Comparisons of transcriptional profiles of gut genes between cry1Ab-resistant and susceptible strains of Ostrinia nubilalis revealed genes possibly related to the adaptation of resistant larvae to transgenic cry1Ab corn

Authors: Yao, Jianxiu; Zhu, Yu Cheng; NANYAN, LU - Kansas State University; BUSCHMAN, LAWRENT - Kansas State University; ZHU, KUN YAN - Kansas State University

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2017
Publication Date: 1/30/2017
Citation: Yao, J., Zhu, Y., Nanyan, L., Buschman, L.L., Zhu, K. 2017. Comparisons of transcriptional profiles of gut genes between cry1Ab-resistant and susceptible strains of Ostrinia nubilalis revealed genes possibly related to the adaptation of resistant larvae to transgenic cry1Ab corn. International Journal of Molecular Sciences. 18:301. doi:10.3390/ijms18020301.

Interpretive Summary: This study identified the differentially expressed European corn borer gut genes when exposed to transgenic corn expressing Cry1Ab Bt toxin. More genes changed expression levels in the S(susceptible)-strain (398 gut genes) larvae gut than in the R(resistant)-strain (264 genes). The gene expression ratios were much higher in the S-strain than in the R-strain. Even though the Cry1Ab protoxin selected R-strain larvae had a higher tolerance to transgenic corn expressed Cry1Ab toxin, they still did not survive. Their specific functions of the differentially expressed genes in Bt toxicity are worthy of further investigation. Cry toxin ingestion triggered complicated cellular signaling for survival, from sensing cell ion imbalance, defense pore formation, to repairing of cell membrane integrity etc. This study proposed that insect defense against transgenic corn expressed Cry toxin included multiple proteins involvement, from gut lumen digestion enzymes, gut cell membrane binding partners, cellular defense factors, to gut membrane integrity maintenance. Any changes in this complex could contribute to insect survival in the presence of Cry toxins. Nevertheless, further studies will be necessary to clarify the functional roles of differentially expressed genes in Cry1Ab toxicity and resistance.

Technical Abstract: European corn borer (Ostrinia nubilalis) gut 2,895 unique genes expressions were quantified and compared between a laboratory-selected Cry1Ab-resistant (R) strain and a susceptible (S) strain after fed transgenic corn (MON810) leaves expressing Cry1Ab by microarray. A total of 398 gut genes were differentially expressed in S-strain larvae, whereas only 264 gut genes were differentially expressed in R-strain larvae after fed transgenic corn leaves for six hrs. Many of these genes also showed higher ratios of differential expressions in S-strain larvae than in R-strain larvae. These results imply that R-strain larvae had an increased ability to deal with transgenic corn as compared with S-strain larvae. We also revealed that 17 and 9 significantly up- or down-regulated gut genes from S- and R-strain larvae, respectively, including serine proteases (trypsins and chymotrypsins), and aminopeptidases. They may be associated with Bt Cry toxin toxicity by degradation, binding, and cellular defense. Overall, our study may suggest an improved adaptation of Cry1Ab-resistant O. nubilalis larvae on transgenic Cry1Ab corn because the greater number and the higher expression ratios of differentially expressed gut genes could be attributed to the greater stress in S-strain larval gut when they ingested transgenic Cry1Ab corn leaves. However, further studies will be necessary to clarify functional roles of these differentially expressed gut genes in response to the ingestion of the transgenic corn leaves.