Transcriptomic analysis of chilling stress in Phaseolus spp.

The wild bean species Phaseolus angustissimus has shown a greater ability to survive chilling temperatures than the cultivated bean Phaseolus vulgaris. Arrays of cDNA clones from cold acclimated crowns of Medicago sativa were used to measure low temperature-induced changes in the expression profiles of both bean species and compare them to each other. Macroarray hybridization results indicate that P. vulgaris failed to sustain homeostatic expression levels of more genes than did P. angustissimus after 3 days of chilling temperature exposure. Expression patterns of selected genes were further characterized with RT-PCR using plants exposed to various durations of chilling. The most notable difference between the two species in these gene expression experiments was that P. angustissimus was able to recover the expression of a cytochrome P450 species under chilling temperature exposure whereas P. vulgaris failed to sustain levels of cytochrome P450 gene expression levels. Results of these experiments suggest that a key to chilling tolerance in Phaseolus is maintenance of homeostatic gene expression levels under chilling conditions.