title: Resistance to Bacillus thuringiensis Toxin Cry2Ab in Trichoplusia ni Is Conferred by a Novel Genetic Mechanism.
abstract: The resistance to the Bacillus thuringiensis (Bt) toxin Cry2Ab in a greenhouse-originated Trichoplusia ni strain resistant to both Bt toxins Cry1Ac and Cry2Ab was characterized. Biological assays determined that the Cry2Ab resistance in the T. ni strain was a monogenic recessive trait independent of Cry1Ac resistance, and there existed no significant cross-resistance between Cry1Ac and Cry2Ab in T. ni. From the dual-toxin-resistant T. ni strain, a strain resistant to Cry2Ab only was isolated, and the Cry2Ab resistance trait was introgressed into a susceptible laboratory strain to facilitate comparative analysis of the Cry2Ab resistance with the susceptible T. ni strain. Results from biochemical analysis showed no significant difference between the Cry2Ab-resistant and -susceptible T. ni larvae in midgut proteases, including caseinolytic proteolytic activity and zymogram profile and serine protease activities, in midgut aminopeptidase and alkaline phosphatase activity, and in midgut esterases and hemolymph plasma melanization activity. For analysis of genetic linkage of Cry2Ab resistance with potential Cry toxin receptor genes, molecular markers for the midgut cadherin, alkaline phosphatase (ALP), and aminopeptidase N (APN) genes were identified between the original greenhouse-derived dual-toxin-resistant and the susceptible laboratory T. ni strains. Genetic linkage analysis showed that the Cry2Ab resistance in T. ni was not genetically associated with the midgut genes coding for the cadherin, ALP, and 6 APNs (APN1 to APN6) nor associated with the ABC transporter gene ABCC2. Therefore, the Cry2Ab resistance in T. ni is conferred by a novel but unknown genetic mechanism.
authors.affiliation: Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, New York, USA.
authors.forename: Xiaozhao
authors.initials: X
authors.lastname: Song
authors.affiliation: Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, New York, USA.
authors.forename: Wendy
authors.initials: W
authors.lastname: Kain
authors.affiliation: Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, New York, USA.
authors.forename: Douglas
authors.initials: D
authors.lastname: Cassidy
authors.affiliation: Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, New York, USA pw15@cornell.edu.
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
mesh_terms: D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000633:toxicity*; D003433:Crosses, Genetic; D004731:Endotoxins / Q000633:toxicity*; D008040:Genetic Linkage; D006460:Hemolysin Proteins / Q000633:toxicity*; D007305:Insecticide Resistance; D007306:Insecticides / Q000633:toxicity*; D007814:Larva / Q000187:drug effects; D007915:Lepidoptera / Q000187:drug effects* / Q000235:genetics*
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis