Abstract
Global warming is expected to reduce the nutrient concentration in the upper ocean and affect the physiology of marine diatoms, but the underlying molecular mechanisms controlling these physiological changes are currently unknown. To understand these mechanisms, here we investigated iTRAQ based proteomic profiling of diatom Skeletonema dohrnii in a multifactorial experimental with a combining change of temperature and silicate concentrations. In total, 3369 differently abundant proteins were detected in four different environmental conditions, and the function of all proteins was identified using Gene Ontology and KEGG pathway analysis. For discriminating the proteome variation among samples, multivariate statistical analysis (PCA, PLS-DA) was performed by comparing the protein ratio differences. Further, performing pathway analysis on diatom proteomes, we here demonstrated downregulation of photosynthesis, carbon metabolism, and ribosome biogenesis in the cellular process that leads to decrease the oxidoreductase activity and affects the cell cycle of the diatom. Using PLS-DA VIP score plot analysis, we identified 15 protein biomarkers for discriminating studied samples. Of these, five proteins or gene (rbcL, PRK, atpB, DNA-binding, and signal transduction) identified as key biomarkers, induced by temperature and silicate stress in diatom metabolism. Our results show that proteomic finger-printing of S. dohrnii with different environmental conditions adds biological information that strengthens marine phytoplankton proteome analysis.
Highlights
The increasing amount of anthropogenic greenhouse gas emission has resulted significant changes in the physical and chemical properties of the global ocean that have intense implications to the marine ecosystem (Pörtner et al, 2014)
We demonstrated the response of these genes on photosynthesis in different stress condition and these results were confirmed in diatom S. dohrnii
We observed downregulation of the photosynthesis process, carbon assimilation and utilization mechanisms and biological processes related to cell cycle regulation during elevated temperature and Si limitation in the diatom
Summary
The increasing amount of anthropogenic greenhouse gas emission has resulted significant changes in the physical and chemical properties of the global ocean that have intense implications to the marine ecosystem (Pörtner et al, 2014). It is assumed that the warming ocean will enhance the nutrient stratification and modulates the ecophysiology of marine organisms. A recent report described increasing sea surface temperature (SST), and depletion of nutrients affects the phytoplankton community resulting in 6% global biomass decrease by the end of this century (Chust et al, 2014). The unicellular microalgae (i.e., diatoms) are the dominant phytoplankton group covering 20% of global net primary productivity and fixing 30%–50% of the inorganic carbon in the ocean; it’s equivalent to all rainforest accounts (Field et al, 1998). Diatoms are the largest group of silicifying organisms (Otzen, 2012; Shrestha et al, 2012), and, changes in silicate concentration in the environment regulate their cell physiology and metabolism (Thangaraj et al, 2019). Temperature plays a vital role in their photosynthetic mechanisms (PSII, PSI, and LHCs), and transition in temperature could alter their photosynthetic mechanisms and regulate their carbon fixation process (Dong et al, 2016)
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