Receptor-Like Kinase TMKs Regulate The Development Of Root Tip In Arabidopsis Thaliana

Root can adjust its pattern of growth and development in response to environmental cues.This characteristic can be conferred by stem cells in the root apical meristem.In the process of the development of root apical meristem,QC is crucial for the formation of the stem cell niche which is regulated by many factors.Auxin and cytokinin interact antagonistically to control the size of root apical meristem.PLTs and SHR/SCR are important for the maintenance of QC specification and stem cell identify.Recent studies show that TMKs are involved in the regulation of lateral root organogenesis,inhibition of cell elongation by auxin during hypocotyl apical hook formation,and gravitropism.TMKs also regulate root meristem development by affecting the tryptophan-dependent auxin synthesis pathway.These results indicate that TMKs are important for the growth and development of Arabidopsis thaliana.However,there is little experimental evidence on the regulation of root apical meristem by TMKs.In order to study the mechanism that TMKs regulate root tip development,this study mainly use cell biology methods to preliminarily explore the function of TMKs in the regulation of the root apical meristem development.The detailed results are as follows:(1)Genetic phenotypic analysis showed that loss of function of TMKs reduced the length of meristem and resulted in a decrease in the number of meristematic cells of the root tip,suggesting that TMKs functionally deficient mutations affected the activity of stem cell niche.(2)Studies of cell biology showed that loss of function of TMKs reduced auxin accumulation in root tip.And the expressions of auxin efflux transporters PIN3 and PIN7 significantly decreased in the mutant background,suggesting that the effect of TMKs mutant on the root tip development may be exerted through the Auxin-PLTs pathway.Further cell biology and molecular biology experimental results showed that loss of function of TMKs influenced the expressions of PLT1 and PLT2 at transcriptional level and translational level,respectively.These results further suggested that the functions of TMKs family members were not completely redundancy.(3)Studies of cell biology showed that TMKs functionally deficient mutations significantly reduced the expressions of SHR and SCR,but there was no obvious defect in the radial patterning of tmk1,3,4 mutant.The biological function of the decreased expression of SHR and SCR remains to be further studied.(4)The results of laser confocal microscopy showed that loss-of-TMKs mutant significantly reduced the expression of QC25 but had no effect on the transcriptional activity of WOX5.The results of m PS-PI and Lugo's staining further indicated that loss of function of TMKs had no effect on the distal meristem.(5)Cell biology studies showed that loss-of-TMKs mutant enhanced the expression of ARR1 and reduced the expression of ARR5,indicated that the activity of cytokinin signal transduction was enhanced in tmk1,3,4 mutant background.Further studies showed that loss of function of TMKs affected cell mitotic activity.Combined with above experimental results,the following conclusions can be drawn: TMKs may be involved in the regulation of cytokinin signal transduction,affecting the polar transport of auxin,thereby changing the accumulation of auxin in the root tip,and reducing the mitotic activity of meristematic cells.This study provides a new sight on the regulation of Plant root tip development by TMKs and has an important scientific significance for further research on the mechanism of action of TMKs.