Emiliania Huxleyi (Prymnesiophyceae): Nitrogen-metabolism genes and their expression in response to external nitrogen sources.

Bruhn, Annette, LaRoche, Julie and Richardson, Katherine (2010) Emiliania Huxleyi (Prymnesiophyceae): Nitrogen-metabolism genes and their expression in response to external nitrogen sources. Journal of Phycology, 46 (2). pp. 266-277. DOI 10.1111/j.1529-8817.2010.00809.x.

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Abstract

The availability and composition of dissolved nitrogen in ocean waters are factors that influence species composition in natural phytoplankton communities. The same factors affect the ratio of organic to inorganic carbon incorporation in calcifying species, such as the coccolithophore Emiliania huxleyi (Lohman) W. W. Hay et H. Mohler. E. huxleyi has been shown to thrive on various nitrogen sources, including dissolved organic nitrogen. Nevertheless, assimilation of dissolved nitrogen under nitrogen-replete and -limited conditions is not well understood in this ecologically important species. In this study, the complete amino acid sequences for three functional genes involved in nitrogen metabolism in E. huxleyi were identified: a putative formamidase, a glutamine synthetase (GSII family), and assimilatory nitrate reductase. Expression patterns of the three enzymes in cells grown on inorganic as well as organic nitrogen sources indicated reduced expression levels of nitrate reductase when cells were grown on NH(4)+ and a reduced expression level of the putative formamidase when growth was on NO(3)-. The data reported here suggest the presence of a nitrogen preference hierarchy in E. huxleyi. In addition, the gene encoding for a phosphate repressible phosphate permease was more highly expressed in cells growing on formamide than in cells growing on inorganic nitrogen sources. This finding suggests a coupling between phosphate and nitrogen metabolism, which might give this species a competitive advantage in nutrient-depleted environments. The potential of using expression of genes investigated here as indicators of specific nitrogen-metabolism strategies of E. huxleyi in natural populations of phytoplankton is discussed.

Document Type: Article
Keywords: Biological Oceanography; Emiliania huxleyi; formamidase; gene expression; glutamine synthetase; nitrate reductase; nitrogen; qPCR; GLUTAMINE-SYNTHETASE GENES; NITRATE REDUCTASE GENE; MOLECULAR PHYLOGENETIC ANALYSIS; DIATOM SKELETONEMA-COSTATUM; MARINE-PHYTOPLANKTON; CHLAMYDOMONAS-REINHARDTII; ASPERGILLUS-NIDULANS; CHLORELLA-VULGARIS; AMINO-ACIDS; TRANSCRIPTIONAL REGULATION
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BI Biological Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1111/j.1529-8817.2010.00809.x
ISSN: 0022-3646
Date Deposited: 10 Jan 2012 13:17
Last Modified: 25 Jun 2018 12:05
URI: http://oceanrep.geomar.de/id/eprint/13353

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