Differential proteomics in contrasting cowpea genotypes submitted to different water regimes
Cowpea (Vigna unguiculata) is of great importance for human consumption due to its high nutritional value. The crop is grown in tropical and subtropical regions of the world; however, grain productivity is severely affected by water restriction imposed by long periods of drought in semiarid regions. We compared two contrasting cowpea genotypes for drought tolerance through proteomic analyses by identifying differentially expressed proteins responsive to water deficit and associating them with physiological responses. Water stress-tolerant (Pingo de Ouro 1,2) and sensitive (Santo Inácio) cowpea genotypes were submitted to moderate (Ypd = -1.0 MPa) and severe (Ypd = -1.5 MPa) water deficit conditions, re-irrigation after severe water deficit, and a full irrigation regime as a control. Physiological responses and expressed proteins in response to water stress were assessed. Pingo de Ouro 1,2 showed drought tolerance by delaying dehydration, being efficient in stomatal control, increasing photosynthesis and reducing transpiration rates. Based on proteomic analysis, 108 differentially expressed proteins were identified that may be associated with drought response in both tolerant and sensitive genotypes. Drought stress-response peptides, including glutamine synthetase, CPN60-2 chaperonin, malate dehydrogenase, heat-shock proteins, and rubisco were expressed differentially in both genotypes. The changes in the proteome in cowpea leaves in response to drought can help us understand the mechanisms and specific metabolic pathways involved in drought tolerant and drought sensitive cowpea genotypes.