Abstract
In natural fish populations, temperature increases can result in shifts in important phenotypic traits. DNA methylation is an epigenetic mechanism mediating phenotypic changes. However, whether temperature increases of the magnitude predicted by the latest global warming models can affect DNA methylation is unknown. Here, we exposed European sea bass to moderate temperature increases in different periods within the first two months of age. We show that increases of even 2 °C in larvae significantly changed global DNA methylation and the expression of ecologically-relevant genes related to DNA methylation, stress response, muscle and organ formation, while 4 °C had no effect on juveniles. Furthermore, DNA methylation changes were more marked in larvae previously acclimated to a different temperature. The expression of most genes was also affected by temperature in the larvae but not in juveniles. In conclusion, this work constitutes the first study of DNA methylation in fish showing that temperature increases of the magnitude predicted by the latest global warming models result in stage-dependent alterations in global DNA methylation and gene expression levels. This study, therefore, provides insights on the possible consequences of climate change in fish mediated by genome-wide epigenetic modifications.
Highlights
In natural fish populations, elevated temperatures associated with global warming[1] can result in shifts in a variety of phenotypic traits, mostly related to reproduction and life history[2]
Differentiation of DNA methylation between groups was visualized by a Principal Coordinates Analysis (PCoA)[46]
In experiment 1.1, determination of differentiation of DNA methylation between groups by Analysis of Molecular Variance (AMOVA) based on the distance matrix calculated from binary polymorphic MSL showed significant differences (p < 0.001) in global DNA methylation between larvae that had been kept at a constant temperature of 15, 17 or 19 °C since day 0, with a ΦST of 0.1626 among groups (Table 1; see Table S3 for pairwise comparisons)
Summary
In natural fish populations, elevated temperatures associated with global warming[1] can result in shifts in a variety of phenotypic traits, mostly related to reproduction and life history[2]. Previous studies have shown that sea bass is sensitive to temperature changes, in particular during early development, from 0 to around 60 days fertilization (dpf), which is considered its thermosensitive period (TSP), affecting a variety of morphological and physiological aspects[31,32,33,34] One of these aspects is population sex ratio, which was shown to be mediated, at least in part, by DNA methylation changes in a key gene involved in sex differentiation[35]. The goal of this study was to determine whether small temperature variations experienced during different periods of fish early life, and within the range established by the latest global warming models, can affect global DNA methylation and the expression of a suite of ecologically important genes relevant for survival and development. We show that the first 15 days of life are critical since changes in temperature that include this period can elicit changes in both DNA methylation and gene expression
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