Transcriptional and morphological changes in the transition from mycetophagous to phytophagous phase in the plant‐parasitic nematode Bursaphelenchus xylophilus

Summary Drastic physiological and morphological changes in parasites are crucial for the establishment of a successful infection. The nematode B ursaphelenchus xylophilus is the pathogenic agent of pine wilt disease, and little is known about the physiology and morphology in this nematode at the initial stage of infection. In this study, we devised an infection system using pine stem cuttings that allowed us to observe transcriptional and morphological changes in the host‐infecting phytophagous phase. We found that 60 genes enriched in xenobiotic detoxification were up‐regulated in two independent post‐inoculation events, whereas down‐regulation was observed in multiple members of collagen gene families. After 48 h of inoculation, the tails in some of the adult females exposed to the host changed in morphology. These results suggest that B . xylophilus may change its physiology and morphology to protect itself and to adapt to the host pine wood environment.