Genome-wide transcriptional analysis of submerged lotus reveals cooperative regulation and gene responses.

Flooding severely limits plant growth even for some aquatic plants. Although much work has been done on submergence response of some important crop plants, little is known about the response mechanism of aquatic plants, i.e. lotus (Nelumbo nucifera). In this study, we investigated the genome-wide regulation lotus genes in response to submergence stress by high-throughput mRNA sequencing. A total of 4002 differentially expressed genes (DEGs) in lotus upon submergence stress. Among them, 1976 genes were up-regulated and 2026 down-regulated. Functional annotation of these genes by Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis revealed that they were mainly involved in processes of oxidation-reduction, abiotic stimuli, cellular metabolism and small molecule metabolism. Based on these data, previous work and quantitative RT-PCR (RT-qPCR) validation, we constructed a cooperative regulation network involved in several important DEGs in regards to the antioxidant system, disease resistance, hypoxia resistance and morphological adaptation. Further work confirmed that several innate immunity genes were induced during submergence and might confer higher resistance to lotus rot disease. In conclusion, these results provide useful information on molecular mechanisms underlying lotus responses to submergence stress.