Identification of genes involved in the response of leaves of Phaseolus vulgaris to drought stress

Common bean (Phaseolus vulgaris L.) is an important crop from the Fabaceae family that is cultivated worldwide for human consumption. It is also widely exposed to drought. The identification of genes whose expression is altered under conditions of drought is an important first step towards understanding the response of this species. Such a study has recently been published on roots of P. vulgaris (Torres et al. 2006, Plant Sci 171:300-307) and a complementary study is here reported on leaves. 19-day-old plants of 8 cultivars grown in a growth chamber and 21-day-old plants of four of these cultivars grown in a greenhouse under conditions nearer to those in the field, were subjected to progressive water withdrawal. Changes in gene expression in their leaves at different levels of dehydration were identified by differential display reverse transcriptase PCR and confirmed by quantitative real-time PCR. The levels of 15 transcripts were changed significantly (P < 0.05) in all cultivars under both growth conditions, 8 being increased and seven decreased. All these transcripts were related by blastp search to known plant proteins. At least six transcripts corresponded to those whose expression is altered under drought in Arabidopsis thaliana. Five of the genes identified have not previously been reported as being influenced by drought. The identified genes were different from those influenced by drought in roots of P. vulgaris. Only minor differences in expression of these 15 genes were found between the different cultivars.