Differential Expression of Genes for Tolerance to Salt Stress in Common Bean (Phaseolus vulgaris L.)

Crop production is severely reduced by abiotic stresses such as drought, salinity, and extreme temperatures. The common bean (Phaseolus vulgaris L.) is the most important legume for direct human consumption worldwide. In order to identify genes that are induced during the salt stress response in a tolerant bean cultivar (Pinto Villa), suppression subtractive hybridization was performed. The tester cDNA was prepared from the leaves of bean plants treated with 200 mM NaCl for 2 and 5 days and the driver cDNA from the leaves of the unstressed plants. After hybridizing and cloning, forward subtraction cDNA library was obtained, and 67 unigenes were generated from 380 randomly picked clones. These unigenes were classified into ten categories according to their putative function assigned by the Gene Ontology database. Six unigenes were selected to analyze for differential expression by qRT-PCR, including heat shock proteins such as PvDnaJ3 and PvHSP90, late embryogenesis abundant proteins such as PvLEA-18 and dehydrin PvERD10, the transcription factor PvATHB-7, and a protein of unknown function that contains a short glycine-rich domain (PvGRDP1). These genes were found differentially expressed in a time-dependent manner in bean tissues under salt stress. Data generated from this study suggests that the response of the Pinto Villa bean cultivar to salt stress could be through the regulation of genes such as chaperones, transcription factors, and late embryogenesis abundant proteins which are involved in plant tolerance.