An unknown protein gene related to somatic embryogenesis had been discovered and named Dimocarpus longan unknown protein gene 3 (DlUP-3) during the proteomic analysis of early somatic embryogenesis in longan.It was cloned by using degenerate oligonucleotide primers together with RACE.The full-length cDNA sequence of DlUP-3 gene was 1 681 bp.It contains a 1 017-nucleotides-long open reading frame (ORF) which encoded a protein of 338 amino acid residues (GenBank No.GQ167202).Bioinformatics analysis showed that the molecular weight of DlUP-3 protein is 36 854.2 Da with pI 9.05,it is a member of the Ras protein superfamily,which has ATP/GTP-binding site motif A (P-loop) binding site,Ras_like_GTPase superfamily module,hydrophilic characteristics and transmembrane properties but no signal peptide.Random coils are the most maximum structural elements and were found spreading in the whole polypeptide chain.The expression of DlUP-3 gene was also investigated during longan somatic embryogenesis according to the results of real-time quantitative PCR.Its expression was the lowest at the the friable-embryogenic callus stage and the highest at globular embryos stage.There had an elementary understanding to the important function of DlUP-3 gene during longan somatic embryogenesis,especially at globular embryos stage.This result laid a foundation for the further study on the function of DlUP-3 gene during longan somatic embryogenesis.