The Caenorhabditis elegans CUB-like-domain containing protein RBT-1 functions as a receptor for Bacillus thuringiensis Cry6Aa toxin

Abstract

Plant-parasitic nematodes cause huge agricultural economic losses. Two major families of Bacillus thuringiensis crystal proteins, Cry5 and Cry6, show nematicidal activity. Previous work showed that binding to midgut receptors is a limiting step in Cry toxin mode of action. In the case of Cry5Ba, certain Caenorhabditis elegans glycolipids were identified as receptors of this toxin. However, the receptors for Cry6 toxin remain unknown. In this study, the C. elegans CUB-like-domain containing protein RBT-1, released by phosphatidylinositol-specific phospholipase C (PI-PLC), was identified as a Cry6Aa binding protein by affinity chromatography. RBT-1 contained a predicted glycosylphosphatidylinositol (GPI) anchor site and was shown to locate in lipid rafts in the surface of the midgut cells. Western ligand blot assays and ELISA binding analysis confirmed the binding interaction between Cry6Aa and RBT-1 showing high affinity and specificity. In addition, the mutation of rbt-1 gene decreased the susceptibility of C. elegans to Cry6Aa but not that of Cry5Ba. Furthermore, RBT-1 mediated the uptake of Cry6Aa into C. elegans gut cells, and was shown to be involved in triggering pore-formation activity, indicating that RBT-1 is required for the interaction of Cry6Aa with the nematode midgut cells. These results support that RBT-1 is a functional receptor for Cry6Aa.

Systemic mitochondrial disruption is a key event in the toxicity of bacterial pore‐forming toxins to Caenorhabditis elegans

“…Synchronized L4 worms were used for the lethal assay according to the reported procedures (Barrows et al ., 2006; Shi et al ., 2020). All bioassays were conducted in M9 buffer (2.2 mM KH 2 PO 4 , 4.2 mM Na 2 HPO 4 , 85.6 mM NaCl, 1 mM MgSO 4 ) containing OP50 as food.…”

Toxicity of Bacillus thuringiensis Strains Derived from the Novel Crystal Protein Cry31Aa with High Nematicidal Activity against Rice Parasitic Nematode Aphelenchoides besseyi

“…Furthermore, the beneficial properties of Bt strains are not limited to their biological control activity; however, a variety of endophytes possess the ability to indirectly or directly promote plant growth and development [ 27 , 28 ]. Bt is one of the most important phosphate-dissolving bacteria [ 29 ], which can be insoluble in the soil through enzymatic activity.…”

Characterization of Nematicidal Activity and Nematode-Toxic Metabolites of a Soilborne Brevundimonas bullata Isolate

“…These bacteria include Bacillus subtilis [11], Bacillus thuringiensis [12,13], Bacillus amyloliquefaciens [14], Bacillus cereus [15], Bacillus firmus [16][17][18], Bacillus nematocida [19], Pseudomonas aeruginosa [20][21][22], Pseudomonas putida [23], Pseudomonas simiae [24], Pseudomonas syringae [25][26][27], Burkholderia cepacia [28], Streptomyces avermitilis [29,30], and Pasteuria penetrans [31]. These nematicidal bacteria affect the target nematodes through different mechanisms, such as restraining the growth and reproduction of nematodes and direct pathogenesis, which are carried out by the production of toxic proteins [32,33], enzymes [12,26,34], small-molecule metabolites [23,24,35], or invasive parasitization [36,37]. In this respect, bacterial nematicides have shown particular usefulness in terms of their relatively high specificity, their ability to act on the underground parts of plants, and the difficulty in resistance-development in nematodes.…”