Nudix Hydrolase as a Target for Regulating High Temperature Tolerance in Marine Diatoms

Diatoms, as a vital component of marine ecosystems, face severe threats to their productivity and species composition due to increasing ocean temperatures. Although the effects of high temperatures on diatom growth and physiology have been thoroughly studied, the regulatory mechanisms in response to high temperature are still poorly understood. In this study, we identified Nudix hydrolases (Nudix) from the marine model diatom Phaeodactylum tricornutum as a key regulator of high temperature tolerance. We discovered that Nudix is a temperature-sensitive gene and its expression is induced by high-temperature. Under high-temperature stress, overexpression of Nudix markedly reduces reactive oxygen species (ROS) production and enhances ROS scavenging capacity, thereby decreasing lipid peroxidation and cell death rate to improve the high-temperature tolerance of P. tricornutum. Conversely, the silencing of Nudix induces excessive ROS production in P. tricornutum and reduces its high-temperature tolerance. Subcellular localization combined with the photosynthetic activity analyses further demonstrated that Nudix, localized in the chloroplast, prevents energetic electron accumulation and excessive reduction in the photosynthetic electron transport chain by increasing the electron transport rate, thereby suppressing ROS production at high-temperature stress. Collectively, our findings highlight the importance of Nudix in high-temperature tolerance of diatoms and provide insights into how marine diatoms acclimate to high temperature.