Effects Of Enhanced UV-B Radiation On Root Tip Quiescent Center Of Arabidopsis Thaliana

Enhanced UV-B(Ultraviolet-B,UV-B)radiation has many effects on surface organisms,especially plants.In this process,UV-B is not only a potential stress factor,but also can be used as a signal to participate in the growth and development of plants.Plant root tip stem cells can differentiate into a variety of cell types through asymmetric cell division,which is the cell source and signal regulation center of plant root development,and plays an important role in plant root development.Arabidopsis microtubule binding protein MAP18(Microtubule-associatedproteins18,MAP18)is highly expressed in roots.As a microtubule destabilizing protein,MAP18 can participate in plant growth and development by binding microtubules,including plant morphogenesis and stress.In this study,wild-type Arabidopsis thaliana(Columbia,Col-0),wild-type Arabidopsis thaliana transformed with pWOX5 promoter GFP(plants expressing green fluorescent protein driven by WOX5 promoter),Arabidopsis thaliana MAP18 gene overexpression line OE,silencing inhibition RNAi and T-DNA insertion mutant map18 were used as materials to observe the morphological changes between Arabidopsis mutant and wild type before and after radiation.The changes of green fluorescence of root tip stem cells were observed by laser confocal microscope.Biological analysis was carried out to explore the role of root tip stem cells in UV-B response,in an attempt to explain the role of MAP18 in Arabidopsis thaliana in response to UV-B stress,so as to provide clues for improving plant response to UV-B stress.The main results of this experiment are as follows:The fluorescence signal of root tip rest center(Quiescent center,QC)of wild type of Arabidopsis thaliana transformed into pWOX5 :: GFP changed after UV-B radiation.After7-day-old Arabidopsis thaliana pWOX5 :: GFP seedlings were irradiated by UV-B,the green fluorescence of WOX cells GFP representing QC cells decreased significantly at 6hours after UV-B radiation,and the green fluorescence of most seedlings disappeared completely at 24 hours after UV-B radiation.It is suggested that enhanced UV-B radiation will lead to the inactivation of QC cells in the root regulatory center,so it can be inferred that the growth of primary taproots of Arabidopsis thaliana seedlings exposed to UV-B radiation is irreversible and will not resume growth.Phenotypic analysis of Arabidopsis MAP18 overexpression strain OE,silencing inhibition RNAi and T-DNA insertion mutants by enhanced UV-B radiation.After7-day-old Arabidopsis mutants and wild-type Arabidopsis thaliana were irradiated by UV-B and returned to normal conditions for 14 days,the seedlings treated with RNAi and T-DNA insertion mutant map18 showed obvious yellowing,the yellowing degree of wild-type seedlings was slightly lighter,and the seedlings of OE,a strain overexpressing MAP18,showed the least sensitivity,and the difference was obvious.The growth of primary roots was stagnant,and the phenotype of developed lateral roots stopped growing after radiation,which verified the previous presumption.however,the wild type seedlings and MAP18 overexpression line OE seedlings recovered from UV-B radiation regenerated new fixed roots at the junction of Hypocotyl and root,that is,the transition zone,and continued to grow instead of damaged primary main roots.The number of regenerated rooting of OE seedlings of MAP18 overexpression strain was more than that of wild type,but there was almost no new rooting in the seedlings of silencing inhibition of RNAi and T-DNA insertion into mutant map18.It can be inferred that MAP18 may play a positive regulatory role under UV-B radiation treatment.Detection of QC cells in Arabidopsis thaliana seedling regeneration and rooting by enhanced UV-B radiation.When 7-day-old and 5-day-old pWOX5 seedlings of Arabidopsis thaliana were irradiated with the same dose of UV-B,it was clearly observed that the green fluorescence of WOX leaves GFP representing QC appeared at the junction between hypocotyls and roots of Arabidopsis thaliana seedlings,and then regenerated roots developed.The results showed that QC activity expression preceded root regeneration in Arabidopsis thaliana after UV-B radiation,and QC was the regulatory center of root regeneration in Arabidopsis thaliana,while QC fluorescence appeared late in 5-day-old seedlings with low MAP18 expression,and QC fluorescence appeared early in 7-day-old seedlings with high MAP18 expression.It is speculated that the activity of QC is related to the expression of MAP18.In this study,it was found that enhanced UV-B radiation damaged the resting center cells of Arabidopsis thaliana root system,resulting in irreversible damage to the main root,and MAP18 was involved in the process of root regeneration in Arabidopsis thaliana in response to UV-B injury.