Characterization of wheat MYB genes responsive to high temperatures

Heat stress is one of the most crucial environmental factors, which reduces crop yield worldwide. In plants, the MYB family is one of the largest families of transcription factors (TFs). Although some wheat stress-related MYB TFs have been characterized, their involvement in response to high-temperature stress has not been properly studied.

Six novel heat-induced MYB genes were identified by comparison with previously established de novo transcriptome sequencing data obtained from wheat plants subjected to heat treatment; genomic and complete coding sequences of these genes were isolated. All six TaMYBs were localized in the nucleus of wheat protoplasts. Transactivation assays in yeast revealed that all six proteins acted as transcriptional activators, and the activation domains were attributed to the C-termini of the six wheat MYB proteins. Phylogenetic analysis of the six TaMYBs and R2R3-MYBs from Arabidopsis revealed that all six proteins were in clades that contained stress-related MYB TFs. The expression profiles of TaMYB genes were different in wheat tissues and in response to various abiotic stresses and exogenous abscisic acid treatment. In transgenic Arabidopsis plants carrying TaMYB80 driven by the CaMV 35S promoter, tolerance to heat and drought stresses increased, which could be attributed to the increased levels of cellular abscisic acid.

We identified six heat-induced MYB genes in wheat. We performed comprehensive analyses of the cloned MYB genes and their gene products, including gene structures, subcellular localization, transcriptional activation, phylogenetic relationships, and expression patterns in different wheat tissues and under various abiotic stresses. In particular, we showed that TaMYB80 conferred heat and drought tolerance in transgenic Arabidopsis. These results contribute to our understanding of the functions of heat-induced MYB genes and provide the basis for selecting the best candidates for in-depth functional studies of heat-responsive MYB genes in wheat.