Transcriptomic Profiling Of Melatonin And Auxin Treated Arabidopsis And Systematic Analysis Of The 14-3-3 Gene Family In Arabidopsis And Brachypodium Distachyon

Melatonin is a ubiquitous molecule and exists across kingdoms including plant species.Numerous studies have shown that melatonin is widely involved in regulating biotic and abiotic stress tolerances,biological rhythms,plant growth and development(seed germination,root architecture,shoot development,plant flowering,fruit ripening,and yield).Melatonin promotes root growth at low concentration and inhibits root growth at high concentration.It's reported that melatonin and IAA share the same substrate(tryptophan)during the biosynthesis.Therefore,melatonin might have similar function with IAA.In this study,we analyzed transcriptomic changes of Arabidopsis in response to low concentration of melatonin at 10-8M and indole-3-acetic acid(IAA)at 10-10M,respectively.The results showed that the majority of genes modulated by melatonin and IAA are the same.Pathway and GO term enrichment analyses showed that many pathways were consistently modulated by both melatonin and IAA at low concentration.Further studies showed that melatonin improved root growth in WT,but not in yucQ mutant.Moreover,when WT pretreated with high concentration of IAA inhibitors L-AOPP(IAA biosynthesis inhibitor)and TIBA(IAA transport inhibitor),melatonin is not able to improve root growth.These results indicated that the effect of improved root growth by low concentration of melatonin is dependent on the presence of IAA.We further characterized transcriptomic changes after treatments with high concentration melatonin(1 00?M,1 000?M).Pathways including fermentation,secondary metabolism,hormone metabolism and amino acid metabolism were highly enriched,indicating these pathways might be involved in high concentration melatonin inhibiting root growth.Several 14-3-3 genes were modulated by melatonin in RNA seq data.We created 14-3-3 overexpression lines and RNAi lines in Arabidopsis.The results showed that 14-3-3 RNAi lines is sensitive to ABA and drought stress treatment,while 14-3-3 overexpression lines were tolerant to ABA and drought,indicating Arabidopsis 14-3-3 genes might function as positive regulator during plant in response to ABA and drought stress.We further analyzed 14-3-3 family genes in Brachypodium distachyon and obtained BdGF14a gene overexpressed transgenic lines in Arabidopsis.In total seven B.distachyon 14-3-3 genes were identified.Results of gene expression analysis showed that these genes were induced by abiotic stresses or hormone treatments.Transgenic Arabidopsis overexpressing BdGF14a exhibited increased leaf water content(LWC)and decreased electrolyte leakage(EL)and showed improved drought stress tolerance.BdGF14a transgene significantly up-regulated expression levels of DREB1A and DREB1B,but slightly elevated ABI1 expression.These results indicated that BdGF14a functioned as a positive regulator in plant response to drought stress mainly via ABA independent pathway.