Key Laboratory of Marine Environment and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Laboratory for Marine Ecology and Environmental Science, Qingdao Marine Science and Technology Center, Qingdao 266237, China; Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao 266100, China.
Key Laboratory of Marine Environment and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China.
Gene. 2025 Jan 15;933:148915. doi: 10.1016/j.gene.2024.148915. Epub 2024 Sep 6.
Diatoms play a crucial role in marine primary productivity through carbon fixation, which is essential for understanding the operation of marine biological pumps and carbon sinks. This study focuses on the phosphoenolpyruvate carboxylase (PEPC) gene, a key enzyme in the carbon assimilation pathway of diatoms, by investigating the consequences of its silencing in Skeletonema costatum. Through this approach, we aimed to clarify the distinct contributions of PEPC to the overall carbon fixation process. The mutant strains of S. costatum were subjected to thorough analysis to identify any shifts in physiological behavior, alterations in the gene expression of key carbon-fixing enzymes, and changes in the associated enzyme activities. Notably, the inhibition of the PEPC gene did not significantly affect the growth rate of S. costatum; however, it did have a notable impact on the photosynthetic apparatus, as evidenced by a reduction in the maximal electron transport rate and a decline in light utilization efficiency. A significant decrease was observed in both the enzymatic activity and gene expression of PEPCase. This down-regulation also affected other enzymes integral to the carbon fixation pathway, such as phosphoenolpyruvate carboxykinase and pyruvate-phosphate dikinase, indicating a wider metabolic perturbation. In contrast, the expression and activity of the Rubisco enzyme suggested that some facets of carbon fixation remained resilient. Furthermore, the substantial upregulation of carbonic anhydrase expression and activity probably represented an adaptive mechanism to sustain the inorganic carbon supply necessary for the carboxylation process of Rubisco. This research not only underscores the pivotal role of the PEPC gene in the carbon fixation of S. costatum but also expands our comprehension of carbon fixation mechanisms in diatoms.
硅藻通过碳固定在海洋初级生产力中发挥着关键作用，这对于理解海洋生物泵和碳汇的运作至关重要。本研究专注于磷酸烯醇丙酮酸羧化酶（PEPC）基因，该基因是硅藻碳同化途径中的关键酶，通过研究其在中肋骨条藻中的沉默所带来的影响，旨在阐明 PEPC 对整体碳固定过程的独特贡献。对中肋骨条藻的突变株进行了全面分析，以确定其在生理行为、关键碳固定酶的基因表达以及相关酶活性方面的任何变化。值得注意的是，PEPC 基因的抑制并未显著影响中肋骨条藻的生长速率；然而，它确实对光合作用器产生了显著影响，表现为最大电子传递速率的降低和光利用效率的下降。PEPCase 的酶活性和基因表达均显著下降。这种下调还影响了碳固定途径中的其他关键酶，如磷酸烯醇丙酮酸羧激酶和丙酮酸-磷酸二激酶，表明代谢受到更广泛的干扰。相比之下，Rubisco 酶的表达和活性表明，碳固定的某些方面仍然具有弹性。此外，碳酸酐酶表达和活性的大量上调可能代表了一种适应机制，以维持 Rubisco 羧化过程所需的无机碳供应。这项研究不仅强调了 PEPC 基因在中肋骨条藻碳固定中的关键作用，还扩展了我们对硅藻碳固定机制的理解。
