Gene expression changes in response to combination stresses in Phaseolus vulgaris L. (Fabaceae)

Plants are continuously exposed to a broad range of environmental stresses. Common bean (Phaseolus vulgaris L.) is found to be seventh major world food crop widely attacked by several pests including a generalist herbivore, Tetranychus urticae Koch. We investigated the transcriptome signature of some genes (two Pathogen Related Protein (PR3 and PR4), phenylalanine ammonia-lyase (PAL), Lipoxygenase (LOX), phenylalanine ammonia-lyase (PAL) and (E)-β-ocimene synthase (OS)) in four common bean accessions which have been previously recognized to be resistant to Tetranychus urticae (two varieties with the highest degree of resistance, i.e. Naz and Ks41128, and the two varieties with the lowest degree of resistance, Akthar and G11867) in response to single stress (only T. urticae infestation) versa dual stress combinations (moderate drought stress and T. urticae infestation). Drought pretreatment significantly modified the transcriptome signature of some Phaseolus vulgaris varieties infested with T. urticae. The obtained results addressed for the impact of combined stresses at the transcriptome level, with some gene expression (PAL in Naz, Akhtar, LOX in Naz and Akhtar, PR4 in Akhtar and Ks41128, PR3 in Ks41128 and OS in Ks41128 and G11867) increasing after multiple stresses but not after single stress. Drought stress could alter the gene expression pattern in genotypes regardless of their resistibility/susceptibility to the spotted spider mite. Collectively, the results highlight the complex nature of multiple stress responses and that common bean varieties responses to multiple stresses are complicated as well as unpredictable.