The R2R3-MYB transcription factor AtMYB49 modulates salt tolerance in Arabidopsis by modulating the cuticle formation and antioxidant defence

Salt stress activates defence responses in plants, including changes in leaf surface structure. Here, we showed that the transcriptional activation of cutin deposition and antioxidant defence by the R2R3-type MYB transcription factor AtMYB49 contributed to salt tolerance inArabidopsis thaliana. Characterization of loss-of-functionmyb49mutants, and chimericAtMYB49-SRDX-overexpressingSRDX49transcriptional repressor andAtMYB49-overexpressing (OX49) overexpressor plants demonstrated a positive role ofAtMYB49in salt tolerance. Transcriptome analysis revealed that many genes belonging to the category cutin, suberin and wax biosyntheses were markedly up-regulated and down-regulated inOX49andSRDX49plants, respectively, under normal and/or salt stress conditions. Some of these differentially expressed genes, includingMYB41,ASFT,FACTandCYP86B1, were also shown to be the direct targets of AtMYB49 and activated by AtMYB49. Biochemical analysis indicated that AtMYB49 modulated cutin deposition in the leaves. Importantly, cuticular transpiration, chlorophyll leaching and toluidine blue-staining assays revealed a link between increased AtMYB49-mediated cutin deposition in leaves and enhanced salt tolerance. Additionally, increasedAtMYB49expression elevated Ca(2+)level in leaves and improved antioxidant capacity by up-regulating genes encoding peroxidases and late embryogenesis abundant proteins. These results suggest that genetic manipulation ofAtMYB49may provide a novel way to improve salt tolerance in plants.