Differential Expression of Two-Component System–Related Drought-Responsive Genes in Two Contrasting Drought-Tolerant Soybean Cultivars DT51 and MTD720 Under Well-Watered and Drought Conditions

Two-component systems (TCSs) have been shown to participate in plant responses to drought. In this study, results of real-time quantitative PCR (RT-qPCR) of 26 selected dehydration-responsive TCS-related genes in roots and shoots of two Vietnamese soybean cultivars (DT51 and MTD720) with contrasting drought-tolerant phenotypes suggest a positive correlation between the number of drought-inducible TCS genes and their drought-tolerant ability. In addition, expression analyses of the roots and shoots indicated that DT51 and MTD720 had distinct drought-responsive TCS expression profiles, suggesting that expression of TCS-related genes are genotype and tissue dependent. Furthermore, nine TCS genes (GmHK07, 16, GmHP08, GmRR04, 16, 32, 34, GmPRR39, and 44) potentially associated with enhanced drought tolerance were identified. Particularly, GmRR34, showing its higher expression levels under both normal and drought conditions in DT51 roots versus MTD720 roots, might be a potential positive regulator of drought tolerance. On the other hand, GmPRR44 was highly recommended as a potential negative regulator of drought tolerance because it exhibited lower expression levels in both tissues of the drought-tolerant DT51 than in those of the drought-sensitive MTD720 under both stressed and unstressed conditions. These two genes deserve in-depth characterization as promising candidates for development of soybean cultivars with improved drought tolerance by using genetic engineering.