Ectopic expression of a wheat MYB transcription factor gene, TaMYB73, improves salinity stress tolerance in Arabidopsis thaliana

MYB transcription factors (TFs) play pivotal roles in the abiotic stress response in plants, but their characteristics and functions in wheat (Triticum aestivum L.) have not been fully investigated. A novel wheat MYB TF gene, TaMYB73, is reported here based on the observation that its targeting probe showed the highest salinity-inducibility level among all probes annotated as MYB TFs in the cDNA microarray. TaMYB73 is a R2R3 type MYB protein with transactivation activity, and binds with types I, II, and IIG MYB binding motifs. The gene was induced by NaCl, dehydration, and several phytohormones, as well as some stress-, ABA-, and GA-responsive cis-elements present in its promoter region. Its over-expression in Arabidopsis enhanced the tolerance to NaCl as well as to LiCl and KCl, whereas it had no contribution to mannitol tolerance. The over-expression lines had superior germination ability under NaCl and ABA treatments. The expression of many stress signalling genes such as AtCBF3 and AtABF3, as well as downstream responsive genes such as AtRD29A and AtRD29B, was improved in these over-expression lines, and TaMYB73 can bind with promoter sequences of AtCBF3 and AtABF3. Taken together, it is suggested that TaMYB73, a novel MYB transcription factor gene, participates in salinity tolerance based on improved ionic resistance partly via the regulation of stress-responsive genes.