Abstract

Pine wilt disease (PWD), which is caused by pine wood nematode (PWN),Bursaphelenchus xylophilus has become a widespread threat to forests. Recently, more and more researches indicate that bacteria associated with PWN play an important role in pine wilt. We previously found that flagellin secreted from Pseudomonas fluorescensGcM5-1A could cause the death of suspension cells of Pinus thunbergii in vitro, but the mechanism is not clear. In this paper, flagellin of P. fluorescens GcM5-1A was found to interact with suspension cells, which resulted in disintegration of nuclei and degradation of genomic DNA. Inoculation test indicated that population levels of PWN and P. fluorescensGcM5-1A inoculated on dead callus of P. thunbergii either pretreated with flagellin or caused by heat treatment were much larger than those inoculated on live callus, respectively. Furthermore, flagellin alone could also promote the propagation of PWN and its carrying P. fluorescens GcM5-1A. The results implied that toxins such as flagellin secreted by bacteria associated with PWN might participate in the pathogenesis of PWD by inducing host cell death and promoting propagation of the 2 pathogens PWN and bacteria it carries.

Key words: Flagellin, Pinus thunbergii, callus, propagation, pine wood nematode,Pseudomonas fluorescens GcM5-1A.