Molecular Plant ( IF 27.5 ) Pub Date : 2020-09-08 , DOI: 10.1016/j.molp.2020.09.004 Yiming Shao 1 , Xinxing Yu 1 , Xuwen Xu 1 , Yong Li 1 , Wenxin Yuan 1 , Yan Xu 1 , Chuanzao Mao 1 , Shuqun Zhang 2 , Juan Xu 1
The mitotic activity of root apical meristem (RAM) is critical to primary root growth and development. Previous studies have identified the roles of ROOT GROWTH FACTOR 1 (RGF1), a peptide ligand, and its receptors, RGF1 INSENSITIVEs (RGIs), a clade of five leucine-rich-repeat receptor-like kinases, in promoting cell division in the RAM, which determines the primary root length. However, the downstream signaling components remain elusive. In this study, we identify a complete mitogen-activated protein kinase (MAPK or MPK) cascade, composed of YDA, MKK4/MKK5, and MPK3/MPK6, that functions downstream of the RGF1-RGI ligand–receptor pair. Similar to the rgi1/2/3/4/5 quintuple mutant, loss-of-function mutants of MPK3 and MPK6, MKK4 and MKK5, or YDA show a short-root phenotype, which is associated with reduced mitotic activity and lower expression of PLETHORA 1 (PLT1)/PLT2 in the RAM. Furthermore, MPK3/MPK6 activation in response to exogenous RGF1 treatment is impaired in the rgi1/2/3/4/5 quintuple, yda single, and mkk4 mkk5 double mutants. Epistatic analyses demonstrated that the expression of constitutively active MKK4, MKK5, or YDA driven by the RGI2 promoter can rescue the short-root phenotype of the rgi1/2/3/4/5 mutant. Taken together, these results suggest that the YDA-MKK4/MKK5-MPK3/MPK6 cascade functions downstream of the RGF1-RGI ligand–receptor pair and upstream of PLT1/PLT2 to modulate the stem cell population and primary root growth in Arabidopsis.
中文翻译:
YDA-MKK4 / MKK5-MPK3 / MPK6级联作用在RGF1-RGI配体-受体对的下游调节根尖分生组织的有丝分裂活性。
根尖分生组织(RAM)的有丝分裂活性对于初级根的生长和发育至关重要。先前的研究已经确定了根系生长因子1(RGF1),一种肽配体及其受体,RGF1 INSENSITIVEs(RGI),五个富含亮氨酸的重复受体样激酶的进化枝在促进RAM中的细胞分裂中的作用,它确定主根长度。但是,下游信令组件仍然难以捉摸。在这项研究中,我们确定了由YDA,MKK4 / MKK5和MPK3 / MPK6组成的完整的促丝裂原活化蛋白激酶(MAPK或MPK)级联,其在RGF1-RGI配体-受体对的下游起作用。类似于rgi1 / 2/3/4/5的五元组突变体,的失功能突变体MPK3和MPK6,MKK4和MKK5或YDA显示出短根表型,这与有丝分裂活性降低和RAM中PLETHORA 1(PLT1)/ PLT2的表达降低有关。此外,在rgi1 / 2/3/4/5五倍体,yda单和mkk4 mkk5双突变体中,响应外源RGF1处理的MPK3 / MPK6激活受到损害。上位性分析表明,由RGI2启动子驱动的组成性活性MKK4,MKK5或YDA的表达可以挽救rgi1 / 2/3/4/5的短根表型突变体。综上所述,这些结果表明,YDA-MKK4 / MKK5-MPK3 / MPK6级联在RGF1-RGI配体-受体对的下游和PLT1 / PLT2的上游起作用,以调节拟南芥中的干细胞种群和初生根生长。