The barley transcription factor HvMYB1 is a positive regulator of drought tolerance

Transcription factors such as MYB have previously been associated with the plant response to drought. In this work, studies on the function of the barley (Hordeum vulgare L.) transcription factor HvMYB1 show that gene expression is upregulated in wildtype barley roots and leaves under drought and osmotic stress. Transgenic barley plants that overexpress HvMYB1 were found to be more resistant to drought, showing enhanced relative water content and reduced water loss rate and stomatal conductance as compared to control plants. Levels of the osmolyte proline were enhanced as was expression of dehydrin HvDNH6 in the transgenic lines under drought conditions. The levels of the reactive oxygen species H₂O₂ were enhanced in wildtype roots and leaves by drought, but less so in the HvMYB1 overexpressing lines. Enzyme activity of the low affinity H₂O₂ degrading enzyme catalase (EC 1.11.1.6) was also lower in droughted HvMYB1 overexpressing lines. Gene expression of the high affinity ROS scavengers ASCORBATE PEROXIDASE and GLUTATHIONE PEROXIDASE was found to be constitutively high in the overexpressing lines, whereas CATALASE gene expression was similar to the control plants. These results suggest a role for HvMYB1 in protecting plants against drought in the vegetative plant by acting as a mediator of abscisic acid action.