Isolation and molecular identification of nematode surface mutants with resistance to bacterial pathogens

Abstract

Numerous mutants of the nematode Caenorhabditis elegans with surface abnormalities have been isolated by utilizing their resistance to a variety of bacterial pathogens (Microbacterium nematophilum, Yersinia pseudotuberculosis and two Leucobacter strains), all of which are able to cause disease or death when worms are grown on bacterial lawns containing these pathogens. Previous work led to the identification of nine srf or bus genes; here we report molecular identification and characterization of a further ten surface-affecting genes. Three of these were found to encode factors implicated in glycosylation (srf-2, bus-5, bus-22), like several of those previously reported; srf-2 belongs to the GT92 family of putative galactosyltransferases, and bus-5 is homologous to human TGDS, which is implicated in Catel-Manzke syndrome. Other genes encoded proteins with sequence similarity to phosphatidylinositol phosphatases (bus-6), Patched-related receptors (ptr-15/bus-13), steroid dehydrogenases (dhs-5/bus-21) or glypiation factors (bus-24). Three genes appeared to be nematode-specific (srf-5, bus-10, bus-28). Many mutants exhibited cuticle fragility as revealed by bleach and detergent sensitivity; this fragility was correlated with increased drug sensitivity, as well as with abnormal skiddy locomotion. Most of the genes examined were found to be expressed in epidermal seam cells, which appear to be important for synthesizing nematode surface coat. The results reveal the genetic and biochemical complexity of this critical surface layer, and provide new tools for its analysis.

Exploring the mechanisms of host-specificity of a hyperparasitic bacterium (Pasteuria spp.) with potential to control tropical root-knot nematodes (Meloidogyne spp.): insights from Caenorhabditis elegans

“…Bah , biofilm absent from head; Bus , bacterially unswollen; Dar , deformed anal region; Gro , slow growth; Hbp , head biofilm present; Skd , skiddy locomotion). The majority of these genes that are responsible for altered pathogenicity in several different bacteria such as Microbacterium nematophilum , Yersinia pseudotuberculosis and strains of Leucobacter spp., and are associated with an altered cuticular surface coat (SC) ( O'Rourke et al., 2023 ). The cuticle SC, or glycocalyx, is rich in lipids and glycoproteins, the source of which is increasingly thought to be the seam cells ( Gravato-Nobre and Hodgkin, 2011 ; O'Rourke et al., 2023 ).…”

“…The majority of these genes that are responsible for altered pathogenicity in several different bacteria such as Microbacterium nematophilum , Yersinia pseudotuberculosis and strains of Leucobacter spp., and are associated with an altered cuticular surface coat (SC) ( O'Rourke et al., 2023 ). The cuticle SC, or glycocalyx, is rich in lipids and glycoproteins, the source of which is increasingly thought to be the seam cells ( Gravato-Nobre and Hodgkin, 2011 ; O'Rourke et al., 2023 ). These seam cells lie beneath the lateral mid-line and have an important role in regard to producing a diverse range of complex compounds that affect the ability of microorganisms to adhere and form biofilms.…”

“…Here, seam cells become key because they are an origin of the SC and important in the expression of mucins which are complex molecules that have a role in bacterial infection processes ( Parsons et al., 2014 ; O'Rourke et al., 2023 ). Noteworthy, is that in C. elegans the bus -8 gene, which encodes a glycosyltransferase, appears to have a dual role in epidermal morphogenesis.…”

“…Reviewing the work of (Phani et al, 2017;Phani et al, 2018a;Phani et al, 2018b) with M. incognita, there was clear evidence that Mi-FAR-1, Mi-SeBP-1 and Mi-muc-1 were all associated with hypodermal expression, but nothing to specifically to link them to seam cells. However, and interestingly, most of the genes identified in C. elegans involved in bacterial resistance were expressed by seam cells (O'Rourke et al, 2023) which are known to be hypodermal, located along each side of the nematode beneath the alae, and undergo repetitive replacement during the nematode's development (Page and Johnstone, 2007). Only Mi-muc-1 and Mi-SeBP-1 were primarily investigated by Phani et al (2018a;2018b) for their association with bacterial infection, the other, Mi-FAR-1 was primarily associated with retinol acquisition and had been shown to affect the interaction between the nematode and its plant host (Iberkleid et al, 2013).…”