The full-length cDNA of one ARF gene named DlARF5a(GenBank accession number:KF739401)was cloned from embryogenic callus of Dimocarpus longan by the RT-PCR combined with RACE method.Then the mRNA transcription level of the gene in the process of somatic embryogenesis was determined by qRT-PCR(real-time reverse transcription PCR) method.And the expression of ARF5a-GFP fusion protein in onion epidermal cells revealed its subcellular localization.The results indicated the complete cDNA sequence of DlARF5a was 3 322 bp containing 2 829 bp ORF encoding 942 amino acid,with 5′ and 3′ untranslated regions(UTR) of 212 bp and 258 bp,respectively.Bioinformatics analysis suggested that DlARF5a was probably a soluble protein,and functioned in the cytoplasm and consisted of a B3,Auxin-resp and AUX-IAA conservative district and structural function domain,and a Gln,Ser and Leu-rich middle region,which was considered as an activation domain.Phylogenetic analysis showed that protein encoded by DlARF5a had close genetic relationship with ARF5 in Citrus sinensis.The qPCR detection showed that DlARF5a had a remarkable rise in the expression levels at globular embryo and torpedo embryo stages,but the nadir mRNA transcription level of DlARF5a gene occurred at the cotyledonary stage(stage 6),demonstrating that DlARF5a was relevant to the torpedo embryo morphogenesis during longan somatic embryogenesis.The subcellular localization assays showed that the DlARF5a protein was located in the cytoplasm without adding the exogenous auxin IAA by confocal microscopy.Whereas,DlARF5a protein was located in the cell membrane,cytoplasm and nucleus under 1.0 mg/L IAA treatment,wich can be speculated that DlARF5a protein was able to change its spatial location in the cells in response to the external IAA.