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United States Department of Agriculture

Agricultural Research Service

Title: Characterization of a Honey Bee Toll Related Receptor Gene Aw18w and Its Potential Involvement in Antimicrobial Immune Defense

Authors
item Aronstein, Katherine
item Saldivar, Eduardo

Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 14, 2004
Publication Date: January 10, 2005
Citation: Aronstein, K.A., Saldivar, E. 2005. Characterization of a honey bee Toll related receptor gene Am18w and its potential involvement in antimicrobial immune defense. Apidologie. 36(1):3-14.

Interpretive Summary: Host defense against various micro-organisms involves different recognition and signaling pathways. These signaling pathways regulate expression of antimicrobial peptides that are active against Gram-positive and Gram-negative bacteria, as well as fungi. Toll receptors are involved in the intracellular signal transduction and initiation of insect antimicrobial immune responses. Here we report the isolation and characterization of a novel gene from honey bee Apis mellifera, which encodes for the Toll-like receptor. The sequence analysis of the deduced protein sequence revealed a conserved intracellular signaling domain characteristic of signal transducing receptors found not only in insects but also in vertebrates. This similarity of honey bee Toll-like gene suggests possible involvement of honey bee Am18w in host immune responses and subsequent activation of the antimicrobial peptide genes. The expression profiles of the honey bee Toll-like receptor gene Am18w were examined in all developmental stages, before and after immune challenge. Here we demonstrate that injection of dsRNA probe into honey bee larvae successfully disrupts the endogenous mRNA of the target gene and allows us to examine the effects of Am18w gene silencing (RNAi) on the expression level of the antimicrobial peptides.

Technical Abstract: Toll receptors are involved in the intracellular signal transduction and initiation of insect antimicrobial immune responses. They are characterized by the presence of repeated copies of (LRR) leucine-rich motif within receptor extracellular domain and (TIR) signaling domain homologous to the cytoplasmic domain of the interleukin 1 receptor. Here we report the isolation and characterization of a novel gene (Am18w) from honey bee Apis mellifera, which encodes for the Toll-like receptor and shares a striking 51.4 % with Bombyx mori 18-wheeler, 46.6 % identity with Drosophila Toll-7 receptor and 42.5 % with Drosophila 18-wheeler. The sequence analysis of the deduced 18W protein revealed a conserved (TIR) intracellular signaling domain characteristic of signal transducing receptors found in Toll and mammalian interleukin 1 (IL-1) receptors. This similarity of a honey bee Toll-related receptor to signal transducing receptors suggests possible involvement of honey bee Am18w in host immune responses and subsequent activation of the antimicrobial peptide genes. The expression profiles of the honey bee Toll-like receptor gene Am18w were examined in all developmental stages, before and after immune challenge. Here we demonstrate that injection of dsRNA probe into honey bee larvae successfully disrupts the endogenous mRNA of the target gene and allows us to examine the effects of Am18w gene silencing (RNAi) on the expression level of the antimicrobial peptides.

Last Modified: 11/23/2014