Identification of Putative Aquaporin Genes and Their Expression Analysis under Hypoxic Conditions in Soybean [Glycine max (L.) Merr.]

The aims of this study were to detect plasma-membrane intrinsic protein type 2 (PIP2) genes of soybean (cv. Eiffel) and to analyze mRNA levels of these genes under normoxic (control) and hypoxic conditions. A sequence similarity search with cDNA sequences in soybean genome revealed three putative aquaporin genes with high homology to GmPIP2;2. The genes were designated GmPIP2 genes. The mRNA levels in roots of soybean seedlings were measured at 3, 6, 12, and 27 hr after hypoxic stress onset. The mRNA levels of all GmPIP2s showed dear diurnal changes in the control, meanwhile, those under hypoxic conditions were significantly down-regulated even at 3 hr after stress onset. These results suggest that the four GmPIP2 genes are transcriptionally co-regulated by the diurnal change and oxygen concentration in the surrounding environment, and the transcriptional regulation may be involved in adjustment of water-transport in roots of soybean seedlings.