Nematode chitin synthases: gene structure, expression and function in Caenorhabditis elegans and the plant parasitic nematode Meloidogyne artiellia

Abstract

Although the presence of chitin in nematodes is well documented little is known about its synthesis in this phyletic group. The recently completed genome sequence of Caenorhabditis elegans predicts two sequences with homology to chitin synthases (chitin-UDP acetyl-glucosaminyl transferase; EC 2.4.1.16). We show that these genes are differentially expressed in a pattern that may reflect different functional roles. One gene is expressed predominantly in the adult hermaphrodite (the main egg-producing stage in the nematode) and later larval stages, which is consistent with a role in production of chitin for the eggshell. The other gene, however, is expressed in the cells that form the pharynx, and only in the period directly preceding a moult. These data suggest that the product of this gene is involved in synthesis of the feeding apparatus, which is replaced during each moult. We have also isolated a full-length genomic sequence of a chitin synthase orthologue from the plant parasitic nematode Meloidogyne artiellia. The single gene present in M. artiellia shows an expression pattern that is consistent with a role for the protein in production of the eggshell.

Neuron-specific knock-down of SMN1 causes neuron degeneration and death through an apoptotic mechanism

“…3S–X). The smn-1 knock-down transgenic strain carried as the selection marker a GFP reporter (GB301 p chs-2::gfp ), which is specifically expressed in 17 cell nuclei in the pharynx (33). This reporter is never expressed in D-type motor neurons.…”

Acidic chitinase primes the protective immune response to gastrointestinal nematodes

“…GI roundworms or nematodes, which, unlike the flatworm trematode S. mansoni , are known to contain chitin in their mouthparts, larval sheaths, and eggshells 3,4 , infect over 2 billion people, contributing to substantial morbidity and mortality worldwide 19 . We sought to understand the role of AMCase in host protection using the rodent nematode N. brasiliensis , which has been used extensively to study and model the immunobiology of human hookworm infestation 20 .…”

“…Chitin is the second most abundant polymer in nature, found as a structural component in fungi 1 , arthropods 2 , and parasitic nematodes 3,4 . Mammals do not synthesize chitin, but they express two known enzymes that digest chitin: acidic mammalian chitinase (AMCase) 5 and chitotriosidase 6 .…”

The C. elegans eggshell

“…C. elegans has two genes, chs-1 and chs-2 , that encode chitin synthase, the enzyme that polymerizes UDP-N-acetyl-glucosamine into chitin (Zhang et al, 2005; Veronico et al, 2001). Animals homozygous for the deletion mutation, chs-1(ok1120) or depleted of CHS-1 by RNAi do not produce any viable progeny.…”

“…CHS-1 resides in membranes and is predicted to have 15 transmembrane domains (Veronico et al, 2001). Available data and comparisons with other glycosyltransferases, such as hyaluronan synthase, suggest that that these proteins may form multimers in the plasma membrane, creating a channel through which the nascent chitin is translocated across the membrane (Merzendorfer, 2006).…”