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A phosphate starvation response gene (psr1-like) is present and expressed in Micromonas pusilla and other marine algae

Cara L. Fiore*, Harriet Alexander, Melissa C. Kido Soule, Elizabeth B. Kujawinski

*Corresponding author:

ABSTRACT: Phosphorus (P) limits primary production in regions of the surface ocean, and many plankton species exhibit specific physiological responses to P-deficiency. The metabolic response of Micromonas pusilla, an ecologically relevant marine photoautotroph, to P-deficiency was investigated using metabolomics and comparative genomics. The concentrations of some intracellular metabolites were elevated in the P-deficient cells (e.g., xanthine, inosine), and genes involved in the associated metabolic pathways shared a predicted conserved amino acid motif in the non-coding regions of each gene. The presence of the conserved motif suggests that these genes may be co-regulated, and the motif may constitute a regulatory element for binding a transcription factor, specifically that of Psr1 (Phosphate starvation response). A putative phosphate starvation response gene (psr1-like) was identified in M. pusilla with homology to well characterized psr1/phr1 genes in algae and plants, respectively. This gene appears to be present and expressed in other marine algal taxa (e.g., Emiliania huxleyi) in field sites that are chronically phosphorus-limited. Results from the present study have implications for understanding phytoplankton taxon-specific roles in mediating P cycling in the ocean.