Table_1_The differing responses of central carbon cycle metabolism in male and female Sargassum thunbergii to ultraviolet-B radiation.docx

The enhancement of ultraviolet-B radiation (UV-B) radiation reaching the Earth’s surface due to ozone layer depletion is an important topic. Macroalgal species growing in the intertidal zone are often directly exposed to UV-B radiation periodically as the tide changes. In order to better understand the response of macroalgae to UV-B stressed condition, we studied the dominant dioecious intertidal macroalgae Sargassum thunbergii. After consecutive UV-B radiation treatments, we used metabonomics models to analyze and compare the maximum photosynthetic electron transport rate (ETRmax), central carbon cycle metabolism (CCCM) gene expression level, CCCM enzymic activities [pyruvate dehydrogenase and citrate synthase (PDH and CS)], and carbon-based metabolite (including pyruvate, soluble sugar, total amino acid, and lipids) content in male and female S. thunbergii. The results showed that under low and high UV-B radiation, the ETRmax values and six targeted CCCM gene expression levels were significantly higher in males than in females. Under high UV-B radiation, only the CS activity was significantly higher in males than in females. There was no significant difference in PDH activity between males and females. The CCCM models constructed using the metabonomics analysis demonstrate that S. thunbergii males and females exhibit obvious gender differences in their responses to UV-B radiation, providing us with a new understanding of the macroalgal gender differences under UV-B radiation, as past investigations always underestimated their diecious characteristics.

臭氧层损耗导致到达地球表面的紫外-B（UV-B）辐射增强，是当前重要的研究课题。潮间带生长的大型藻类物种会随潮汐变化周期性直接暴露于UV-B辐射之下。为深入阐明大型藻类对UV-B胁迫的响应机制，本研究选取潮间带优势雌雄异体大型藻类鼠尾藻（Sargassum thunbergii）作为研究对象。经连续UV-B辐射处理后，本研究采用代谢组学（metabonomics）方法，分析并比较了雌雄鼠尾藻的最大光合电子传递速率（ETRmax）、中心碳循环代谢（CCCM）基因表达水平、CCCM相关酶活性[丙酮酸脱氢酶与柠檬酸合酶（PDH和CS）]以及碳基代谢物（包括丙酮酸、可溶性糖、总氨基酸与脂质）含量。结果显示，在低、高剂量UV-B辐射处理下，雄性鼠尾藻的ETRmax值与6个目标CCCM基因的表达水平均显著高于雌性个体；仅在高剂量UV-B辐射处理下，雄性鼠尾藻的CS活性显著高于雌性，而雌雄个体间的PDH活性无显著差异。本研究通过代谢组学分析构建的CCCM模型表明，雌雄鼠尾藻对UV-B辐射的响应存在显著性别差异，这为重新认识UV-B辐射下大型藻类的性别差异提供了新视角——以往相关研究往往低估了其雌雄异体特性的影响。