Bursaphelenchus xylophilus: opportunities in comparative genomics and molecular host-parasite interactions

Abstract

Most Bursaphelenchus species are fungal feeding nematodes that colonize dead or dying trees. However, Bursaphelenchus xylophilus, the pine wood nematode, is also a pathogen of trees and is the causal agent of pine wilt disease. B. xylophilus is native to North America and here it causes little damage to trees. Where it is introduced to new regions it causes huge damage. The most severely affected areas are found in the Far East but more recently B. xylophilus has been introduced into Portugal and the potential for damage here is also high. As incidence and severity of pine wilt disease are linked to temperature we suggest that climate change is likely to exacerbate the problems caused by B. xylophilus and, in addition, will extend (northwards in Europe) the range in which pine wilt disease can occur. Here we review what is currently known about the interactions of B. xylophilus with its hosts, including recent developments in our understanding of the molecular biology of pathogenicity in the nematode. We also examine the potential developments that could be made by more widespread use of genomics tools to understand interactions between B. xylophilus, bacterial pathogens that have been implicated in disease and host trees.

Figure 1

Life cycle of B. xylophilus. Image of Monochamus pupa provided by P. Naves, EFN‐INRB, Portugal.

Figure 2

Uptake of fluorescently labelled dsRNA by B. xylophilus adult. (A) Nematode viewed under light microscope; (B) same nematode viewed under fluorescence optics. Fluorescently labelled dsRNA was generated using the Megascript RNAi kit (Ambion) following the manufacturer's instructions but substituting Cy3‐labelled UTP (GE Healthcare) for unlabelled UTP in the synthesis reaction. Nematodes were incubated in the labelled dsRNA for 24 h in the dark on a rotator in the presence of 3 mm spermidine and 0.05% gelatin.