Abstract: To explore the sequence characteristics of β-glucosidase gene VmGluI from Valsa mali var. mali (Vmm)and analyze its expression pattern in the process of pathogen infection,the cDNA sequence of VmGluI was amplified from the strong pathogenic strain LXS080601 by using RT-PCR technology.The phylogenetic relationship,physicochemical properties and secondary structure of the protein coded by VmGluI were analyzed by bioinformatics software.The expression levels of VmGluI in apple tiwgs(Malus domestica Borkh.Fuji) inoculated by Vmm were analyzed by Real-time quantitative PCR.The results showed that the cDNA sequence of VmGluI from Vmm was obtained and its GenBank accession number was KY646110.The open reading frame of 1 689 bp encoded 562 amino acid residues with a predicted molecular weight of 62.7 kDa.VmGluI shared characteristic conserved domains of glycosyl hydrolase family 1. α -helices and random coils were its main elements of secondary structure of VmGluI,and β-turns were less.Multiple sequence alignment and phylogenetic tree analysis showed that the encoded protein had the closest genetic relationship with β-glucosidase genes from Vmm (KUI68239.1) and V.mali var. pyri (KUI56905.1),and the similarities of amino acid sequences were 98.7% and 87.8%,respectively.However,the relationship between VmGluI and other β-glucosidase genes from non-pathogenic fungi was far away.The Real-time quantitative PCR results showed that VmGluI was significantly up-regulated in Fuji tiwgs after inoculation by Vmm.Thus,the authors speculated that VmGluI could paly an important role in the pathogenic process of Vmm.The expression level of VmGluI began to increase significantly in detached twigs at 48 h and the highest expression level was 6.3 times higher than that in the control at 72 h.However,the gene expression level increased significantly at 12 h in living twigs,which was 11.2 times higher than that in the control at 96 h.Although there was a low level of gene expression at 48 h,the amount of gene expression was 16.8 times higher than that in the control at 96 h.The results indicated that expression levels and the time course changes of VmGluI were obvious difference in detached and living twigs inoculated with Vmm.

Key words: Valsa mali var.mali, VmGluI, Gene cloning, Bioinformatics analysis, Gene expression

CLC Number: 

• Q78

• S436.03