In most species, sex is determined by genetic or environmental factors. Nematode sex determination pathways might have evolved by “bottom-up” accretion from the most downstream regulator, tra-1. By contrast, our genetic screen for sex differentiation mutants identifies a Bursaphelenchus ortholog of tra-1, the major output of the C. Moreover, the protein sets of these nematodes lack genes involved in X chromosome dosage counting or compensation. There is no detectable difference in male and female chromosomes, nor any linkage to sexual phenotype. Here we analyze by sex-specific genome sequencing and genetic analysis sex determination in two fungal feeding/plant-parasitic Bursaphelenchus nematodes and find that their sex differentiation is more likely triggered by random, epigenetic regulation than by more well-known mechanisms of chromosomal or environmental sex determination. Sex determination mechanisms evolve surprisingly rapidly, yet little is known in the large nematode phylum other than for Caenorhabditis elegans, which relies on chromosomal XX-XO sex determination and a dosage compensation mechanism. This easy-to-set-up and run method for genetic marker identification will be useful for numerous laboratories studying biological invasions, but with limited resources and expertise in bioinformatics. The bioinformatics pipeline is user-friendly and requires little computational resources. We successfully isolated several pools of one hundred short gene regions for each assembled genome, which can be amplified in multiplex. 2000, Thaumetopoeapityocampa Denis & Schiffermüller, 1775). Sutton 1980, Erysiphealphitoides (Griffon & Maubl.) U. The pipeline's functionality was evaluated with sequenced genomes of five invasive or expanding pathogen and pest species in Europe (Armillariaostoyae (Romagn.) Herink 1973, Bursaphelenchusxylophilus Steiner & Buhrer 1934, Sphaeropsissapinea (fr.) Dicko & B. Previous studies have shown that intronic regions of these conserved genes generally contain several single nucleotide polymorphisms within species. This pipeline is based on: 1) an automated de novo genome assembly obtained from shotgun whole genome sequencing using paired-end Illumina technology 2) the isolation of single-copy genes conserved in species related to the studied emergent organisms 3) primer development for multiplexed short sequences obtained from these conserved genes. We developed a generic bioinformatics pipeline to rapidly isolate such markers with the goal for the pipeline to be applied in studies of invasive taxa from different taxonomic groups, with a special focus on forest fungal pathogens and insect pests. Analyses of genetic diversity are an efficient method to obtain this information rapidly, but require available polymorphic genetic markers. This lack of resources is a serious limitation to our understanding of the origin of emergent populations, their ability to adapt to new environments and to predict future consequences to biodiversity. Many of these events involve species with poor or no genomic resources (called here "orphan species"). This increase leads to serious threats to the genetic and species diversity of numerous ecosystems. xylophilus, provide a practical marker to genotype copy number variations and may aid in population classification.įor several decades, an increase in disease or pest emergences due to anthropogenic introduction or environmental changes has been recorded. Our results provide new insights into the pathogenicity of B. xylophilus strains with different virulence. Consequently, we were able to further identify the copy number variations of glycoside hydrolase 45 genes among B. Additionally, tandem repeat variations within coding regions were also detected between different copies of glycoside hydrolase 45 genes that could result in changes in protein sequences and serve as an effective biological marker to detect copy number variations among different B. In this study, we determined that two of the glycoside hydrolase 45 genes evolved to maintain multiple copies with distinct expression levels, enabling the nematode to infect a variety of pine hosts. Previous studies ignored the possibility of copy number variations of such genes. xylophilus are reported to have been acquired by horizontal gene transfer from fungi and are responsible for cell wall degradation during nematode infection. The pine wood nematode Bursaphelenchus xylophilus parasitizes millions of pine trees worldwide each year, causing severe wilt and the death of host trees.
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