Recent findings from the team at the Institute of Oceanology, Chinese Academy of Sciences, in collaboration with experts in the field, have uncovered the mechanism behind how marine diatoms perceive and transmit signals related to population density, utilizing precise gene editing techniques. Their research results have been published in the Journal of the International Society for Microbial Ecology.
Just as animals on land and in the ocean communicate through sound, movement, and scent, single-celled microalgae in the ocean have their own methods of perception and communication. Among them, diatoms, as one of the most crucial photosynthetic organisms on Earth, play a significant role. Despite their seemingly low profile, diatoms annually fix organic carbon equivalent to the total amount sequestered by all tropical rainforests on land, greatly impacting ecosystems, atmospheric carbon dioxide levels, and global climate. Under suitable conditions, rapid proliferation of diatoms can lead to blooms. "Smart" diatom cells can perceive fluctuations in population density and adjust their physiological activities accordingly, thereby influencing the process of bloom formation and development. Furthermore, understanding the mechanisms of density perception and transmission in cells is crucial for the technological advancement of microalgae industrialization, providing a theoretical basis for ultra-high-density cultivation of microalgae. However, the current understanding of how algal cells achieve density perception and signal transduction remains unclear.
The research team focused on the representative marine single-celled model diatom - Phaeodactylum tricornutum - and designed an orthogonal experiment under different cell densities and light conditions to elicit signals carrying density information. Through RNA-Seq and weighted gene co-expression network analysis, the team identified four gene clusters with density-dependent expression patterns. By combining gene editing, physiological and biochemical experiments, and bioinformatics analysis, the team further pinpointed a potential key gene, PtSLC24A. Building upon this, through molecular genetics, cellular physiology, computational structural biology, and large-scale in situ oceanographic data, the team validated the role of PtSLC24A in intracellular signal transmission related to population density in marine diatoms.
The Triceratium dubium under the microscope, provided by the Marine Research Institute.
The diagram illustrating the population density sensing and regulatory mechanism mediated by SLC24A. Image provided by the Ocean Research Institute.
"We propose a calcium ion-mediated intracellular signaling mechanism in marine diatoms for population density signals: when cells receive population density signals, the PtSLC24A protein bound to the cell membrane accelerates the outflow of intracellular calcium ions to maintain specific intracellular calcium ion levels, thus transmitting the density signal intracellularly, regulating physiological processes including apoptosis, ultimately affecting population fate. To put it simply, just as humans rely on their eyes to see things, single-celled diatoms without eyes perceive the presence of 'buddies' around them through a calcium ion-mediated signaling pathway," said Dr. Gu Wenhui, co-corresponding author of the paper and a PhD from the Ocean Research Institute.
Dr. Wang Guangce, corresponding author of the paper and a researcher at the Ocean Research Institute, said, "This discovery not only provides new insights into the dynamic changes in population and the fate determination mechanism of diatom blooms, but also offers new ideas for achieving high-density cultivation of microalgae in industrial production."
This research was supported by the National Natural Science Foundation of China, the Key Research and Development Program of Shandong Province, and the National Algal Industry Technology System.
Paper details: https://doi.org/10.1093/ismejo/wrae039
