Roles Of Pectin Methylesterase In Brassinosteroid Regulations Of Growth And Development In Arabidopsis

Pectin,whose structures and functions are closely related to its esteration status,is one of the main components of plant cell wall.Pectin esteration is regulated by pectin methylesterase(PME)which demethylesterfies pectin to pectic acid and methanol,and is regulated by pectin methylesterase inhibitor(PMEI).It's reported that BR signals regulate cell wall homeostasis and in turn was regulated by pectin modification.BRs play important roles in plant growth and development;however,its unclear about the functions and mechanisms of cell wall pectin methylesteration in BR-related plant development.In this thesis,we studied the roles of PME41 and PMEI7 in BR regulation of Arabidopsis growth and development.The main results are as follows.1 Constructed 35S::PME41 expression vector and transformed it into Col-0 wild type,with artificial hybridization,we got hybrid plants oxPME41/det2 and pme41/det2,and the PME activity were analyzed in different genotype.The results indicate that compared with non-transgenic plant,PME activity was higher in oxPME41 and oxPME41/det2,implying that PME41 has PME activity,however,compared with Col-0 wild type,PME activity had no obvious changes in BR synthetic-deficit mutant det2,pme41 mutant and pme41/det2,implying that PME41 had no evident contribution to the tissue whole PME.2.Constructed PME41-pro::GUS expression vector and transformed it into Col-0 wild type,observed GUS localization in different development stages.The results indicated that in 12 days seeding,GUS was mainly expressed in cotyledon,euphylla,root maturation zone and elongation zone,but hardly expressed in hypocotyl,petiole root cap and meristematic zone.In flowering period,GUS was expressed in sepal and style,but hardly expressed in petal,anther and stigma.Furthermore,GUS stain in filament showed increasing in floral stage 13 and stage 14.These results indicating PME41 was expressed varies in different tissue,and probably function in filament elongation.3 Constructed 35S::PMEI7 expression vector and transformed it into Col-0 wild type,with artificial hybridization,we got hybrid plants oxPMEI7/det2 and the PME activity were analyzed in transgenic plant.The results indicate that PME activity was lower in oxPMEI7 while it changed a little in oxPMEI7/det2,implying that PMEI7 has PMEI activity,but its inhibitory function might relevant to BR4 Analyzed the effect on root growth in PME41 and PMEI7,and the result showed that Compared with Col-0 wild type,det2 restrained root growth with significantly shorten roots,but the roots length were similar in pme41 mutant,oxPME41 and oxPMEI7 with Col-0.Most interestingly,the root length in pme41/det2?oxPME41/det2 and oxPMEI7/det2 was much longer than in det2 mutant,partially restored growth defects phenotype in det2.Preliminary analyzed det2 root recovery mechanism in PME41 and PMEI7,elongation cells in pme41/det2,oxPME41/det2 and oxPMEI7/det2 were also much longer than det2,thus further influenced root elongation.this might the main cause for root elongation.5.Analyzed the effect on plant development in PME41 and PMEI7,compared with det2,pme41/det2?oxPME41/det2 and oxPMEI7/det2 appeared bigger rosettes,more inflorescence branches,smaller siliques,larger size but less numbers in seeds.Further explored det2 fertility mechanism in PME41 and PMEI7,discovered that pollen grain activity and pollen length altered nothing in pme41 mutant,oxPME41 and oxPMEI7,but the filament length statistic showed shortened filament in pme41/det2,oxPME41/det2 and oxPMEI7/det2 than in det2,this might a main cause for siliques size changes in Arabidopsis.6 qPCR analysis also suggested that BR synthesis genes DET2,CPD,DWF4 were down-regulated in pme41,oxPME41 and oxPMEI7 with different degrees,in turn,some other PME and PMEI genes were up-regulated in different BR mutant det2,bri1-116,dwf4,indicating a close relationship between cell wall pectin modification genes and BR synthesis genes.Compared with det2,expression of growth relate genes PRE1 and SAUR-AC1 were all down-regulated in pme41/det2,oxPME41/det2 and oxPMEI7/det2,of which keeps a certain balance condition.All the results above revealed a complex relation in BR and pectin methylesterase of which offered more possibility in Arabidopsis growth and development.