Microarray analysis of global gene regulation in the Cry1Ab-resistant and Cry1Ab-susceptible strains of Diatraea saccharalis.
BACKGROUND
Extensive adoption of transgenic Bt corn in recent years for stalk borer control has increased risk of resistance evolution in the target pest populations. A Bt-resistant strain of the sugarcane borer, Diatraea saccharalis, was approximately 100-fold more tolerant to Cry1Ab toxin than the susceptible counterpart. To gain a better understanding of the molecular mechanisms of Bt resistance, the Cry1Ab-susceptible (Cry1Ab-SS) and Cry1Ab-resistant (Cry1Ab-RR) strains of D. saccharalis were subjected to a microarray analysis.


RESULTS
Results showed that the expression levels of many genes were significantly different between the Cry1Ab-RR and Cry1Ab-SS strains. Microarray analysis of 7145 cDNAs revealed 384 differentially expressed genes. A total of 273 genes were significantly upregulated 2-51.6-fold, and 111 genes were significantly downregulated 2-22.6-fold in the Cry1Ab-RR strain. The upregulation of three potential resistance-related genes, coding for a glutathione S-transferase (GST), a chymotrypsin-like protease (CHY) and a lipase (LP), was confirmed using real-time PCR, indicating a reproducibility of the microarray data. Ontology analysis revealed that more than twice the number of metabolic-related genes were upregulated compared with downregulated genes with the same biological function. Up to 35.2% of the upregulated genes in the resistant strain were associated with catalytic activity, while only 9.5% of the downregulated genes were related to the same catalytic molecular function.


CONCLUSIONS
The large portion of metabolic- or catalytic-related genes with significant upregulations indicated a potential large increase in metabolic or catalytic activities in the Cry1Ab-RR strain. This cDNA microarray gene expression data could be used to characterize and identify new genes that may be associated with Bt resistance in D. saccharalis.
SIMRU, ARS-USDA, Stoneville, MS, USA.
Zibiao
Z
Guo
Yu
Y
Cheng Zhu
Fangneng
F
Huang
Randall
R
Luttrell
Rogers
R
Leonard
D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000494:pharmacology*; D004731:Endotoxins / Q000494:pharmacology*; D005786:Gene Expression Regulation; D006460:Hemolysin Proteins / Q000494:pharmacology*; D019476:Insect Proteins / Q000235:genetics* / Q000378:metabolism; D007305:Insecticide Resistance; D008969:Molecular Sequence Data; D009036:Moths / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D019476:Insect Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis