Cloning and characterization of ChiMYB in Chrysanthemum indicum with an emphasis on salinity stress tolerance

v-myb avianmyeloblastosis viral oncogene homolog (MYB) transcription factors are key regulators of stress responsive gene expression in plants. In this study, the MYB gene, ChiMYB (GenBank accession No. KT948997), was isolated from Chrysanthemum indicum, and was functionally characterized with an emphasis on salinity stress tolerance. The full ChiMYB cDNA sequence (948 bp) encoded a typical R2R3 MYB transcription factor that contained 315 amino acid residues and two MYB domains. The temporal expression pattern of ChiMYB was noted in C. indicum, and the highest level was detected in the roots, followed by leaves and stems. ChiMYB expression was induced by NaCl treatments, and transient expression of the fusion of ChiMYB and green fluorescent protein (GFP) indicated that the protein was targeted to the nuclei of onion epidermal cells. Arabidopsis plants overexpressing ChiMYB displayed improved tolerance to drought and salt stress. When under salt stress conditions, transgenic Arabidopsis plants had higher survival rates than non-transgenic wild-type plants. Chlorophyll content, intercellular CO₂ concentration, photosynthetic rate, and stomatal conductance were higher in the transgenic Arabidopsis plants than in non-transgenic control plants. Further investigation revealed that ChiMYB was able to regulate the expression of RD29A, RAB18, COR15, ABI1, and ABA genes, which are involved in salt stress signaling pathways. Our findings demonstrated that ChiMYB is essential for plant responses to salt stress, and it may have great potential for the improvement of salt tolerance in crops.