Sex-specific physiological-biochemical and multi-omics responses of Sargassum thunbergii to ocean acidification

Ocean acidification (OA), driven by increasing atmospheric CO2 concentrations, poses significant threats to the ecologically important intertidal macroalgae. Multiple previous studies have indicated species-specific responses to OA, the sex-specific physiological-biochemical responses and underlying molecular mechanisms in dioecious macroalgae remain poorly understood. In this study, we investigated the responses of male and female Sargassum thunbergii to OA (2000 ppm CO2) by integrating physiological-biochemical, transcriptomic, and metabolomic analyses. Both sexes maintained photosynthetic performance, with increased maximum relative electron transport rates (rETRmax). Males exhibited a growth-oriented strategy, characterized by higher accumulation of storage compounds like triglycerides and up-regulation of genes related to the photosynthesis and biosynthesis pathways. In contrast, females displayed a survival-oriented strategy, with reduced carbon storage, increased soluble protein and phenolic substance contents, and up-regulation of genes related to defense- and stress-response pathways. These findings provided physiological-biochemical and molecular evidence for a growth and defense trade-off between male and female S. thunbergii under OA. Our study provided the mechanistic insights into the sex-specific responses of marine macroalgae to global climate change and highlighted the importance of accounting for sexual dimorphism in predicting the ecological resilience of intertidal macroalgae populations under future ocean conditions.

由大气二氧化碳浓度升高驱动的海洋酸化（Ocean acidification, OA），对具有重要生态价值的潮间带大型藻类构成显著威胁。既往多项研究已揭示大型藻类对OA的物种特异性响应，但针对雌雄异体大型藻类的性别特异性生理生化响应及其潜在分子机制，目前仍知之甚少。本研究以鼠尾藻（Sargassum thunbergii）为研究对象，通过整合生理生化、转录组学与代谢组学分析，探究了其在2000 ppm CO2浓度的OA胁迫下的雌雄个体响应差异。结果显示，雌雄个体均维持了光合性能，且最大相对电子传递速率（maximum relative electron transport rates, rETRmax）有所提升。雄性个体呈现以生长为导向的策略，其甘油三酯等储存化合物的积累量更高，且与光合作用及生物合成通路相关的基因表达上调；与之相反，雌性个体则采取以生存为导向的策略，碳储存量降低，可溶性蛋白与酚类物质含量升高，同时与防御及应激反应通路相关的基因表达上调。本研究结果为OA胁迫下鼠尾藻雌雄个体间存在生长与防御权衡提供了生理生化与分子层面的证据，揭示了海洋大型藻类对全球气候变化的性别特异性响应机制，并强调了在预测未来海洋环境下潮间带大型藻类种群的生态恢复力时，纳入性二态性因素的重要性。