The occurrence of intron retention on Bx‐pel‐2 gene enhanced the cell wall degrading ability of Bursaphelenchus xylophilus

BACKGROUND Pectate lyase is the crucial cell‐wall‐degrading enzyme exists in Bursaphelenchus xylophilus . It helped the nematode to penetrate host cell wall during pine wilt disease (PWD). Several pectate lyase genes had been found in Bursaphelenchus xylophilus but no intron retention events were identified. RESULTS Here, we demonstrated that intron retention (IR) was occurred on Bx‐pel‐2 gene while the spliced introns were varied among different nematode isolates (AMA3: 6 types; ZJ07: 5 types; JX06:4 types; GD10:4 types). Based on the sequence feature analysis, the IR of Bx‐pel‐2 introduced new premature termination codons and motif sites and could be recognized as exitron. The overall expression of IR isoforms was lower than canonical isoform (N‐IR) during the development of pine wilt disease. The secondary structure of IR encoded proteins were differed from N‐IR protein but all the proteins showed a good affinity with D‐galacturonic acid (main chain of pectin) according to molecular docking analysis (binding energy >5.0 Kcal/mol). Western blot and enzyme quantification assays verified that IR encoded proteins exhibited significant higher pectate degrading ability compared with N‐IR protein. CONCLUSION The IR on Bx‐pel‐2 gene could be recognized as exitron to enhance the cell wall degrading ability of B. xylophilus . This study will expand the current understanding of post‐transcriptional regulation mechanism of B. xylophilus as well as provide more accurate molecular target site for controlling this devastating disease.