A Lover and a Fighter: The Genome Sequence of an Entomopathogenic Nematode Heterorhabditis bacteriophora

Abstract

Heterorhabditis bacteriophora are entomopathogenic nematodes that have evolved a mutualism with Photorhabdus luminescens bacteria to function as highly virulent insect pathogens. The nematode provides a safe harbor for intestinal symbionts in soil and delivers the symbiotic bacteria into the insect blood. The symbiont provides virulence and toxins, metabolites essential for nematode reproduction, and antibiotic preservation of the insect cadaver. Approximately half of the 21,250 putative protein coding genes identified in the 77 Mbp high quality draft H. bacteriophora genome sequence were novel proteins of unknown function lacking homologs in Caenorhabditis elegans or any other sequenced organisms. Similarly, 317 of the 603 predicted secreted proteins are novel with unknown function in addition to 19 putative peptidases, 9 peptidase inhibitors and 7 C-type lectins that may function in interactions with insect hosts or bacterial symbionts. The 134 proteins contained mariner transposase domains, of which there are none in C. elegans, suggesting an invasion and expansion of mariner transposons in H. bacteriophora. Fewer Kyoto Encyclopedia of Genes and Genomes Orthologies in almost all metabolic categories were detected in the genome compared with 9 other sequenced nematode genomes, which may reflect dependence on the symbiont or insect host for these functions. The H. bacteriophora genome sequence will greatly facilitate genetics, genomics and evolutionary studies to gain fundamental knowledge of nematode parasitism and mutualism. It also elevates the utility of H. bacteriophora as a bridge species between vertebrate parasitic nematodes and the C. elegans model.

Variation in the Susceptibility of Drosophila to Different Entomopathogenic Nematodes

“…These differences in virulence reflect differences in both the rates at which fly larvae become infected with EPNs and the rates at which infected fly larvae succumb to the infection. All five of the Drosophila species tested have sequenced genomes (60), and six of the seven nematode species tested have sequenced or nearly sequenced genomes (61,62). A comparison of Drosophila genomes revealed that many immune-related genes evolve more rapidly than other genes and identified numerous species-specific differences in immune-related genes, including copy number differences in AMP genes (63).…”

Improved structural annotation of protein-coding genes in theMeloidogyne haplagenome using RNA-Seq

“…e.g. [2][3][4][5] Included in this list are those of two root-knot nematodes (RKN), Meloidogyne hapla 2 and Meloidogyne incognita. 3 Meloidogyne is a large genus of plant parasites that are distributed worldwide and cause substantial loss to agricultural production.…”

All the microbiology nematodes can teach us

“…Furthermore, since these nematode-bacterium complexes are pathogenic toward a wide range of insects, an additional goal in studying EPNs is improving their employability in insect pest control (Stock 2005). In particular, investigators are focusing on identifying EPNs traits associated with insect host range and successful parasitism to help improve their field efficacy, and on identifying EPN symbiont products with insecticidal properties, efforts facilitated by sequencing of both bacterial and nematode genomes (Duchaud et al 2003;Ciche 2007;Wilkinson et al 2009;Chaston et al 2011;Dillman, Mortazavi and Sternberg 2012;Bai et al 2013).…”