title: Tobacco plants expressing the Cry1AbMod toxin suppress tolerance to Cry1Ab toxin of Manduca sexta cadherin-silenced larvae.
abstract: Cry toxins produced by Bacillus thuringiensis bacteria are insecticidal proteins used worldwide in the control of different insect pests. Alterations in toxin-receptor interaction represent the most common mechanism to induce resistance to Cry toxins in lepidopteran insects. Cry toxins bind with high affinity to the cadherin protein present in the midgut cells and this interaction facilitates the proteolytic removal of helix α-1 and pre-pore oligomer formation. Resistance to Cry toxins has been linked with mutations in the cadherin gene. One strategy effective to overcome larval resistance to Cry1A toxins is the production of Cry1AMod toxins that lack helix α-1. Cry1AMod are able to form oligomeric structures without binding to cadherin receptor and were shown to be toxic to cadherin-silenced Manduca sexta larvae and Pectinophora gossypiella strain with resistance linked to mutations in a cadherin gene. We developed Cry1AbMod tobacco transgenic plants to analyze if Cry1AMod toxins can be expressed in transgenic crops, do not affect plant development and are able to control insect pests. Our results show that production of the Cry1AbMod toxin in transgenic plants does not affect plant development, since these plants exhibited healthy growth, produced abundant seeds, and were virtually undistinguishable from control plants. Most importantly, Cry1AbMod protein produced in tobacco plants retains its functional toxic activity against susceptible and tolerant M. sexta larvae due to the silencing of cadherin receptor by RNAi. These results suggest that CryMod toxins could potentially be expressed in other transgenic crops to protect them against both toxin-susceptible and resistant lepidopteran larvae affected in cadherin gene.
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca, Morelos 62250, Mexico. helena@ibt.unam.mx
authors.forename: Helena
authors.initials: H
authors.lastname: Porta
authors.forename: Gladys
authors.initials: G
authors.lastname: Jiménez
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Cordoba
authors.forename: Patricia
authors.initials: P
authors.lastname: León
authors.forename: Mario
authors.initials: M
authors.lastname: Soberón
authors.forename: Alejandra
authors.initials: A
authors.lastname: Bravo
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000737:chemistry / Q000235:genetics; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D015820:Cadherins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004731:Endotoxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D015870:Gene Expression; D020868:Gene Silencing; D005813:Genes, Synthetic; D006460:Hemolysin Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D007306:Insecticides / Q000378:metabolism / Q000633:toxicity; D007814:Larva / Q000187:drug effects* / Q000502:physiology; D018402:Manduca / Q000187:drug effects* / Q000502:physiology; D009154:Mutation; D010572:Pest Control, Biological / Q000379:methods*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000633:toxicity*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism / Q000633:toxicity*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D034741:RNA, Small Interfering / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism / Q000633:toxicity*
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D015820:Cadherins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; D034741:RNA, Small Interfering; C030956:insecticidal crystal protein, Bacillus Thuringiensis