Leaf Proteomic Studies Reveal Cross-Tolerance to Abiotic Stresses in Soybean

Water stress (WS) and high temperatures (HS) have a negative effect on soybean crop productivity. During WS, soybean plants opt for survival through ion homeostasis and the conformations of proteins are perturbed as plant cells lose water, while HS leads to difficulties in flowering and fruiting. Proteomic studies were conducted to obtain insight into the effects of WS and HS on molecular and cellular functions. Two soybean cultivars (A: Slow wilting and high yielding; and B: High protein with moderate yield potential) were exposed to different heat and water stress conditions in plant growth chambers. Changes in the leaf protein composition were studied using 2-DE complemented with MALDI-TOF mass spectrometry. Thirty-nine proteins were differentially expressed in response to WS and HS in both cultivars. Gene ontology analysis revealed majority of the functional categories including photosynthesis, metabolism, transport, stress and defense, and glycolysis. Expression of proteins was largely affected to WS in Cultivar A, while HS affected their expression in cultivar B suggesting genetic variation for stress tolerance. Combined abiotic stresses (WS+HS) equally affected both cultivars. RT-PCR studies and enzyme assays of selected genes suggest a positive correlation with protein expression among the cultivars. Proteins involved in metabolism, glycolysis, photosynthesis, such as HSPs, enolase, rubisco activase, were over expressed during combined WS+HS stress in both cultivars. Based on protein interaction studies, we hypothesize the plant’s development of cross-stress tolerance.