Protist-Type Lysozymes of the Nematode Caenorhabditis elegans Contribute to Resistance against Pathogenic Bacillus thuringiensis

Abstract

Pathogens represent a universal threat to other living organisms. Most organisms express antimicrobial proteins and peptides, such as lysozymes, as a protection against these challenges. The nematode Caenorhabditis elegans harbours 15 phylogenetically diverse lysozyme genes, belonging to two distinct types, the protist- or Entamoeba-type (lys genes) and the invertebrate-type (ilys genes) lysozymes. In the present study we characterized the role of several protist-type lysozyme genes in defence against a nematocidal strain of the Gram-positive bacterium Bacillus thuringiensis. Based on microarray and subsequent qRT-PCR gene expression analysis, we identified protist-type lysozyme genes as one of the differentially transcribed gene classes after infection. A functional genetic analysis was performed for three of these genes, each belonging to a distinct evolutionary lineage within the protist-type lysozymes (lys-2, lys-5, and lys-7). Their knock-out led to decreased pathogen resistance in all three cases, while an increase in resistance was observed when two out of three tested genes were overexpressed in transgenic lines (lys-5, lys-7, but not lys-2). We conclude that the lysozyme genes lys-5, lys-7, and possibly lys-2 contribute to resistance against B. thuringiensis, thus highlighting the particular role of lysozymes in the nematode's defence against pathogens.

Secreted Proteomes of Different Developmental Stages of the Gastrointestinal Nematode Nippostrongylus brasiliensis

“…This family of proteins has been identified at the transcript level in other hookworms (26) and in the secretome of adult H. polygyrus (39). In addition, in the nematode C. elegans and the slime mold Dictyostelium discoideum lysozyme has been reported to exert an antimicrobial and bacteriolytic effect, which is likely to be associated with its expression in both developmental stages (52,53).…”

Quantitative proteome analysis of Caenorhabditis elegans upon exposure to nematicidal Bacillus thuringiensis

“…The Clec-4 gene in C. elegans has been identified previously as transcriptionally induced both in response to E. coli heterologously expressing the nematocidal Bt toxin Cry5B [17] and to Bt spore crystals of the same strain used in this study [14].…”

“…C. elegans potentially synthesizes 15 lysozymes belonging to the two different classes, namely of the invertebrate-type and the protist-type. Transcriptional analysis of the protist-type lysozyme genes in C. elegans after Bt infection has previously been performed [14]. The four protist-type lysozymes quantified here (numbers in brackets) show changes in agreement with qPCR results of a previous study [14],with LYS-1 (1.9 fold) and LYS-2 (2.2 fold) strongly increased, LYS-8 (1.2 fold) slightly increased and LYS-4 (0.6 fold) strongly decreased.…”

“…The pathogenic strain (B-18247) shows nematicidal activity in both its spore crystal mixtures and purified endotoxin crystals [10]. The second strain (DSM350) has been shown to be non-pathogenic by using survival assays [11][12][13][14][15]. Furthermore, exposed nematodes did not show signs of intestinal damage [11,12] and no reduction in nematode population growth, nematode body size, or feeding behavior was observed, in contrast to the effects caused by the nematicidal B-18247 [12][13][14][15].…”

Antimicrobial effectors in the nematode Caenorhabditis elegans : an outgroup to the Arthropoda

“…Silencing of either lys-7 or ilys-2 led to higher susceptibility towards the pathogen M. nematophilum [68]. Gene knock-out of lys-2, lys-5 and lys-7 enhanced susceptibility to pathogenic B. thuringiensis, while overexpression of lys-5 and lys-7 but not lys-2 enhanced resistance relative to a non-pathogenic control [69]. Furthermore, ilys-2 and lys-5 RNAi-treated worms are more susceptible to S. aureus infection [23].…”