title: Sequence variation and differential splicing of the midgut cadherin gene in Trichoplusia ni.
abstract: The insect midgut cadherin serves as an important receptor for the Cry toxins from Bacillus thuringiensis (Bt). Variation of the cadherin in insect populations provides a genetic potential for development of cadherin-based Bt resistance in insect populations. Sequence analysis of the cadherin from the cabbage looper, Trichoplusia ni, together with cadherins from 18 other lepidopterans showed a similar phylogenetic relationship of the cadherins to the phylogeny of Lepidoptera. The midgut cadherin in three laboratory populations of T. ni exhibited high variability, although the resistance to Bt toxin Cry1Ac in the T. ni strain is not genetically associated with cadherin gene mutations. A total of 142 single nucleotide polymorphisms (SNPs) were identified in the cadherin cDNAs from the T. ni strains, including 20 missense mutations. In addition, insertion and deletion polymorphisms (indels) were also identified in the cadherin alleles in T. ni. More interestingly, the results from this study reveal that differential splicing of mRNA also occurs in the cadherin gene expression. Therefore, variation of the midgut cadherin in insects may not only be caused by cadherin gene mutations, but could also result from alternative splicing of its mRNA regulated by factors acting in trans. Analysis of cadherin gene alleles in F2, F3 and F4 progenies from the cross between the Cry1Ac resistant and the susceptible strain after consecutive selections with Cry1Ac for three generations showed that selection with Cry1Ac did not result in an increase of frequencies of the cadherin alleles originated from the resistant strain.
authors.affiliation: Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.forename: Wendy
authors.initials: W
authors.lastname: Kain
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
mesh_terms: D000483:Alleles; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001483:Base Sequence; D015820:Cadherins / Q000235:genetics* / Q000378:metabolism; D003433:Crosses, Genetic; D018076:DNA, Complementary / Q000737:chemistry; D004731:Endotoxins; D041981:Gastrointestinal Tract / Q000378:metabolism; D006460:Hemolysin Proteins; D054643:INDEL Mutation; D019476:Insect Proteins / Q000235:genetics* / Q000378:metabolism; D007305:Insecticide Resistance / Q000235:genetics; D008969:Molecular Sequence Data; D009036:Moths / Q000235:genetics* / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D017422:Sequence Analysis, DNA
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D015820:Cadherins; D018076:DNA, Complementary; D004731:Endotoxins; D006460:Hemolysin Proteins; D019476:Insect Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis
keywords: Bt resistance; Cadherin; Midgut; Trichoplusia ni