title: Nitric oxide participates in the toxicity of Bacillus thuringiensis Cry1Ab toxin to kill Manduca sexta larvae.
abstract: Nitric oxide (NO) produced by the nitric oxide synthase (NOS) enzyme is a reactive oxygen molecule widely considered as important participant in the immune system of different organisms to confront microbial infections. In insects the NO molecule has also been implicated in immune response against microbial pathogens. Bacillus thuringiensis (Bt) is an insect-pathogenic bacterium that produces insecticidal proteins such as Cry toxins. These proteins kill insects because they form pores in the larval-midgut cells. Here we show that intoxication of Manduca sexta larvae with Cry1Ab activates expression of NOS with a corresponding increase in NO. This effect is not observed with a non-toxic mutant toxin Cry1Ab-E129K that is affected in pore formation. The increased production of NO triggered by intoxication with LC50 dose of Cry1Ab toxin is not associated with higher expression of antimicrobial peptides. NO participates in Cry1Ab toxicity since inhibition of NOS by selective l-NAME inhibitor prevented NO production and resulted in reduced mortality of the larvae. The fact that mortality was not completely abolished by L-NAME indicates that other processes participate in toxin action and induction of NO production upon Cry1Ab toxin administration accounts only for a part of the toxicity of this protein to M. sexta larvae.
authors: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico. Electronic address: ec.chavez.hdz@gmail.com.
authors: Carolina
authors: C
authors: Chavez
authors: Centro de Investigaciones Sobre Enfermedades Infecciosas, Instituto Nacional de Salud Pública, Av. Universidad 655, Cuernavaca, Morelos 62100, Mexico; Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico. Electronic address: benitort@gmail.com.
authors: Benito
authors: B
authors: Recio-Tótoro
authors: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico. Electronic address: biviana@ibt.unam.mx.
authors: Biviana
authors: B
authors: Flores-Escobar
authors: Centro de Investigaciones Sobre Enfermedades Infecciosas, Instituto Nacional de Salud Pública, Av. Universidad 655, Cuernavaca, Morelos 62100, Mexico. Electronic address: humberto@insp.mx.
authors: Humberto
authors: H
authors: Lanz-Mendoza
authors: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico. Electronic address: jsanchez@ibt.unam.mx.
authors: Jorge
authors: J
authors: Sanchez
authors: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico. Electronic address: mario@ibt.unam.mx.
authors: Mario
authors: M
authors: Soberón
authors: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico. Electronic address: bravo@ibt.unam.mx.
authors: Alejandra
authors: A
authors: Bravo
mesh_terms: D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000096:biosynthesis; D001413:Bacillus thuringiensis / Q000502:physiology*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000502:physiology*; D004731:Endotoxins / Q000502:physiology*; D006460:Hemolysin Proteins / Q000502:physiology*; D007113:Immunity, Innate; D019476:Insect Proteins / Q000378:metabolism; D018402:Manduca / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000378:metabolism
chemical_list: D023181:Antimicrobial Cationic Peptides; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D019476:Insect Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase
keywords: Bacillus thuringiensis Cry toxin; Manduca sexta; Nitric oxide