Repeated exposure of fluazinam fungicides affects gene expression profiles yet carries no costs on a nontarget pest

Abstract

Fungicides are used to control pathogenic fungi of crop species, but they have also been shown to alter behavioral, life history and fitness related traits of nontarget insects. Here, we tested the fungicide effects on feeding behavior, survival and physiology of the nontarget pest insect, the Colorado potato beetle (CPB) (Leptinotarsa decemlineata). Feeding behavior was studied by a choice test of adult beetles, which were allowed to choose between a control and a fungicide (fluazinam) treated potato leaf. Larval survival was recorded after 24 and 72 h exposure to control and fungicide‐treated leaves with 2 different concentrations. The adults did not show fungicide avoidance behavior. Similarly, survival of the larvae was not affected by the exposure to fungicides. Finally, to understand the effects of fungicides at the physiological level (gene expression), we tested whether the larval exposure to fungicide alter the expression of 5 metabolic pathway and stress associated genes. Highest concentration and 72‐h exposure caused upregulation of 1 cytochrome P450 (CYP9Z14v2) and 1 insecticide resistance gene (Ldace1), whereas metabolic detoxification gene (Ugt1) was downregulated. At 24‐h exposure, highest concentration caused downregulation of another common detoxification gene (Gs), while both exposure times to lowest concentration caused upregulation of the Hsp70 stress tolerance gene. Despite these overall effects, there was a considerable amount of variation among different families in the gene expression levels. Even though the behavioral effects of the fungicide treatments were minor, the expression level differences of the studied genes indicate changes on the metabolic detoxifications and stress‐related pathways.

Leveraging RNA Interference to Impact Insecticide Resistance in the Colorado Potato Beetle, Leptinotarsa decemlineata

“…It is interesting to note that parallel work identified structural variants in CYP4g15 as notably exemplified by the significant number of single nucleotide polymorphism outliers associated with this target and suggested a potential contribution of this candidate cytochrome P450 in insecticide resistance [ 37 ]. Work aimed at characterizing the molecular impact of fluazinam showed elevated levels of CYP9Z14v2 transcripts in L. decemlineata larvae exposed to the highest concentration investigated [ 38 ]. An overview of studies that investigated the differential expression of cytochrome P450s in L. decemlineata that were treated to insecticides or that were confirmed resistant to a given compound is shown in Table 1 .…”