SLC24A-mediated calcium exchange as an indispensable component of the diatom cell density-driven signaling pathway

Diatom bloom is characterized by a rapid increase of population density. Perception of population density and physiological responses can significantly influence their survival strategies, subsequently impacting bloom fate. The population density itself can serve as a signal, which is perceived through chemical signals or chlorophyll fluorescence signals triggered by high cell density, and their intracellular signaling mechanisms remain to be elucidated. In this study, we focused on the model diatom, Phaeodactylum tricornutum, and designed an orthogonal experiment involving varying cell densities and light conditions, to stimulate the release of chemical signals and light-induced chlorophyll fluorescence signals. Utilizing RNA-Seq and Weighted Gene Co-expression Network Analysis, we identified four gene clusters displaying density-dependent expression patterns. Within these, a potential hub gene, PtSLC24A, encoding a Na+/Ca2+ exchanger, was identified. Based on molecular genetics, cellular physiology, computational structural biology, and in situ oceanic data, we propose a potential intracellular signaling mechanism related to cell density in marine diatoms using Ca2+: upon sensing population density signals mediated by chemical cues, the membrane-bound PtSLC24A facilitates the efflux of Ca2+ to maintain specific intracellular calcium levels, allowing the transduction of intracellular density signals, subsequently regulating physiological responses, including cell apoptosis, ultimately affecting algal blooms fate. These findings shed light on the calcium-mediated intracellular signaling mechanism of marine diatoms to changing population densities, and enhances our understanding of diatom bloom dynamics and their ecological implications.

Calcium extrusion regulatory molecules: differential expression during pregnancy in the porcine uterus

Calcium ions in the uterine endometrium are essential for the establishment and maintenance of pregnancy, but the cellular and molecular mechanisms of calcium ion regulation in the endometrium are not fully understood. Our previous study in pigs found that calcium regulatory molecules, transient receptor potential, vanilloid type 6 and calbindin-D9K, are expressed in the uterine endometrium during the estrous cycle and pregnancy. However, we did not determine the expression of calcium extrusion regulatory molecules, plasma membrane calcium ATPases (ATP2Bs), sodium/calcium exchangers (SLC8As), or potassium-dependent sodium/calcium exchangers (SLC24As), in the uterine endometrium and conceptuses. Thus, in this study we determine whether ATP2Bs, SCL8As, and SLC24As are expressed in the uterine endometrium during the estrous cycle and pregnancy and in conceptuses during early pregnancy. Real-time RT-PCR analysis showed that ATP2Bs, SLC8As, and SLC24As were expressed in the uterine endometrium in a pregnancy status- and stage-specific manner. Conceptuses during early pregnancy also expressed these molecules. In situ hybridization analysis showed that ATP2B1, SLC8A1, and SLC24A4 were localized mainly to luminal and glandular epithelium and stromal cells in the endometrium during pregnancy. These results indicate that calcium extrusion regulatory molecules are expressed in the uterine endometrium during the estrous cycle and pregnancy and in conceptuses during early pregnancy, indicating that calcium extrusion regulatory molecules may play important roles in the establishment and maintenance of pregnancy by regulating calcium ion concentration in the uterine endometrium in pigs.