Gene Expression Profiling in Sugarcane Genotypes During Drought Stress and Rehydration

The study aimed to assess the molecular responses of sugarcane genotypes exposed to water stress and rehydration. Six sugarcane varieties that show differential tolerance to drought were planted in the pots with three replications and subjected to gradual drought by withholding water for 2, 6 and 10 days and rehydration for 2, 6 and 10 days after the onset of treatment (DAT) at 60 days after planting. To analyze the physiological status, relative water content and cellular membrane injury were measured. Among the six varieties, two varieties, viz. Co 06022 and Co 99004, retained high relative water content and cell membrane injury recorded was also low during severe drought stress. Sugarcane variety Co 8021 was the most vulnerable to drought stress. The relative water content reduced drastically at 2 days of stress and also maximum membrane injury was observed as stress progressed. Signs of wilting were observed in 2 days, while Co 06022 and Co 99004 showed slight wilting only at 10 days of stress. Examination of differentially expressed genes and transcription factors indicated that ABRE-binding factor, trehalose 6-phosphate synthase, DREB2, SNAC1, dehydrin and early responsive to dehydration (ERD4) showed high-level transcript accumulation during initial stress and gradually declined as stress progressed to 10 days in most genotypes. Invertase and calmodulin functional proteins were overexpressed at both stress and recovery stages. Expression levels of most genes reverted back to their control levels during recovery. Results were validated in shoots and leaves by quantitative real-time PCR.