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The suborder Notothenioidae is comprised of Antarctic fishes, several of which have lost their ability to rapidly upregulate heat shock proteins in response to thermal stress, instead adopting a pattern of expression resembling constitutive genes. Given the cold-denaturing effect that sub-zero waters have on proteins, evolution in the Southern Ocean has likely selected for increased expression of molecular chaperones. These selective pressures may have also enabled retention of gene duplicates, bolstering quantitative output of cytosolic heat shock proteins (HSPs). Given that newly duplicated genes are under more relaxed selection, it is plausible that gene duplication enabled altered regulation of such highly conserved genes. To test for evidence of gene duplication, copy number of various isoforms within major heat shock gene families were characterized via qPCR and compared between the Antarctic notothen, Trematomus bernacchii, which lost the inducible heat shock response, and the non-Antarctic notothen, Notothenia angustata, which maintains an inducible heat shock response. The results indicate duplication of isoforms within the hsp70 and hsp40 super families have occurred in the genome of T. bernacchii. The findings suggest gene duplications may have been critical in maintaining protein folding efficiency in the sub-zero waters and provided an evolutionary mechanism of alternative regulation of these conserved gene families.
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Complementary Roles for Differential Gene Expression and Differential Exon Use in the Heat Shock Response of an Intertidal Copepod
Synopsis Understanding the mechanisms by which organisms adapt to variation in temperature is key to explaining their distribution across environments and to predicting their persistence to changing climate. The cellular response to heat shock, heat shock response (HSR), is a highly conserved mechanism for coping with elevated temperatures which functions through the upregulation of molecular chaperones like heat shock proteins (HSPs). Recent studies have also shown cellular response to heat shock can be quantitative (changing the magnitude of expression) or qualitative (differential usage of exons originating from the same gene). However, few studies have explored the time course of these two mechanisms in response to heat shock. We conducted a time-course experiment to examine the gene expression and exon usage changes in response to heat shock at four post-stress timepoints (30 min, 1 h, 2 h, 24 h) in a splash pool copepod, Tigriopus californicus. We detected signatures of both gene expression and exon usage changes across all timepoints. The magnitude of this response was higher at timepoints closer to heat shock and decreased with time post-heat shock. We observed that heat shock predominantly induced changes in gene expression in genes coding for chitin, HSPs, cellular growth, and differentiation. In contrast, we found that genes coding for peptidases showed both altered expression levels and exon usage. Genes associated with cellular metabolism and cytoskeletal elements primarily showed changes in exon usage. These ontology-specific response mechanisms provide new insights into the temporal landscape of HSR in Tigriopus and highlight the need to integrate qualitative and quantitative changes in gene expression to fully understand organismal responses to heat shock.
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- Award ID(s):
- 1923589
- PAR ID:
- 10681764
- Publisher / Repository:
- Integrative and Comparative Biology
- Date Published:
- Journal Name:
- Integrative And Comparative Biology
- Volume:
- 65
- Issue:
- 4
- ISSN:
- 1540-7063
- Page Range / eLocation ID:
- 1076 to 1086
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1093/icb/icaf032
