Comparative Proteomic Analysis of Two Sugar Beet Cultivars with Contrasting Drought Tolerance

In a changing climate, drought stress accounts for significant crop yield loss. To test the hypothesis that proteins play an important role in plant drought tolerance, we conducted physiological and proteomic analyses to investigate the stress responses of two sugar beet (Beta vulgaris L.) cultivars with contrasting tolerance to drought stress. Under drought, the tolerant cultivar had higher relative water content, root length, dry weight, and root system area than the drought-sensitive cultivar. In addition, the tolerant cultivar had higher antioxidant enzyme activities than the sensitive cultivar to prevent ROS damage under drought stress conditions. Proteomic analysis resulted in identification of 23 and 27 drought-responsive proteins in the sensitive and tolerant cultivars, respectively. Based on their functions, these proteins were classified into nine categories. Many proteins in several different biological processes showed different abundance patterns between the genotypes (for example, oxygen-evolving enhancer proteins, choline monooxygenase, and malate dehydrogenase). Although some proteins changed similarly in trend between the two genotypes, they showed different levels of changes (for example, S-adenosylmethionine synthase). Furthermore, the poor correlation between transcription and protein levels was confirmed in this study. Our findings would lead to an improved understanding of the integrated physiology and proteome responses of the different sugar beet genotypes under drought stress.