engleski

Cellular response of marine diatom Chaetoceros pseudocurvistus to warming and nitrogen availability

Phytoplankton conversion of acquired inorganic nutrients to organic molecules for cellular growth and division is dependent on the environmental conditions. Nitrogen (N) excess and especially N scarcity as well as warming, lead to different responses in cellular metabolism with the aim of species acclimation or adaptation. Here, we use a multimethod approach to study the physiology and biochemical response of the marine diatom Chaetoceros pseudocurvistus to temperature increase (15 to 30 °C) and diverse N concentrations (excess (N:P=50), favorable (N:P=16) and deficiency (N:P=2)). The investigated stressors have varying degrees of effect on the cell, with excess of N having the least effect. High temperature has a stronger effect than nitrogen deficiency on significant cell death, N assimilation, increased Chl a accumulation, cessation of setae formation, and cell lipid remodeling. The most significant change in cellular lipids at 30 °C was observed in thylakoid lipids. Increased proportions of thylakoid lipids digalactosyldiacylglycerols (DGDG) and sulfoquinovosyldiacylglycerols (SQDG) are explained by the role of SQDG in achieving thermotolerance and the role of DGDG in balancing electrostatic repulsion between negatively charged SQDG. The reduced share of monogalactosyldiacylglycerols (MGDG) is explained by its role in stabilizing the changed thylakoid membrane. Nitrogen deficiency has a greater influence than temperature increase on the retardation of C. pseudocurvistus growth and reproduction, significant setae elongation, decreased phosphorus assimilation, increased lipid accumulation, and decreased protein synthesis. The setae elongation observed here likely serves to increase the surface area for inorganic nitrogen uptake. A favorable N:P ratio (16) is important for cellular health as inferred from the highest protein-to-cell lipid ratio.

Biochemical response ; marine diatom ; global warming ; lipid remodeling ; nitrogen stress

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