Proteomic analysis of common bean stem under drought stress using in-gel stable isotope labeling

Drought is an abiotic stress that strongly influences plant growth, development and productivity. Proteome changes in the stem of the drought-tolerant common bean (Phaseolus vulgaris L.) cultivar Tiber have were when the plants were exposed to drought. Five-week-old plants were subjected to water deficit by withholding irrigation for 7, 12 and 17days, whereas control plants were regularly irrigated. Relative water content (RWC) of leaves, as an indicator of the degree of cell and tissue hydration, showed the highest statistically significant differences between control and drought-stressed plants after 17days of treatment, where RWC remained at 90% for control and declined to 45% for stressed plants. Plants exposed to drought for 17days and control plants at the same developmental stage were included in quantitative proteomic analysis using in-gel stable isotope labeling of proteins in combination with mass spectrometry. The quantified proteins were grouped into several functional groups, mainly into energy metabolism, photosynthesis, proteolysis, protein synthesis and proteins related to defense and stress. 70kDa heat shock protein showed the greatest increase in abundance under drought of all the proteins, suggesting its role in protecting plants against stress by re-establishing normal protein conformations and thus cellular homeostasis. The abundance of proteins involved in protein synthesis also increased under drought stress, important for recovery of damaged proteins involved in the plant cell's metabolic activities. Other important proteins in this study were related to proteolysis and folding, which are necessary for maintaining proper cellular protein homeostasis. Taken together, these results reveal the complexity of pathways involved in the drought stress response in common bean stems and enable comparison with the results of proteomic analysis of leaves, thus providing important information to further understand the biochemical and molecular mechanisms of drought response in this important legume.