CriTER-A: A Novel Temperature-Dependent Noncoding RNA Switch in the Telomeric Transcriptome of Chironomus riparius.

The telomeric transcriptome of Chironomus riparius has been involved in thermal stress response. One of the telomeric transcripts, the so-called CriTER-A variant, is highly overexpressed upon heat shock. On the other hand, its homologous variant CriTER-B, which is the most frequently encoded noncoding RNA in the telomeres of C. riparius, is only slightly affected by thermal stress. Interestingly, both transcripts show high sequence homology, but less is known about their folding and how this could influence their differential behaviour. Our study suggests that CriTER-A folds as two different conformers, whose relative proportion is influenced by temperature conditions. Meanwhile, the CriTER-B variant shows only one dominant conformer. Thus, a temperature-dependent conformational equilibrium can be established for CriTER-A, suggesting a putative functional role of the telomeric transcriptome in relation to thermal stress that could rely on the structure-function relationship of the CriTER-A transcripts.

Characterization of six small HSP genes from Chironomus riparius (Diptera, Chironomidae): Differential expression under conditions of normal growth and heat-induced stress.

Small heat shock proteins (sHSPs) comprise the most numerous, structurally diverse, and functionally uncharacterized family of heat shock proteins. Several Hsp genes (Hsp 90, 70, 40, and 27) from the insect Chironomus riparius are widely used in aquatic toxicology as biomarkers for environmental toxins. Here, we conducted a comparative study and characterized secondary structure of the six newly identified sHsp genes Hsp17, Hsp21, Hsp22, Hsp23, Hsp24, and Hsp34. A characteristic α-crystallin domain is predicted in all the new proteins. Phylogenetic analysis suggests a strong relation to other sHSPs from insects and interesting evidence regarding evolutionary origin and duplication events. Comparative analysis of transcription profiles for Hsp27, Hsp70, and the six newly identified genes revealed that Hsp17, Hsp21, and Hsp22 are constitutively expressed under normal conditions, while under two different heat shock conditions these genes are either not activated or are even repressed (Hsp22). In contrast, Hsp23, Hsp24, and Hsp34 are significantly activated along with Hsp27 and Hsp70 during heat stress. These results strongly suggest functional differentiation within the small HSP subfamily and provide new data to help understand the coping mechanisms induced by stressful environmental stimuli.

Surviving in a multistressor world: Gene expression changes in earthworms exposed to heat, desiccation, and chemicals.

An investigation of the effects of anthropogenic stress on terrestrial ecosystems is urgently needed. In this work, we explored how exposure to heat, desiccation, and chemical stress alters the expression of genes that encode heat shock proteins (HSPs), an enzyme that responds to oxidative stress (CAT), hypoxia-related proteins (HIF1 and HYOU), and a DNA repair-related protein (PARP1) in the earthworm Eisenia fetida. Exposure to heat (31°C) for 24 h upregulated HSPs and hypoxia-related genes, suggesting possible acquired thermotolerance. Desiccation showed a similar expression profile; however, the HSP response was activated to a lesser extent. Heat and desiccation activated the small HSP at 24 h, suggesting that they may play a role in adaptation. Simultaneous exposure to endosulfan and temperature for 7 h upregulated all of the evaluated genes, implicating a coordinated response involving multiple biological processes to ensure survival and acclimation. These results highlight the relevance of multistress analysis in terrestrial invertebrates.

Understanding Diversity, Evolution, and Structure of Small Heat Shock Proteins in Annelida Through in Silico Analyses.

