Submitted to: Insect Molecular Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/1/2006
Publication Date: 11/1/2006
Citation: Zou, Z., Lopez, D.L., Kanost, M., Evans, J.D., Jiang, H. 2006. Comparative analysis of serine protease-related genes in the honey bee genome. Insect Molecular Biology. 15:603-614. Interpretive Summary: While honey bees are firmly established as an important part of U.S. agriculture, they are often threatened by important diseases. One group of enzymes, the serine proteases, is known to have huge effects on insect health, from development to immune responses. This paper describes all of the known serine proteases in honey bees, and measures the responses of these enzymes to the important bee disease agent Paenibacillus larvae (the bacterium that causes American foulbrood disease). The results help connect a number of these enzymes to the honey bee immune response, giving fresh material for improving bee breeding and management in the face of several important diseases. The results should simplify the search for key components of honey bee immunity, giving researchers and breeders another tool in the important efforts to maintain honey bees as effective pollinators and food producers.
Technical Abstract: We have identified 44 serine protease (SP) and 13 serine protease homolog (SPH) genes in the genome of Apis mellifera. Most of these genes encode putative secreted proteins, but 4 SPs and 3 SPHs may associate with the plasma membrane via a transmembrane region. Clip domains represent the most abundant non-catalytic structural units in these SP-like proteins – 12 SPs and 6 SPHs contain at least one clip domain. Some of the family members contain other modules for protein-protein interactions, including disulfide-stabilized structures (LDLrA, SRCR, frizzled, kringle, Sushi, Wonton and Pan/apple), carbohydrate-recognition domains (C-type lectin and chitin-binding), and other modules (such as zinc finger, CUB, coiled coil and Sina). Comparison of the sequences with those from Drosophila led to a proposed SP pathway for establishing the dorsoventral axis of honey bee embryos. Multiple sequence alignments revealed evolutionary relationships of honey bee SPs and SPHs with those in D. melanogaster, Anopheles gambiae, and Manduca sexta. We identified homologs of D. melanogaster persephone, M. sexta HP14, PAP-1 and SPH-1. Quantitative RT-PCR analyses showed an elevation in the mRNA levels of SP2, SP3, SP9, SP10, SPH41, SPH42, SP49, serpin-2, serpin-4, serpin-5 and spätzle-2 in adults after a microbial challenge. The SP41 and SP6 transcripts significantly increased after an injection of Paenibacillus larva, but there was no such increase after injection of saline or Escherichia coli. mRNA levels of most SPs and serpins significantly increased by 48 h after the pathogen infection in 1st instar larvae. On the contrary, SP1, SP3, SP19 and serpin-5 transcript levels reduced. These results, taken together, provide a framework for designing experimental studies of the roles of SPs and related proteins in embryonic development and immune responses of A. mellifera.