Characterization and expression of heat shock and immune genes in natural populations of Prodiamesa olivacea (Diptera) exposed to thermal stress.

This paper characterizes the heat stress response (HSR) and explores the impact of temperatures on the immune response of larvae from two chironomid species, Prodiamesa olivacea and Chironomus riparius. Genes involved in crucial metabolic pathways were de novo identified in P. olivacea: Hsp27, Hsp60, Hsp70, Hsc70, Cdc37, and HSF for the heat stress response (HSR) and TOLL, PGRP, C-type lectin, and JAK/hopscotch for the immune system response (ISR). Quantitative real-time PCR was used to evaluate the expression levels of the selected genes in short-term treatments (up to 120') at high temperatures (35 °C and 39 °C). Exposing P. olivacea to elevated temperatures resulted in HSR induction with increased expression of specific heat shock genes, suggesting the potential of HSPs as early indicators of acute thermal stress. Surprisingly, we found that heat shock represses multiple immune genes, revealing the antagonist relation between the heat shock response and the innate immune response in P. olivacea. Our results also showed species-dependent gene responses, with more significant effects in P. olivacea, for most of the biomarkers studied, demonstrating a higher sensitivity in this species to environmental stress conditions than that of C. riparius. This work shows a multi-species approach that enables a deeper understanding of the effects of heat stress at the molecular level in aquatic dipterans.