Plastic products contribute heavily to anthropogenic pollution of the oceans. Small plastic particles in the microscale and nanoscale ranges have been found in all marine ecosystems, but little is known about their effects upon marine organisms. In this study, we examine changes in cell growth, aggregation, and gene expression of two symbiotic dinoflagellates of the family Symbiodiniaceae, Symbiodinium tridacnidorum (clade A3), and Cladocopium sp. (clade C) under exposure to 42-nm polystyrene beads. In laboratory experiments, the cell number and aggregation were reduced after 10 days of nanoplastic exposure at 0.01, 0.1, and 10 mg/L concentrations, but no clear correlation with plastic concentration was observed. Genes involved in dynein motor function were upregulated when compared to control conditions, while genes related to photosynthesis, mitosis, and intracellular degradation were downregulated. Overall, nanoplastic exposure led to more genes being downregulated than upregulated and the number of genes with altered expression was larger in Cladocopium sp. than in S. tridacnidorum, suggesting different sensitivity to nano-plastics between species. Our data show that nano-plastic inhibits growth and alters aggregation properties of microalgae, which may negatively affect the uptake of these indispensable symbionts by coral reef organisms.
Dinoflagellates are some of the most common eukaryotic cells in the ocean, but have very unusual nuclei. Many exhibit a form of closed mitosis (dinomitosis) wherein the nuclear envelope (NE) invaginates to form one or more trans-nuclear tunnels. Rather than contact spindles directly, the chromatids then bind to membrane-based kinetochores on the NE. To better understand these unique mitotic features, we reconstructed the nuclear architecture of Polykrikos kofoidii in 3D using focused ion beam scanning electron microscopy (FIB-SEM) in conjunction with high-pressure freezing, freeze-substitution, TEM, and confocal microscopy. We found that P. kofoidii possessed six nuclear tunnels, which were continuous with a reticulating network of membranes that has thus far gone unnoticed. These membranous extensions interconnect the six tunnels while ramifying throughout the nucleus to form a “nuclear net.” To our knowledge, the nuclear net is the most elaborate endomembrane structure described within a nucleus. Our findings demonstrate the utility of tomographic approaches for detecting 3D membrane networks and show that nuclear complexity has been underestimated in Polykrikos kofoidii and, potentially, in other dinoflagellates.
Plastic products contribute heavily to anthropogenic pollution of the oceans. Small plastic particles in the micro- and nanoscale ranges have been found in all marine ecosystems, but little is known about their effects upon marine organisms. In this study we examine changes in cell growth, aggregation, and gene expression of two symbiotic dinoflagellates of the family Symbiodiniaceae, Symbiodinium tridacnidorum (clade A3) and Cladocopium sp. (clade C), under exposure to 42-nm polystyrene beads. In laboratory experiments, cell number and aggregation were reduced after 10 days of nanoplastic exposure at 0.01, 0.1, and 10 mg/L concentrations, but no clear correlation with plastic concentration was observed. Genes involved in dynein motor function were upregulated compared to control conditions, while genes related to photosynthesis, mitosis, and intracellular degradation were downregulated. Overall, nanoplastic exposure led to more genes being downregulated than upregulated and the number of genes with altered expression was larger in Cladocopium sp. than in S. tridacnidorum, suggesting different sensitivity to nanoplastic between species. Our data show that nanoplastic inhibits growth and alters aggregation properties of microalgae, which may negatively affect the uptake of these indispensable symbionts by coral reef organisms.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.