A comparative proteomic study of drought-tolerant and drought-sensitive soybean seedlings under drought stress

Drought is a major factor limiting plant growth causing yield reduction in crops; hence the characterisation of drought tolerance and the development of drought-tolerant crop varieties have been a goal of many crop breeding programs. Using the proteomics approach, we compared the differential protein abundance of drought-tolerant and drought-sensitive soybean leaves subjected to mild or severe drought stress. Proteins were extracted and separated using two-dimensional electrophoresis. Those protein spots with significant and more than 2-fold difference in abundance, 174 in total, were further analysed and 102 proteins were positively identified. Around 38.5% of these proteins were related to energy metabolism and photosynthetic functions, followed by those associated with defence response (36.4%) and protein metabolism (25.2%). Severe drought resulted in a greater number of proteins with differential abundance. Genotypes responded differently to drought stress with the tolerant genotype showing a higher capacity for reactive oxygen species scavenging and maintaining energy supply than the sensitive genotype. The sensitive genotype had a greater number of proteins with significant differential abundance than the tolerant genotypes due to drought. The different patterns in protein abundance induced by drought stress may potentially be utilised to screen and select candidate soybean lines with improved drought tolerance.