The Role Of Microtubule-associated Proteins AtMAP18 In Arabidopsis Thaliana Under Exogenous SA Treatments

Salicylic Acid(SA)is a important phytohormone,as stress reponse pytohormone,it involves in many processes of plant growth and developmentand plays vital roles in response to biotic and abiotic stressTherefore,it is important for understanding the mechanism of plant response to SA signal transduction pathway.The dynamic of microtubules plays an important role in many cell activities,and microtubule regulatory proteins regulate the organization and dynamics of microtubules.It has been reported that AtMAP18 is a microtubule destabilizing proteinand the expression of AtMAP18 is induced by SA treatment.however,it is unknown whether AtMAP18 is involved in plant response to SA signaling pathway and how it functions.In this study,we examined the expression pattern of AtMAP18 treatment by SA.The seed germination,plant growth and the organization and dynamics of microtubules in wild type plants(WT),AtMAP18 overexpression(AtMAP18-OE),mutant(Atmap18)and AtMAP18-RNAi seedlings were analyzed with or without SA treatment.In addition,the expression levels of SA response genes were detected in WT and Atmap18 treated with or without SA.The main results were as follows:1.Under exogenous SA treatments,the expression of AtMAP18 increased significantly in gene level and protein level.2.Under normal condition,the seed germination rate of WT,AtMAP18-OE,Atmap18 and AtMAP18-RNAi had no significant difference.However,under exogenous SA treatment,the germination rate were suppressed in these plants,compared with WT,the germination rate of AtMAP18-OEwas higher while Atmap18 and AtMAP18-RNAi was lower,illustrate AtMAP18 plays a positive role in the seed germination under SA treatment.3.Under normal conditions,there was no significant difference in the main root length and leaf area of WT,AtMAP18-OE,Atmap18 and AtMAP18-RNAi plants.Under exogenous SA treatment,the main root length and leaf area of the four plants decreased significantly,and the growth was inhibited.The leaf area and main root length of AtMAP18-OE plants were significantly higher than that of WT under the treatment of 0.05 mM SA,while the leaf area and main root length of Atmap18 and AtMAP18-RNAi plants were significantly lower than that of WT.Itsuggested that the overexpression of AtMAP18 was beneficial to the growth of Arabidopsis,whereas the absence of AtMAP18 was not conducive to the growth of Arabidopsis plants.4.Under exogenous SA treatment,compared with the WT plants,the corticalmicrotubules in Atmap18 cotyledonpavement cell were insensitive to microtbule destabilizing drug oryzalin,suggesting that the microtubules in Atmap18 were more stable than that of WT.5.Under exogenous SA treatment,the expression of PR1,PR2,PR5 gene in AtMAP18-OE plants was significantly higher while Atmap18 and AtMAP18-RNAi plants was lower than that of WT plants.Under exogenous SA treatment,AtMAP18 positively regulate PR1,PR2,PR5 gene expression,suggesting that AtMAP18 may be involved in SA signaling pathway by regulation the PR1,PR2,PR5 gene expression in Arabidopsis.In conclusion,AtMAP18 is positively involved in Arabidopsis SA signaling pathway by regulating microtubule dynamic and PR1,PR2 and PR5 gene expression.