Transcriptomic analyses of different Tetranychus urticae strains that differ in their resistance to the acaricide pyflubumide. Transcriptomic analyses of different Tetranychus urticae strains that differ in their resistance to the acaricide pyflubumide

No major transcriptomic differences were observed between JPR-R1/2 and JPR when strains were not exposed to pyflubumide. Only three genes (tetur13g01730, tetur14g03160, and tetur14g01700) were consistently up-regulated in JPR-R1/2, but none coded for enzymes that are known to be associated with xenobiotic metabolism. As a next step, we used the original and susceptible JPO strain, the parent of JPR, as a reference to investigate transcriptomic changes. Compared to JPO, 16 cytochrome P450s were up-regulated in JPR, whereas two CCE genes were down-regulated. In both JPR-R1/2, 13 cytochrome P450s were up-regulated compared to JPO, of which 11 genes already showed significant up-regulation in JPR (CYP392D2, CYP392D6, and CYP392E8 had the highest average transcriptional increase). As only limited constitutive gene expression differences were observed between JPR and the JPR-R1/2 strains, the plastic, environmentally dependent, transcriptomic changes were characterized to shed light on the molecular basis of pyflubumide resistance. After nine hours of exposure to a non-lethal dose of pyflubumide (100 mg/L), no DEGs were detected in JPR-R1 upon pyflubumide exposure, whereas only a single DEG (tetur04g04350, log2FC of 1.17) was observed in JPR. After 24 hours of exposure to pyflubumide (100mg/L), large transcriptomic responses were observed in JPR-R1/2. Eight cytochrome P450s were part of the positively correlated response, of which five (CYP385C4, CYP385C4v2, CYP392D2, CYP392E8, and CYP392A4) showed up-regulation after exposure to pyflubumide. Overall design: Three major experimental set-ups were performed and differed in the exposure of T. urticae strains to pyflubumide. The studied strains were: JPO, JPR, JPR-R1, and JPR-R2. JPO is the parental, sensitive strain. JPR, JPR-R1, and JPR-R2 are all resistant to pyflubumide. First, four replicates were collected from JPO, JPR, JPR-R1, and JPR-R2 that were maintained for one generation on non-sprayed plants. Second, four replicates were collected from JPR and JPR-R1 that were either exposed to pyflubumide (100 mg/L) or water for 9h. Third, four replicates were collected from JPR-R1 and JPR-R2 that were either sprayed with pyflubumide (100 mg/L) or water 24 h before collection.