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Abstract:
Phagocytosis is a fundamental process in marine ecosystems by which prey organisms are consumed and their biomass
incorporated in food webs or remineralized. However, studies searching for the genes underlying this key ecological process
in free-living phagocytizing protists are still scarce, in part due to the lack of appropriate ecological models. Our reanalysis
of recent molecular datasets revealed that the cultured heterotrophic flagellate Cafeteria burkhardae is widespread in the
global oceans, which prompted us to design a transcriptomics study with this species, grown with the cultured
flavobacterium Dokdonia sp. We compared the gene expression between exponential and stationary phases, which were
complemented with three starvation by dilution phases that appeared as intermediate states. We found distinct expression
profiles in each condition and identified 2056 differentially expressed genes between exponential and stationary samples.
Upregulated genes at the exponential phase were related to DNA duplication, transcription and translational machinery,
protein remodeling, respiration and phagocytosis, whereas upregulated genes in the stationary phase were involved in signal
transduction, cell adhesion, and lipid metabolism. We identified a few highly expressed phagocytosis genes, like peptidases and proton pumps, which could be used to target this ecologically relevant process in marine ecosystems.
