Comparative transcript profiling in roots of Phaseolus acutifolius and P. vulgaris under water deficit stress

Transcript profiles in roots of Phaseolus acutifolius and P. vulgaris were compared under water deficit conditions that demonstrated the drought resistance phenotype of P. acutifolius. Differential gene expression was monitored with microarray analysis using slides printed with ∼5200 anonymous cDNAs from libraries of Phaseolus spp. Those genes whose expression was significantly altered by water deficit were sequenced and functional classifications were inferred based on similarity to other annotated genes. Fewer genes (n = 64) were responsive in P. vulgaris, the more drought sensitive species, compared with P. acutifolius (n = 488). Only 25 genes were drought responsive in the roots of both species, at a drought stress level of −2.5 MPa leaf water potential. Most of the responsive genes in P. vulgaris were in the functional class for stress responsive genes, while the largest functional class in P. acutifolius was populated with unannotated or novel genes. There were a number of genes likely to be important in cell growth and metabolism that were uniquely stress responsive in P. acutifolius.