In this research,a novel SEP3 gene,named CgSEP3(GenBank accession number KF924272),was isolated from Cymbidium goeringii by RT-PCR and RACE-PCR techniques.Sequence analysis showed that this gene contains an open reading frame of 732 bp encoding a putative protein of 243 amino acids.The deduced protein showed high identity with other SEP3 proteins from different species,phylogenetic tree analysis also indicated that CgSEP3 belongs to SEP clade of AP1/AGL9 subfamily.Real-time quantitative PCR demonstrated that CgSEP3 was expressed in all flower organs,highly expressed in lips,lateral petals and sepals,and the lowest in young ovary and columns.In addition,CgSEP3 was expressed in different development stages of flower,with the highest expression in flower buds(1-2 cm),and the lowest in opened flower.These results displayed that CgSEP3 may regulate the petals and sepals formation of C.goeringii.