Transcriptomic and physiological studies identify cues for germination stage oxygen deficiency tolerance in rice

Abstract

Submergence during germination imposes germination stage oxygen deficiency (GSOD). Natural variation in anaerobic germination potential (AGP), manifested by their differences in GSOD tolerance, is available in rice. Present study was performed to understand differential responses of two rice cultivars, Naveen and AC41620 (susceptible and tolerant to GSOD, respectively) subjecting them to 48-h continuous submergence during germination. Transcriptome analysis revealed more elaborate regulation of gene expression in AC41620 compared to Naveen. Validation of transcriptome data through q-PCR of selected genes and biochemical analysis related to carbohydrate metabolism, anaerobic respiration and oxidative stress tolerance were more significant in AC41620, than Naveen. The time-course enzyme assays for continued submergence suggested that the activity of α-amylase, pyruvate decarboxylase and alcohol dehydrogenase increased under continuous submergence. Efficient nitrogen metabolism supported by increased nitrate and nitrite reductase activities and better handling of reactive oxygen species (ROS) because of increased antioxidant enzyme activities were found to be associated with GSOD in AC41620. Increased ethylene production along with action of ABA, GA and G-proteins aided in GSOD tolerance of AC41620. The differentially expressed genes identified in the present study will serve as a useful genomic resource for extending our understanding of molecular mechanism of anaerobic germination vis-à-vis GSOD tolerance in rice.