Identification of transcription factors predominantly expressed in soybean flowers and characterization of GmSEP1 encoding a SEPALLATA1-like protein.

By microarray analysis and real-time RT-PCR, we identified 28 soybean flower-enriched transcription factors such as MADS-box proteins, zinc finger proteins, and MYB proteins. Among them, one MADS-box protein GmSEP1 was chosen for further analysis. GmSEP1 contains 8 exons and 7 introns, showing similar exon-intron structure with Arabidopsis SEP genes. Phylogenetic analysis also suggested that GmSEP1 belonged to AGL2/SEP subfamily and likely a soybean orthologue of Arabidopsis SEP1. Subcellular localization assay suggested that GmSEP1 was localized in nucleus. Semi-quantitative RT-PCR showed that GmSEP1 was predominantly expressed in reproductive organs including petal, sepal, stamen, carpel and seed. By real-time RT-PCR, we found that GmSEP1 was expressed with a low level in stamens of soybean mutant NJS-10Hfs in which some stamens are converted to petal-like structure. Further we found that expression of GmSEP1 was altered during the course of seed development and more accumulated in outer and inner integuments, epidermis and endothelium at the globular stage, heart stage and cotyledon stage and in seed coat parenchyma at the early maturation stage of seed development. Taken together, GmSEP1 might play important role in soybean reproductive development, in particular, in petal and seed coat development.