Small heat shock proteins (sHsps) are oligomeric stress proteins characterized by an α-crystallin domain (ACD). These proteins are localized in different subcellular compartments and play critical roles in the stress physiology of tissues, organs, and whole multicellular eukaryotes. They are ubiquitous proteins found in all living organisms, from bacteria to mammals, but they have never been studied in annelids. Here, a data set of 23 species spanning the annelid tree of life, including mostly transcriptomes but also two genomes, was interrogated and 228 novel putative sHsps were identified and manually curated. The analysis revealed very high protein diversity and showed that a significant number of sHsps have a particular dimeric architecture consisting of two tandemly repeated ACDs. The phylogenetic analysis distinguished three main clusters, two of them containing both monomeric sHsps, and ACDs located downstream in the dimeric sHsps, and the other one comprising the upstream ACDs from those dimeric forms. Our results support an evolutionary history of these proteins based on duplication events prior to the Spiralia split. Monomeric sHsps 76) were further divided into five subclusters. Physicochemical properties, subcellular location predictions, and sequence conservation analyses provided insights into the differentiating elements of these putative functional groups. Strikingly, three of those subclusters included sHsps with features typical of metazoans, while the other two presented characteristics resembling non-metazoan proteins. This study provides a solid background for further research on the diversity, evolution, and function in the family of the sHsps. The characterized annelid sHsps are disclosed as essential for improving our understanding of this important family of proteins and their pleotropic functions. The features and the great diversity of annelid sHsps position them as potential powerful molecular biomarkers of environmental stress for acting as prognostic tool in a diverse range of environments.

Effect of environmental stressors on the mRNA expression of ecdysone cascade genes in Chironomus riparius.

Chemical compounds produced by humans are continuously reaching the environment. In this work, we characterised the expression patterns of important endocrine-related genes involved in the ecdysone pathway in the fourth larval instar of the model species Chironomus riparius after exposure to three chemicals: ethinyl oestradiol (EE), nonylphenol (NP) and bis(tributyltin) oxide (TBTO). We used real-time PCR to analyse the gene expression levels of ecdysone receptor (EcR) and ultraspiracle (usp), two genes that encode the dimerising partners of the functional ecdysone receptor; the orphan receptor ERR (oestrogen-related receptor), with an unknown function in invertebrates; and E74, an early response gene induced by ecdysteroids. We estimated the bioaccumulation potential, bioavailability and physicochemical properties of these chemicals, together with a number of other exogenous agents known to interfere with the hormonal system. We also provide a review of previous transcriptional studies showing the effect of all these chemicals on ecdysone cascade genes. This analysis provides useful data for future ecotoxicological studies involving invertebrate species. CAPSULE: Changes in transcriptional activities of EcR, E74, usp and ERR genes after exposure to endocrine-disrupting chemicals would be useful as molecular bioindicators of endocrine disruption in Chironomus riparius.

BPA and its analogues (BPS and BPF) modify the expression of genes involved in the endocrine pathway and apoptosis and a multi drug resistance gene of the aquatic midge Chironomus riparius (Diptera).

Many countries are limiting the use of bisphenol A (BPA) because evidence shows it is dangerous to human health and wildlife. For the manufacturing of polycarbonate plastics, bisphenol S (BPS) and bisphenol F (BPF) are proposed as safer alternatives. They have already been released into the aquatic environment without previously available information about their potential adverse effects. In this study, we compared the effects of BPA, BPS and BPF exposure to the expression profile of genes involved in the endocrine pathway (EcR and E74), ecdysone metabolism (Cyp18a1 and Shadow), apoptosis (DRONC) and the multidrug resistance-associated protein 1 gene (MRP1) in the midge, Chironomus riparius (Diptera). The three toxicants increased Shadow expression, which is involved in ecdysone synthesis, but only BPF significantly altered Cyp18a1, which is implicated in ecdysone degradation. BPS and BPF modified EcR and E74 expression; BPF upregulated the effector caspase DRONC. Furthermore, BPA significantly increased MRP1 expression. This study provides insights into the action of bisphenols at the molecular level and highlights the potential risks of BPS and BPF as BPA alternatives.

ncRNAs and thermoregulation: a view in prokaryotes and eukaryotes.

During cellular stress response, a widespread inhibition of transcription and blockade of splicing and other post-transcriptional processing is detected, while certain specific genes are induced. In particular, free-living cells constantly monitor temperature. When the thermal condition changes, they activate a set of genes coding for proteins that participate in the response. Non-coding RNAs, ncRNAs, and conformational changes in specific regions of mRNAs seem also to be crucial regulators that enable the cell to adjust its physiology to environmental changes. They exert their effects following the same principles in all organisms and may affect all steps of gene expression. These ncRNAs and structural elements as related to thermal stress response in bacteria are reviewed. The resemblances to eukaryotic ncRNAs are highlighted.