control cell expansion. In leaves, TMKs control both cell expansion and cell proliferation. In addition, in the tmk double mutants, roots and hypocotyls show reduced sensitivity to applied auxin, lateral root induction and activation of the auxin response reporter DR5: GUS. Thus, taken together with the structural and biochemical evidence, TMKs appear to orchestrate plant growth by regulation of both cell expansion and cell proliferation, and as a component of auxin signaling.
植物器官大小的调控机制尚不清楚，但据信涉及细胞水平的感应和信号传递。我们已经在拟南芥中分离到了组成跨膜激酶 TMK 亚家族受体样激酶 (RLKs) 的四个基因的功能丧失突变。这些 TMKs 具有细胞外富含亮氨酸重复序列基序、一个单一的跨膜区域和一个细胞质激酶结构域。虽然单个突变体没有表现出明显的表型，但独特的双和三突变体组合导致器官大小严重减小和生长显著延迟。四重突变体显示出所有表型的更严重程度，并且不育。对根、下胚轴和雄蕊花丝生长的运动学研究表明，TMKs 特异性地控制细胞扩张。在叶片中，TMKs 控制细胞扩张和细胞增殖。此外，在 tmk 双突变体中，根和下胚轴对施加的生长素的敏感性降低，侧根诱导和生长素应答报告基因 DR5:GUS 的激活减少。因此，综合结构和生化证据，TMKs 似乎通过调节细胞扩张和细胞增殖以及作为生长素信号的组成部分来协调植物生长。
