Cloning of Copper Chaperone for Superoxide Dismutase Gene CCS from Embryogenic Callus of Dimocarpus longan Lour. and Its Expression Analysis During Somatic Embryogenesis

Copper chaperone for superoxide dismutase gene(CCS) was cloned and its expression level was analyzed for elucidating its role during longan somatic embryogenesis.DlCCS gene was isolated by RT-PCR,containing a 960-nucleotideslong open reading frame(ORF) which encoded a protein of 319 amino acid residues.Bioinformatics analysis showed that the protein encoded by DlCCS with the signal peptide and transmembrane helices was hydrophilic,stable and acidic protein,located in the chloroplast.Homology researches with the deduced amino acid residues indicated that DlCCS gene had a high similarity to other plant CCS genes,and the predicted DlCCS polypeptide contained 3 distinct domains.The phosphorylation occurred mainly on serine,followed by threonine and thyosine residues.The DlCCS protein was involved in superoxide metabolism and metal ion transport process,and played a role of oxidation-reduction during longan somatic embryogenesis.qPCR results indicated that DlCCS was expressed at low levels from the friable-embryogenic callus(Stage 1) to the compact pro-embryogenic cultures(Stage 4).With further embroygenic development,its expression increased rapidly and peaked at the mature embryo stage(Stage 9),suggesting that DlCCS might play a major role in the middle and late developmental stages of longan somatic embryogenesis.