Chen Haihong, Shi Ziyan, Ji Hongxin, Ye Shengqi, Zhou Xiaoqian, Dan Zhijie, Shen Xin
Jiangsu Key Laboratory of Marine Bioresources and Environment, Jiangsu Key Laboratory of Marine Biotechnology, Jiangsu Ocean University, Lianyungang, 222005, China.
BMC Plant Biol. 2025 Feb 7;25(1):159. doi: 10.1186/s12870-025-06148-y.
The translocation of photoassimilates is a critical process that links the source and sink in plants, playing an irreplaceable role in maintaining source-sink balance, ensuring plant growth and development, and the formation of yield. Nevertheless, the mechanisms underlying the translocation of photosynthetic products in macroalgae are yet to be fully understood. The purpose of this study is to reveal the role of endocytosis in the translocation of photosynthetic products in the marine red alga Gracilariopsis lemaneiformis by investigating the uptake of photosynthetic products by endocytosis and the impact of endocytic activity on cellular ultrastructure, photosynthesis, and growth.
This study discovered that the endocytic activity in non-epidermal cells (NEC, sink cells) of G. lemaneiformis is significantly higher than that in epidermal cells (EC, source cells). NEC is capable of internalizing a greater amount of extracellular carbohydrates, such as sucrose, via endocytosis compared to EC. Further inhibition of endocytic activity in G. lemaneiformis using EIPA resulted in a significant reduction in the content of floridean starch within NEC, whereas the decrease in floridean starch content in EC was not statistically significant. Inhibition of endocytic activity led to an initial decline in photosynthetic efficiency of algal thalli within a few hours, which was followed by an increase as inhibition duration extended, yet the growth rate of the thalli remained substantially suppressed.
These findings indicate that endocytosis in G. lemaneiformis plays a role in regulating the cellular uptake of extracellular photoassimilates, which in turn influences the storage substances in sink cells and the overall growth and development of the algae. This study sheds new light on the regulatory mechanisms governing photoassimilate translocation in macroalgae.
光合产物的转运是连接植物源和库的关键过程，在维持源库平衡、确保植物生长发育以及产量形成方面发挥着不可替代的作用。然而，大型海藻中光合产物转运的潜在机制尚未完全明晰。本研究旨在通过研究光合产物的内吞摄取以及内吞活性对细胞超微结构、光合作用和生长的影响，揭示内吞作用在海洋红藻龙须菜光合产物转运中的作用。
本研究发现，龙须菜非表皮细胞（NEC，库细胞）中的内吞活性显著高于表皮细胞（EC，源细胞）。与EC相比，NEC能够通过内吞作用内化更多的细胞外碳水化合物，如蔗糖。使用EIPA进一步抑制龙须菜的内吞活性，导致NEC中红藻淀粉含量显著降低，而EC中红藻淀粉含量的下降无统计学意义。抑制内吞活性导致藻体光合效率在数小时内最初下降，随后随着抑制时间延长而上升，但藻体的生长速率仍受到显著抑制。
这些发现表明，龙须菜中的内吞作用在调节细胞对细胞外光合产物的摄取中发挥作用，进而影响库细胞中的储存物质以及藻类的整体生长发育。本研究为大型海藻中光合产物转运的调控机制提供了新的见解。
