The Role Of Microtubule-associated Protein AtMAP18 In Arabidopsis Thaliana Under Exogenous ABA Treatments

Abscisic acid is one of important plant hormones,it is involved in the various stages of plant growth and development.As a"hormone stress",ABA plays a key role in plant response to various stressors.Therefore,it is very important to study the mechanism of plant ABA treatments.The dynamic changes of microtubule cytoskeleton play a significant physiological function in many cell activities.Many studies have shown that the dynamic changes of microtubules are involved in ABA signal transduction pathway.Microtubule protein is the main factor of the dynamic change of microtubules,however,the study on the effect of plant adaptation to ABA stress in Arabidopsis has not been reported.AtMAP18 is a kind of microtubule-associated proteins and inhibits microtubule polymerization.In this research,wild type plants(WT),AtMAP18 overexpression(AtMAP18-OE),mutant(map18)and AtMAP18-RNAi plants are used.Under ABA treatments,we analysis the expression pattern of AtMAP18,observe the plant phenotype and the dynamic change of microtubule,and examine the expression of ABA response genes to illuminate the function of AtMAP18 under ABA treatment.The main results were as follows:1.Under exogenous ABA treatments,the expression of AtMAP18 increase significantly in gene level and protein level.2.Under normal conditions,the germination rate of AtMAP18-OE,AtMAP18-RNAi and map 18 are consistent with WT.With the increase of exogenous ABA treatments concentration,the difference of germination rate of AtMAP18-RNAi,map18 and WT increased gradually,and all plants are more serious inhibited.the germination rate of AtMAP18-OE is consistent with WT.The inhibition of AtMAP18-OE germination rate is less than AtMAP18-RNAi and mapl8.3.Under normal conditions,except for the lateral root number of AtMAP18-RNAi is slightly lower than WT,the plant of AtMAP18-RNAi,map18 and AtMAP18-OE are not significantly different from WT in leaves,leaf area,main root length and lateral root number.Under exogenous ABA treatment,the growth of AtMAP18-OE was better than that of WT,which shows that the leaf area become larger,the main root length longer and the lateral root number increase.On the contrary,the AtMAP18-RNAi and map18 leaf number is less,leaf area is smaller,root length is shorter and lateral root number is less than WT.4.Under exogenous ABA treatments,compared with the WT,the expression of ABF2,ABI3,KIN2 and RD29A in AtMAP18-OE is increased,the expression level of these genes is lower in map18 and AtMAP18-RNAi.5.Under exogenous ABA treatments,compared with the map18,the microtubule depolymerization of the WT is more obvious in the cotyledon.Whereas,the microtubule of map18 is relatively stable.In conclusion,ABA can induce the expression of AtMAP18,and AtMAP18 can regulate the dynamic changes of microtubule.Under exogenous ABA treatment,the overexpression of AtMAP18 can induce the expression of ABA response genes,which can promote the plant growth and improve the ability of the plants to adapt to ABA treatment,Contrarily,the deletion of AtMAP18 can't induce the expression of ABA response genes,inhibit plant growth and reduce the adaption ability to ABA in Arabidopsis thaliana.Therefore,the results showt that the microtubule-associated protein AtMAP18 participate in ABA signaling pathway and play a signaficant role in plant adaption to the process of ABA signal pathway in Arabidopsis thaliana.