Molecular basis of tolerance to abiotic stress in Phaseolus sp.

Water stress is the cause of important damage to plants at the cellular level, and responsible for substantial yield loss throughout the world. Research on the physiological and biochemical basis of the plant"s response is necessary for understanding plant growth and development, and for crop improvement. The aim of this project is to study the response of several bean species and common bean cultivars with different sensitivities to drought and flooding, in order to evaluate the molecular basis of greater resistance to stress. On the basis of monitoring several physiological parameters, appropriate plants will be selected. Analysis of their gene expression by differential display RT-PCR and quantitative real-time PCR will be carried out. In order to follow a large number of genes at a time a DNA microarrays methodology will be initiated. Differentially expressed genes in leaves of drought stressed and control plants will be analysed. Their expression in different cultivars and under flooding stress will be determined. Additionally, changes in activity of proteolytical enzymes affecting selective or uncontrolled protein breakdown will be studied. The scanning procedure developed in our laboratory will be used to identify the proteases and/or their endogenous inhibitors, and to assign individual proteases to an identified change in activity under stress. The activities of proteases in control and stressed plants with different sensitivities will then be compared on a quantitative basis. Selected protease(s) will be characterised, in order to perform cDNA cloning and expression analysis. The proposed investigation will contribute to a deeper understanding of the mechanism of plant response to drought and flooding and, ultimately, to improving resistance in Phaseolus cultivars. It will also enable us to join international efforts already initiated to improve the quality and yield of common bean.