Genetic mapping of Bt-toxin binding proteins in a Cry1A-toxin resistant strain of diamondback moth Plutella xylostella.
A major mechanism of resistance to Bacillus thuringiensis (Bt) toxins in Lepidoptera is a reduction of toxin binding to sites in the midgut membrane. Genetic studies of three different species have shown that mutations in a candidate Bt receptor, a 12-cadherin-domain protein, confer Cry1A toxin resistance. Despite a similar resistance profile in a fourth lepidopteran species, Plutella xylostella, we have previously shown that the cadherin orthologue maps to a different linkage group (LG8) than Cry1Ac resistance (LG22). Here we tested the hypothesis that mutations in other genes encoding candidate Bt-binding targets could be responsible for Bt resistance, by mapping eight aminopeptidases, an alkaline phosphatase (ALP), an intestinal mucin, and a P252 glycoprotein with respect to the 29 AFLP marked linkage groups in a P. xylostella cross segregating for Cry1Ac resistance. A homologue of the Caenorhabditis elegans Bt resistance gene bre-2 was also mapped. None of the genes analysed were on the same chromosome containing the Cry1Ac resistance locus, eliminating them as candidate resistance genes in the parental resistant strain SC1. Although this finding excludes cis-acting mutations in these genes as causing resistance in this strain, one or more of the expressed proteins may still bind Cry1Ac toxin, and post-translational modifications could affect this binding and thereby exert a trans-acting effect on resistance.
Baxter
Simon W
SW
CESAR, Department of Genetics, University of Melbourne, Parkville, Vic. 3010, Australia. swb29@cam.ac.uk
Zhao
Jian-Zhou
JZ
Shelton
Anthony M
AM
Vogel
Heiko
H
Heckel
David G
DG
D000469:Alkaline Phosphatase / Q000378:metabolism; D000595:Amino Acid Sequence; D054458:Amplified Fragment Length Polymorphism Analysis; D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000378:metabolism*; D001427:Bacterial Toxins / Q000378:metabolism*; D018826:CD13 Antigens / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002874:Chromosome Mapping; D004731:Endotoxins / Q000378:metabolism*; D005260:Female; D008040:Genetic Linkage; D006460:Hemolysin Proteins / Q000378:metabolism*; D019476:Insect Proteins / Q000235:genetics* / Q000378:metabolism; D007305:Insecticide Resistance / Q000235:genetics; D007413:Intestinal Mucosa / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D009036:Moths / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D009077:Mucins / Q000378:metabolism
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D002352:Carrier Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D019476:Insect Proteins; D009077:Mucins; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D000469:Alkaline Phosphatase; D018826:CD13 Antigens