D3354: Temperature changes contribute to variations in levels of transcripts with relevance to small non-coding RNAs in the Colorado potato beetle

The Colorado potato beetle, Leptinotarsa decemlineata, is a potato pest that can cope with variations in temperatures. Such adaptation requires molecular changes involving regulation of gene expression. Small non-coding RNAs, such as microRNAs (miRNAs) and PIWI-interacting RNAs (piRNAs), can influence protein expression and are modulated in different models of temperature adaptation. We thus hypothesize that select players involved in non-coding RNA synthesis could play a role in temperature adaptation in L. decemlineata. To test this hypothesis, transcript levels of Ago1, Ago2, Ago3, Dcr2a, Dcr2b, Expo-5, Siwi-1 and Siwi-2, components of pathways associated with small non-coding RNA production or function, were quantified by qRT-PCR in insects exposed to cold (-5 °C) or warm (40 °C) temperatures. Changes in Ago2 transcript levels were notably observed in insects submitted to these temperature challenges. Subsequent RNAi-mediated reduction of Ago2 transcript levels in L. decemlineata injected with Ago2-targeting dsRNA, while reducing Ago2 expression in injected insects to levels that were 0.23-fold (P < 0.05) the ones observed in control insects, did not impact cold survival. Interestingly, a similar approach revealed changes in mortality of insects exposed to warm temperatures with survival of 70.0 % in control insects compared to 32.4 % in Ago2 dsRNA-injected insects (P = 0.01). These results further support a temperature-mediated variation in the expression status of small non-coding RNAs in L. decemlineata and provide preliminary evidence that select targets underlying synthesis of small non-coding RNAs could influence adaptation to temperature changes.