Work

Simulated heatwave reduces resilience to subsequent combined high‐temperature and high‐carbon‐dioxide stress in a diatom

Year: 2026

Type: article

Abstract: Marine heatwaves pose a significant threat to marine ecosystems, yet the underlying biological mechanisms remain largely elusive. Here, we integrated physiological, transcriptomic, and DNA methylation (5‐methylcytosine and N6‐methyladenine, 5mC and 6mA) analyses to investigate the response of the model diatom Phaeodactylum tricornutum to a simulated heatwave and subsequent combined high‐temperature and high‐CO 2 stress. Phaeodactylum tricornutum initially tolerated the simulated heatwave with only minor physiological impacts. However, completing the 16‐d simulated heatwave followed by an 11‐d recovery significantly compromised its resilience to the subsequent combined stress. This decline was associated with transcriptional signatures of photosynthetic impairment and DNA damage. Moreover, we found that the transcriptional patterns of transposable elements from simulated heatwave to final stress challenge were closely associated with their genomic features and 5mC methylation prior to the simulated heatwave. Throughout the experiment, CG‐context methylation within the 5mC landscape remained stable, whereas non‐CG context methylation increased progressively. These 5mC dynamics were decoupled from transposable elements transcriptional changes, suggesting that 5mC‐mediated regulation was not the primary driver of their expression. In contrast, 6mA acted as a highly labile, stress‐responsive mark. We observed a severe global loss of 6mA under the subsequent combined high‐temperature and high‐CO 2 conditions, which coincided with transposable elements associated genome rearrangement. Collectively, these results suggest that 6mA, rather than 5mC, acts as a dynamic regulator in safeguarding genomic integrity in P. tricornutum . Our findings reveal that a prior simulated heatwave diminishes resilience to subsequent severe stresses, offering critical insights into how climate change impacts marine primary producers.

Source: Limnology and Oceanography

DOI: 10.1002/lno.70495