Differentially Expressed Genes during Flowering and Grain Filling in Common Bean (Phaseolus vulgaris) Grown under Drought Stress Conditions

Drought stress, particularly during the flowering and grain-filling stages of growth, contributes to serious yield loss in common bean (Phaseolus vulgaris L.). The aim of this study was to identify genes induced in response to drought stress using transcriptome analysis of contrasting genotypes. Using leaf tissues of tolerant (BAT 477) and susceptible common bean genotypes (P,rola), collected at the flowering and grain-filling stages, four complementary deoxyribonucleic acid representational difference analysis subtractive libraries were constructed and then sequenced. A total of 7,203 (77.6 %) sequences with an average sequence size of 570 bp were considered valid, for a combined 4 Mbp sequence. According to a differential display analysis, 802 expressed sequence tags, distributed across 67 contigs, were differentially expressed by the tolerant (37 contigs) and susceptible genotypes (30 contigs) after identification under drought conditions during the two investigated plant developmental stages. Of these differential contigs, the 13 most frequent genes were exclusive to the tolerant genotype. Based on BLAST2GO, 73 % of the gene sequences were annotated and 12 % showed mapping results, with the highest similarity rate corresponding to Glycine max (41 %). According to gene ontology functional analysis, 48 % of the sequences were attributed to cell metabolic processes. Overall, 8.3 % of the transcribed sequences exhibited similarity to transcription factors, predominantly those of the AP2-EREBP family (97.8 %). Of the target sequences validated by quantitative real-time polymerase chain reaction, most genes showed an expression level that agreed with that predicted by in silico analysis. Thus, the drought transcriptome dataset is a valuable resource on the variation in these gene sequences, offering the opportunity to identify robust molecular markers tightly linked to trait-controlling loci for use in marker-assisted breeding.