Deciphering the Molecular Variations of Pine Wood Nematode Bursaphelenchus xylophilus with Different Virulence

Abstract

Bursaphelenchus xylophilus is the causative agent of pine wilt disease which has caused huge economic losses in many countries. It has been reported that two forms of pine wood nematodes existed in its native region, i.e., with strong virulence and weak virulence. However, little is known about the molecular differences between the two forms. To better understand their molecular variations, transcriptome and genome sequences of three strongly virulent and one weakly virulent strains were analyzed. We found 238 transcripts and 84 exons which showed notable changes between the two virulent forms. Functional analyses of both differentially expressed transcripts and exons indicated that different virulence strains showed dissimilar nematode growth, reproduction, and oxidoreductase activities. In addition, we also detected a small number of exon-skipping events in B. xylophilus. Meanwhile, 117 SNPs were identified as potential genetic markers in distinguishing the two forms. Four of them were further proved to have undergone allele specific expressions and possibly interrupted the target site of evolutionary conserved B. xylophilus miR-47. These particular SNPs were experimentally verified by including eight additional strains to ensure the validity of our sequencing results. These results could help researchers to better diagnose nematode species with different virulence and facilitate the control of pine wilt disease.

Selection of Reliable Reference Genes for RT-qPCR Analysis of Bursaphelenchus mucronatus Gene Expression From Different Habitats and Developmental Stages

“…The unstable expression of ACT has also been confirmed in other species ( Tong et al, 2009 ; Zhu et al, 2013 ; Yan et al, 2014 ). However, a number of previous reports have selected ACT as a reference gene in B. xylophilus ( Qiu et al, 2013 ; Xu et al, 2015 ; Deng et al, 2016 ; Ding et al, 2016 ), and, to the best of our knowledge, no previous studies have systematically examined its expression stability in B. xylophilus . As B. xylophilus is a sister species to B. mucronatus , and morphological and biological characteristics are very similar in the two species ( Mamiya and Enda, 1979 ), B. xylophilus may have arisen from its ancestor B. mucronatus in eastern Asia ( Kanzaki and Futai, 2002 ), and further research is needed to elucidate the expression stability of ACT in B. xylophilus .…”

Population variation in traits of Deladenus siricidicola that could influence the biocontrol of Sirex noctilio in South Africa

“…However, virulence is likely to be a complex trait (Semblat et al 2000) and unlikely to be easily linked to single genetic markers (Aikawa et al 2013). For example, Ding et al (2016) identified 117 single nucleotide polymorphic markers (SNPs) linked to virulence in the pine wood nematode Bursaphelenchus xylophilus following genome and transcriptome sequencing of B. xylophilus virulent and avirulent strains. This follows the common application of ITS-RFLP marker (Iwahori et al 1998, Aikawa et al 2003, 2006, which was shown not to be reliable in distinguishing virulence of B. xylophilus strains (Aikawa et al 2013).…”

Identifying Virulence-Associated Genes Using Transcriptomic and Proteomic Association Analyses of the Plant Parasitic Nematode Bursaphelenchus mucronatus

“…More than 3 Mb of genetic variations were investigated as single-nucleotide polymorphisms (SNPs) or small indels between different Japanese B. xylophilus isolates, and the genetic diversity was involved with their virulence and ecological characteristic differences [ 12 ]. Meanwhile, a number of transcripts and exons revealed remarkable differences between the strongly and weakly virulent Chinese B. xylophilus isolates, and functional study of those differences suggested that various virulence B. xylophilus isolates showed differences in their development, propagation, and oxidoreductase activities [ 43 ]. Similarly, there were considerable differences in strongly and weakly virulent isolates of both nematode species.…”