title: Down regulation of a gene for cadherin, but not alkaline phosphatase, associated with Cry1Ab resistance in the sugarcane borer Diatraea saccharalis.
abstract: The sugarcane borer, Diatraea saccharalis, is a major target pest of transgenic corn expressing Bacillus thuringiensis (Bt) proteins (i.e., Cry1Ab) in South America and the mid-southern region of the United States. Evolution of insecticide resistance in such target pests is a major threat to the durability of transgenic Bt crops. Understanding the pests' resistance mechanisms will facilitate development of effective strategies for delaying or countering resistance. Alterations in expression of cadherin- and alkaline phosphatase (ALP) have been associated with Bt resistance in several species of pest insects. In this study, neither the activity nor gene regulation of ALP was associated with Cry1Ab resistance in D. saccharalis. Total ALP enzymatic activity was similar between Cry1Ab-susceptible (Cry1Ab-SS) and -resistant (Cry1Ab-RR) strains of D. saccharalis. In addition, expression levels of three ALP genes were also similar between Cry1Ab-SS and -RR, and cDNA sequences did not differ between susceptible and resistant larvae. In contrast, altered expression of a midgut cadherin (DsCAD1) was associated with the Cry1Ab resistance. Whereas cDNA sequences of DsCAD1 were identical between the two strains, the transcript abundance of DsCAD1 was significantly lower in Cry1Ab-RR. To verify the involvement of DsCAD1 in susceptibility to Cry1Ab, RNA interference (RNAi) was employed to knock-down DsCAD1 expression in the susceptible larvae. Down-regulation of DsCAD1 expression by RNAi was functionally correlated with a decrease in Cry1Ab susceptibility. These results suggest that down-regulation of DsCAD1 is associated with resistance to Cry1Ab in D. saccharalis.
authors: Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, United States of America.
authors: Yunlong
authors: Y
authors: Yang
authors: Yu Cheng
authors: YC
authors: Zhu
authors: James
authors: J
authors: Ottea
authors: Claudia
authors: C
authors: Husseneder
authors: B Rogers
authors: BR
authors: Leonard
authors: Craig
authors: C
authors: Abel
authors: Randall
authors: R
authors: Luttrell
authors: Fangneng
authors: F
authors: Huang
mesh_terms: D000469:Alkaline Phosphatase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000633:toxicity*; D015820:Cadherins / Q000235:genetics* / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D004064:Digestive System / Q000187:drug effects / Q000201:enzymology; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics*; D004731:Endotoxins / Q000633:toxicity*; D017344:Genes, Insect / Q000235:genetics*; D006460:Hemolysin Proteins / Q000633:toxicity*; D007305:Insecticide Resistance / Q000187:drug effects* / Q000235:genetics; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007814:Larva / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D008969:Molecular Sequence Data; D009036:Moths / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D010802:Phylogeny; D034622:RNA Interference / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D031786:Saccharum / Q000469:parasitology; D016415:Sequence Alignment; D016019:Survival Analysis
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D015820:Cadherins; D018076:DNA, Complementary; D004731:Endotoxins; D006460:Hemolysin Proteins; D007527:Isoenzymes; D012333:RNA, Messenger; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D000469:Alkaline Phosphatase