A proteomic analysis of drought stress in barley (hordeum vulgare)
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Drought is a major threat to world agriculture. In order to identify proteins associated with plant drought tolerance, barley varieties bred in the UK (Golden Promise) and Iraq (Basrah) were compared. The variety Basrah showed physiological adaptations to drought when compared to Golden Promise, for example relative water content after one week of drought was much higher for Basrah than for Golden Promise in the leaves as well as the roots. Also the water loss rate was significantly different between the two varieties, with the Basrah variety loosing water at about half the rate of Golden Promise. DIGE analyses were carried out on proteins from roots and leaves under control and drought conditions. 24 leaf and 45 root proteins were identified by MALDI-TOF MS spectrometry. The relative expression patterns of the identified proteins fell into a number of distinct classes. The variety Basrah is characterised by constitutive expression or higher drought-induced expression levels of proteins regulating ROS production and protein folding. Photosynthetic enzymes, by contrast, were downregulated in Basrah. Enzyme assays showed a good correlation between DIGE-derived protein abundance estimates and enzyme activity in extracts. Overall this study shows that the enhanced drought tolerance of variety Basrah is driven by an enhanced regulation of ROS under drought. A number of transcription factors with enhanced expression in Basrah under drought conditions were also identified; it is hypothesised that these may contribute to the drought tolerant phenotype and thus make interesting targets for barley breeding experiments.