Bursaphelenchus xylophilus is known to be a major pathogen of the pine wilt disease (PWD). The pathogenecity of PWD is considered to be related to cell wall-degrading enzymes such as endoglucanases, expansins and pectate lyases (PELs). Two PELs, Bx-PEL1 and Bx-PEL2 are known to be expressed in B. xylophilus and regarded as a putative pathogenic factor. Recently, we developed stage-specific expressed tag library of B. xylophilus and identified a novel Bx-PEL3. We cloned Bx-PEL3 gene with RT-PCR, which showed high similarity to previously reported Bx-PELs. Phylogenetic analysis revealed that PEL3 was much closer to Bx-PELs than any other PELs. PEL3 has a conserved intron site as found in other Bx-PELs in the genomic DNA. Quantitative real-time PCR analysis revealed that Bx-PEL1 and Bx-PEL2 were more predominant in B. xylophilus than the Bx-PEL3. Recombinant Bx-PEL3 showed the activity for polgalacturonic acid and its physical conditions such as PH and Ca2+concentration for optimized activity were 9.0 and 0.5 mM, respectively. The localization of PEL3 transcript is the anterior body of B. xylophilus, near the esophageal gland. Taken together, these results suggest that a novel PEL3 gene is biochemically functional and can play a role as a putative pathogenic factor like other PELs.

The pinewood nematode (PWN, Bursaphelenchus xylophilus) is known to be a major pathogen of the pine wilt disease (PWD). However molecular pathology of B. xylophilus is not completely understood, the pathogenecity of PWD is related to cell wall-degrading enzymes such as endoglucanases, expansins and pectate lyases (PELs). Recently, we developed stage-specific expressed tag library of B. xylophilus and identified a novel PEL, Bx-PEL3. We cloned Bx-PEL3 gene with RT-PCR, which showed high similarity to previously reported Bx-PELs. Phylogenetic analysis revealed that PEL3 was much closer to PELs of B. xylophilus than any other PELs. PEL3 has a conserved intron site as found in Bx-PEL2 in the genomic DNA analysis. Quantitative real-time PCR analysis revealed that Bx-PEL1 and Bx-PEL2 were more predominantly expressed than the Bx-PEL3 in B. xylophilus. The difference of expression level among Bx-PELs according to growth condition suggests that each Bx-PEL plays different biochemical role in the pathogenesis of the PWD.