Search

Cuvelier, Marie L. ... et al.-- 6 pages, 4 figures, 1 table, this article contains supporting information online at https://www.pnas.org/content/pnas/suppl/2010/07/27/1001665107.DCSupplemental/pnas.201001665SI.pdf.-- Data deposition: The sequences reported in this paper have been deposited in the Gen-Bank database (accession nos. HM581528–HM581638 and HM565909–HM565914). Other scaffolds with predicted genes from this Whole Genome Shotgun/454 project have been deposited at DNA Data Bank of Japan/European Molecular Biology Laboratory/GenBank under the accession no. AEAR00000000. The version described in this paper is the first version, AEAR01000000, Among eukaryotes, four major phytoplankton lineages are responsible for marine photosynthesis; prymnesiophytes, alveolates, stramenopiles, and prasinophytes. Contributions by individual taxa, however, are not well known, and genomes have been analyzed fromonly the latter two lineages. Tiny >picoplanktonic> members of the prymnesiophyte lineage have long been inferred to be ecologically important but remain poorly characterized. Here, we examine pico-prymnesiophyte evolutionary history and ecology using cultivation-independent methods. 18S rRNA gene analysis showed picoprymnesiophytes belonged to broadly distributed uncultivated taxa. Therefore, we used targeted metagenomics to analyze uncultured pico-prymnesiophytes sorted by flow cytometry from subtropical North Atlantic waters. The data reveal a composite nuclear-encoded gene repertoire with strong green-lineage affiliations, which contrasts with the evolutionary history indicated by the plastid genome. Measured pico-prymnesiophyte growth rates were rapid in this region, resulting in primary production contributions similar to the cyanobacterium Prochlorococcus. On average, pico-prymnesiophytes formed 25% of global picophytoplankton biomass, with differing contributions in five biogeographical provinces spanning tropical to subpolar systems. Elements likely contributing to success include high gene density and genes potentially involved in defense and nutrient uptake. Our findings have implications reaching beyond pico-prymnesiophytes, to the prasinophytes and stramenopiles. For example, prevalence of putative Ni-containing superoxide dismutases (SODs), instead of Fe-containing SODs, seems to be a common adaptation among eukaryotic phytoplankton for reducing Fe quotas in low-Fe modern oceans. Moreover, highly mosaic gene repertoires, although compositionally distinct for each major eukaryotic lineage, now seem to be an underlying facet of successful marine phytoplankton, Sequencing was under DE-AC02- 05CH11231, by a Department of Energy Community Sequencing Program award to A.Z.W. and J. Eisen. Support was in part by DE-FC02-02ER63453, NSF OCE-0722374, and NSF-MCB-0732448 (to A.E.A.); a National Human Genomic Research Institute, National Institutes of Health grant (to R.S.L.); National Oceanic and Atmospheric Administration and David and Lucile Packard Foundation (DLPF) grants (F.P.C.); NSF-OCE-0241740 (to B.J.B.); and major funding by NSF-OCE-0836721, the DLPF, and a Moore Foundation Young Investigator Award as well as Moore 1668 (to A.Z.W.). Author contribution details are given in SI Materials and Methods, Section 12

A semi-empirical, physical models have been derived of the quantum yield of the deactivation processes (fluorescence, photosynthesis and heat production) of excited states in phytoplankton pigment molecules. Besides some already known models (photosynthesis and fluorescence), this novel approach incorporates the dependence of the dissipation yield of the excitation energy in phytoplankton pigment molecules on heat. The quantitative dependences of the quantum yields of these three processes on three fundamental parameters of the marine environment are defined: the chlorophyll concentration in the surface water layer Ca(0) (the basin trophicity), the irradiance PAR(z) and the temperature temp(z) at the study site. The model is complemented with two other relevant models describing the quantum yield of photosynthesis and of natural Sun-Induced Chlorophyll a Fluorescence (SICF) in the sea, derived earlier by the author or with her participation on the basis of statistical analyses of a vast amount of empirical material. The model described in the present paper enables the estimation of the quantum yields of phytoplankton pigment heat production for any region and season, in waters of any trophicity at different depths from the surface to depths of ca 60 m. The model can therefore be used to estimate the yields of these deactivation processes in more than half the thickness of the euphotic zone in oligotrophic waters and in the whole thickness (and deeper) of this zone in mesotrophic and eutrophic waters. In particular these relationships may be useful for a component analysis of the budget of light energy absorbed by phytoplankton pigments, namely, its utilization in fluorescence, photochemical quenching and nonphotochemical radiationless dissipation – i.e. direct heat production.