Transcriptomic responses in ham mite (Tyrophagus putrescentiae) to propylene glycol exposure

Tyrophagus putrescentiae, commonly referred to as the ham or cheese mite, are tiny arachnid pests that infest dry-cured hams and aged cheeses. Previous studies have indicated that propylene glycol (PG) is a safe and effective treatment for control of ham mite infestations in laboratory-scale experiments. Mixed-sex mites were inoculated on ham cubes that were dipped in PG (n = 6), while untreated ham cubes served as the control (n = 6). After incubation for 72 h at 25 ± 2° C and 70 ± 5% RH, mites from each treatment group were pooled and RNA-seq was used to characterize mite transcriptomes and check for differences in gene expression. Out of 19,199 annotated genes, approximately 64% were functionally annotated. In total, 649 genes were differentially expressed (p < 0.05, log2 fold change < - 1 or > 1) due to PG exposure, with 74 genes upregulated and 575 downregulated. Functional enrichment analysis revealed that there were 14 pathways and 21 gene ontology (GO) terms significantly over-represented in the differentially expressed genes, indicating that PG exposure affects genes involved in degradation, detoxification, glycolysis, and gluconeogenesis, and suggests that ham mites are deterred by PG, resulting in starvation and the mite's eventual death. However, the toxicity of PG from consumption has not yet been proven and requires further experimentation.