Resistance to Bacillus thuringiensis Toxin in Caenorhabditis elegans from Loss of Fucose

Abstract

A mutation in the Caenorhabditis elegans bre-1 gene was isolated in a screen for Bacillus thuringiensis toxin-resistant (bre) mutants to the Cry5B crystal toxin made by B. thuringiensis. bre-1 mutant animals are different from the four other cloned bre mutants in that their level of resistance is noticeably lower. bre-1 animals also display a significantly reduced brood size at 25°C. Here we cloned the bre-1 gene and characterized the bre-1 mutant phenotype. bre-1 encodes a protein with significant homology to a GDP-mannose 4,6-dehydratase, which catalyzes the first step in the biosynthesis of GDP-fucose from GDP-mannose. Injection of GDP-fucose but not fucose into C. elegans intestinal cells rescues bre-1 mutant phenotypes. Thus, C. elegans lacks a functional fucose salvage pathway. Furthermore, we demonstrate that bre-1 mutant animals are defective in production of fucosylated glycolipids and that bre-1 mutant animals make quantitatively reduced levels of glycolipid receptors for Cry5B. We finally show that bre-1 mutant animals, although viable, show a lack of fucosylated N-and O-glycans, based on mass spectrometric evidence. Thus, C. elegans can survive with little fucose and can develop resistance to crystal toxin by loss of a monosaccharide biosynthetic pathway.The crystal (Cry) 3 proteins made by Bacillus thuringiensis are naturally occurring agents that are used for the control of insects that eat crops and carry disease (1). Cry proteins have been used for over 50 years as an environmentally safe and effective alternative to synthetic pesticides. One attractive feature of Cry proteins is their nontoxicity toward mammals and other vertebrates (2). Consistent with this lack of mammalian toxicity, several of the receptors for Cry proteins have been characterized and encode invertebrate-specific glycolipids and/or an insect family of cadherins (3). Because of their efficacy against invertebrates and safety toward vertebrates, Cry proteins are widely used worldwide as topical sprays on crops, as topical sprays to kill mosquitoes and black flies that carry disease, and as transgenes expressed in plants as an environmentally friendly alternative to chemical pesticides (4,5). In the year 2005, over 26 million hectares of B. thuringiensis transgenic corn and cotton were planted (6). In addition, B. thuringiensis crystal proteins are now also being explored for their possible use in the control of nematode parasites (7,8).In our efforts to gain insight into the important question of how invertebrates develop resistance to Cry proteins, we isolated mutations in five Caenorhabditis elegans genes that result in resistance to the crystal protein, Cry5B (9). Four of these bre genes have been cloned and characterized. These genes, bre-2, bre-3, bre-4, and bre-5, encode glycosyltransferase genes that catalyze the addition of monosaccharides onto invertebratespecific glycolipids (10 -12). The resulting oligosaccharide chain is a receptor for the Cry protein (11). Thus, loss of any one of these genes results in loss of t...

Dissimilar Crystal Proteins Cry5Ca1 and Cry5Da1 Synergistically Act against Meloidogyne incognita and Delay Cry5Ba-Based Nematode Resistance

“…Cry5Da also exhibited increased inhibition compared to that of Cry5Ca but decreased inhibition compared to that of Cry5Ba. It has been previously mentioned that nematode fertility is also deemed a judgment criterion (27). Therefore, a brood size inhibition assay was performed, and it was found that Cry5 toxins affected offspring birth rates.…”

The Caenorhabditis elegansbus-2 Mutant Reveals a New Class of O-Glycans Affecting Bacterial Resistance

“…The bus-2 O-Glycosylation Profile Is Altered-Ce core-1 glycans have been previously described (15,27,33,34). Permethylation renders the response of glycomers in a related series to be nearly identical with respect to detection by mass spectrometry and, thus, enables reproducible and semiquantitative compar-ison of biologically related samples (19).…”

Multiple reciprocal adaptations and rapid genetic change upon experimental coevolution of an animal host and its microbial parasite

“…For this purpose, we established a model of experimental host-parasite coevolution based on a multicellular host, the nematode Caenorhabditis elegans, and a microbial parasite, the Gram-positive bacterium Bacillus thuringiensis. Both antagonists show specific adaptations to each other, including the involvement of a characteristic set of host defense genes and a toxin-mediated process of persistent infection and host killing that is required for bacterial transmission (26)(27)(28)(29)(30)(31)(32).…”