# Transcriptome Analyses Reveal the Molecular Response of Juvenile Greater Amberjack (Seriola dumerili) to Marine Heatwaves

## TL;DR

This study explores how juvenile greater amberjack respond to marine heatwaves at the molecular level, revealing key genes and pathways involved in their stress response.

## Contribution

The study identifies specific gene expression changes in Seriola dumerili under marine heatwave conditions, providing new insights into their adaptive mechanisms.

## Key findings

- Heat shock proteins and genes related to oxidative stress, immune responses, and energy metabolism are upregulated during short-term MHW exposure.
- Repeated exposure to MHWs leads to downregulation of these genes, indicating a loss of adaptive capacity and metabolic dysfunction.
- The findings suggest that S. dumerili cannot sustain adaptive responses under prolonged or repeated MHW stress.

## Abstract

Marine heatwaves (MHWs) impact the sustainability of marine life and fisheries, including commercially important species such as Seriola dumerili. However, little is known about how this species responds to the stress of MHWs at the molecular level. In this study, we examined the gene expression changes and biological processes involved in the response of S. dumerili to short-lasting and repeatedly occurring MHWs. These findings provide a scientific foundation for understanding the adaptive mechanisms of S. dumerili to MHWs conditions.

Marine heatwaves (MHWs) have recently become more frequent, intense, and prolonged, posing significant threats to marine life and fisheries. In this study, transcriptomic analysis was employed to investigate the genes and pathways in Seriola dumerili that respond to MHW-induced stress at 28 °C (T28) and 32 °C (T32), using 24 °C (T24) as the control. Transcriptome sequencing revealed that 17 differentially expressed genes (DEGs) belonging to the heat shock protein (HSP) families—HSP30, HSP40, HSP70, and HSP90—were significantly upregulated under short-lasting MHW stress in the T24-4d vs. T32-4d comparison. Additionally, genes related to oxidative stress (e.g., protein disulfide isomerase family A member 6 [pdia6]), immune responses (e.g., interferon regulatory factor 5 [irf5]), and energy metabolism (e.g., hexokinase-1 [hk1]) were also identified. Enrichment analysis of DEGs in the T24-4d vs. T32-4d group revealed that S. dumerili exhibited adaptive responses to MHWs through the upregulation of HSPs and the activation of antioxidant, energy metabolism, and immune response pathways. However, in the T24-13d vs. T32-13d group, DEGs associated with these pathways were either not significantly expressed or were downregulated. These findings indicate that S. dumerili is unable to sustain its adaptive responses under repeated, intense MHW exposure, resulting in the disorder of its antioxidant defense system, immune suppression, and metabolic dysfunction. This study provides valuable insights into the molecular responses of S. dumerili to MHWs and supports the selection for thermal resistance in this species.