ABSTRACT
Objective: To clone CDS sequence of Dioscorea opposita SUS gene and analyze the protein structure,in order to provide a theoretical basis for the regulation mechanism of SUS gene and the synthesis mechanism of D.opposita polysaccharides.Method: Total RNA in D.opposita was extracted and reverse-transcribed into first strand of cDNA.Specific primers were designed according to an annotated SUS gene sequence obtained from the laboratory D.opposita genome database,and the coding region of the SUS gene was obtained by gene cloning technique and the protein sequence characteristics were analyzed by protein prediction analysis software.Result: A 2 448 bp gene sequence was cloned with a complete open reading frame (ORF).The gene was named DoSUS1.The formula of protein encoded by DoSUS1 gene in D.opposita was C4209H6534N1115O1205S23,and the molecular weight was 9 788.32,the total number of amino acids was 815,the theory isoelectric point (PI) was 6.10,the extinction coefficient was 110 505,the aliphatic index (AI) was 94.15,the instability index was 32.18,and the grand average of hydropathicity (GRAVY) was-0.225.It was a stable and soluble acidic protein.There were phosphorylation sites in the DoSUS1 amino acid sequence,with no transmembrane region and signal peptide.The secondary structure and the tertiary structure showed that DoSUS1 was an α class protein.Functional domain predictions showed that DoSUS1 had sucrose synthesis domain and glycosyl transfer domain.The homology alignment showed that the amino acid sequence of DoSUS1 was more than 80% similar to the amino acid sequence of the aligned monocots.The phylogenetic tree showed that DoSUS1 was closely related to SUS of monocotyledon evolution.Conclusion: The coding sequence of SUS gene was cloned from D.opposita for the first time,and its protein structure was analyzed to lay a foundation for further studying the roles of SUS in the growth and polysaccharide synthesis of D.opposita.