Genes related to mitochondrial functions are differentially expressed in phosphine-resistant and -susceptible Tribolium castaneum

Authors: Oppert, Brenda; GUEDES, RAUL N.C. - Universidade Federal De Vicosa; AIKINS, MICHAEL - Kansas State University; Perkin, Lindsey; CHEN, ZHAORIGETU - Kansas State University; PHILLIPS, THOMAS - Kansas State University; ZHU, KUN YAN - Kansas State University; OPIT, GEORGE - Oklahoma State University; HOON, KELLY - Life Technologies Corporation; SUN, YONGMING - Life Technologies Corporation; MEREDITH, GAVIN - Life Technologies Corporation; BRAMLETT, KELLI - Life Technologies Corporation; SUPUNPONG-HERNANDEZ, NATALIE - Life Technologies Corporation; SANDERSON, BRIAN - Life Technologies Corporation; TAYLOR, MADISON - Life Technologies Corporation; DHINGRA, DALIA - Life Technologies Corporation; BLAKEY, BRANDON - Life Technologies Corporation; LORENZEN, MARCE - North Carolina State University; ADEDIPE, FOLUKEMI - North Carolina State University; Arthur, Franklin

Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2015
Publication Date: 11/18/2015
Citation: Oppert, B.S., Guedes, R., Aikins, M.J., Perkin, L.C., Chen, Z., Phillips, T.W., Zhu, K., Opit, G.P., Hoon, K., Sun, Y., Meredith, G., Bramlett, K., Supunpong-Hernandez, N., Sanderson, B., Taylor, M.W., Dhingra, D., Blakey, B., Lorenzen, M., Adedipe, F., Arthur, F.H. 2015. Genes related to mitochondrial functions are differentially expressed in phosphine-resistant and -susceptible Tribolium castaneum. BMC Genomics. 16:968. doi: 10.1186/s12864-015-2121-0.

Interpretive Summary: Phosphine is the most popular and economical fumigant, but insect resistance to phosphine is increasing. We studied the genetic differences in a phosphine-resistant strain of the red flour beetle from Brazil and compared it to a phosphine-susceptible laboratory strain. We found differences in expression levels of 53 genes in the resistant strain. However, reducing expression of the most highly expressed gene, a cytochrome P450, in the resistant strain did not prevent resistance. We also tried to mimic the resistant strain by reducing expression of another gene in the susceptible strain, but they were still susceptible to phosphine. We studied a known phosphine resistance gene and found mutations associated with phosphine resistance in the resistant strain. The phosphine-resistant strain was cross-resistant to a pyrethroid, suggesting that multiple resistance genes may be accumulating in stored product insects with increased insecticide exposure. These data provide valuable insights into phosphine resistance and how management strategies may need to be adjusted to maintain efficacy of insecticides.

Technical Abstract: Phosphine is a valuable fumigant to control pest populations in stored grains and grain products. However, recent studies indicate a substantial increase in phosphine resistance in major stored-cereal pests worldwide. To understand the molecular bases of phosphine resistance in insects, we used RNA-Seq to compare gene expression in a phosphine-resistant population of red flour beetle, Tribolium castaneum, to a susceptible laboratory population. Each population was evaluated (phosphine exposure or no phosphine) in triplicate biological replicates (12 samples total). Analysis of the data indicated that 53 genes were differentially expressed at a statistically significant level (p<0.01, F-test, ANOVA). In phosphine-resistant insects, eight different cytochrome P450 (CYP) genes were increased (10- to 50-fold) in expression, mainly those from the CYP6 and CYP9 subfamilies that are notorious for involvement in insecticide resistance, and seven of which increased with phosphine exposure. RNA interference (RNAi) and a CYP enzyme inhibitor were used in resistant insects to validate the role of increased CYP activity in phosphine resistance, but neither method reduced resistance. However, phosphine-resistant adults were also resistant to knockdown by the pyrethroid deltamethrin. We also found decreased expression (32- to 56-fold) in a gene related to a plant pathogenesis-related protein, but knockdown of gene expression in the susceptible strain did not induce resistance. Sequence polymorphism was found in a phosphine resistance gene, dihydrolipoamide dehydrogenase (DLD) in both susceptible and resistant insects, and a resistance marker for phosphine was found in DLD sequences from resistant insects. These data provide the first gene expression data on T. castaneum response to phopshine exposure, and demonstrate that RNA-Seq is a valuable tool to examine differences in insects that respond differentially to environmental stimuli.