Abstract: 【Objective】 Endo polygalacturonases (endoPGs) is considered to be one of the important pathogenic factors. The objectives of this study are to clone and compare endoPGs from the strong pathogenic strain YC-9 and the weak pathogenic strain LF-2 from Rhizoctonia solani, analyze the sequence features, evolutionary relationships and expression characteristics of endoPG1 and endoPG2, and to provide a theoretical foundation for clarifying molecular mechanism of the pathogenicity. 【Method】 Degenerate primers were developed based on the sequence of different endoPGs from plant pathogens in GenBank, and partial cDNA fragments of the strains YC-9 and LF-2 were firstly acquired, then the full-length cDNA sequences were cloned through RACE techniques, and the conserved domains and sequence features of the genes were analyzed by bioinformatics’ methods. A phylogenetic tree was constructed using the MEGA 4.0 software, and the relative expression characters of endoPG1 and endoPG2 were also analyzed by real-time RT-PCR. 【Result】 Two endo polygalacturonases genes were cloned and named as endoPG1 and endoPG2. The genes possessed the conserved domains of PLNO3003 gene superfamily. The open reading frame (ORF) of the full length cDNA was 1 086 bp, encoding a protein of 361 amino acid residues. Differences between endoPG1 and endoPG2 were indicated by comparing the full-length cDNA sequences and transmembrane regions of prediction protein. The PLNO3003 subunit phylogenetic tree was constructed, which showed that the corresponding amino acid sequences of endoPGs from R. solani formed an independent branch, and that of endoPG1 and endoPG2 had the highest homology. Real-time RT-PCR demonstrated that the expression of endoPG1 and endoPG2 were more obviously up-regulated in hyphae of inoculated tobacco leaves than in hyphae of non-inoculated ones, and the expression quantity of endoPG1 was higher than that of endoPG2. 【Conclusion】 The full cDNA sequences of endoPG1 and endoPG2 were successfully cloned from tobacco target spot disease of R. solani, and both have conserved domains of PLNO3003 gene superfamily, and it has obviously differences between transmembrane regions of prediction protein of endoPG1 and endoPG2. Phylogenetic analysis showed that the corresponding amino acid sequences of endoPG1 and endoPG2 have a highest homology relationship. Finally the endoPG1 and endoPG2 gene expression can be obviously induced by interaction with tobacco and the strong and weak pathogenicity strains in YC-9 and LF-2 have obvious differences.

Key words: Rhizoctonia solani , endoPGs , cloning , gene expression