title: PC, a Novel Oral Insecticidal Toxin from Bacillus bombysepticus Involved in Host Lethality via APN and BtR-175.
abstract: Insect pests have developed resistance to chemical insecticides, insecticidal toxins as bioinsecticides or genetic protection built into crops. Consequently, novel, orally active insecticidal toxins would be valuable biological alternatives for pest control. Here, we identified a novel insecticidal toxin, parasporal crystal toxin (PC), from Bacillus bombysepticus (Bb). PC shows oral pathogenic activity and lethality towards silkworms and Cry1Ac-resistant Helicoverpa armigera strains. In vitro assays, PC after activated by trypsin binds to BmAPN4 and BtR-175 by interacting with CR7 and CR12 fragments. Additionally, trypsin-activated PC demonstrates cytotoxicity against Sf9 cells expressing BmAPN4, revealing that BmAPN4 serves as a functional receptor that participates in Bb and PC pathogenicity. In vivo assay, knocking out BtR-175 increased the resistance of silkworms to PC. These data suggest that PC is the first protein with insecticidal activity identified in Bb that is capable of causing silkworm death via receptor interactions, representing an important advance in our understanding of the toxicity of Bb and the contributions of interactions between microbial pathogens and insects to disease pathology. Furthermore, the potency of PC as an insecticidal protein makes it a good candidate for inclusion in integrated agricultural pest management systems.
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Lin
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Tingcai
authors.initials: T
authors.lastname: Cheng
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Shengkai
authors.initials: S
authors.lastname: Jin
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Yuqian
authors.initials: Y
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Bohua
authors.initials: B
authors.lastname: Fu
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Renwen
authors.initials: R
authors.lastname: Long
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Qingyou
authors.initials: Q
authors.lastname: Xia
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001407:Bacillus / Q000737:chemistry*; D001427:Bacterial Toxins / Q000008:administration & dosage / Q000633:toxicity*; D012831:Bombyx / Q000187:drug effects / Q000254:growth & development; D007306:Insecticides / Q000008:administration & dosage / Q000633:toxicity*; D007814:Larva / Q000254:growth & development; D010572:Pest Control, Biological
chemical_list: D001427:Bacterial Toxins; D007306:Insecticides