Algal Biogeography: Metagenomics Shows Distribution of a Picoplanktonic Pelagophyte
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Current Biology Vol 22 No 17 R682 14. Whitehead, M.R., and Peakall, R. (2009). evolution of deceptive pollination in orchids. 20. Mitchell, R.J. (2004). Heritability of nectar traits: Integrating floral scent, pollination ecology Biol. Rev. 81, 219–235. why do we know so little? Ecology 85, and population genetics. Funct. Ecol. 23, 17. Schiestl, F.P. (2005). On the success of 1527–1533. 863–874. a swindle: pollination by deception in orchids. 15. Klahre, U., Gurba, A., Hermann, K., Naturwissenschaften 92, 255–264. Saxenhofer, M., Bossolini, E., Guerin, Patrick 18. Cozzolino, S., and Widmer, A. (2005). Orchid Evolution, Ecology and Genetics, Research M., and Kuhlemeier, C. (2011). Pollinator choice diversity: an evolutionary consequence of School of Biology, The Australian National in Petunia depends on two major genetic loci deception? Trends Ecol. Evol. 20, 487–494. University, Canberra, ACT 0200, Australia. for floral scent production. Curr. Biol. 21, 19. Karron, J.D., Ivey, C.T., Mitchell, R.J., E-mail: [email protected] 730–739. Whitehead, M.R., Peakall, R., and Case, A.L. 16. Jersa´ kova´ , J., Johnson, S.D., and (2012). New perspectives on the evolution of Kindlmann, P. (2006). Mechanisms and plant mating systems. Ann. Bot. 109, 493–503. http://dx.doi.org/10.1016/j.cub.2012.06.072 Algal Biogeography: Metagenomics the total phytoplankton chlorophyll-a among taxa used Chemtax, an Shows Distribution of algorithm based on the mean ratios of photosynthetic pigments in each of a Picoplanktonic Pelagophyte a range of algal classes that allocates biomass to these classes based on their contribution to the overall How can we determine the distribution of uncultured marine microorganisms? pigmentation in a phytoplankton Targeted metagenomics has provided the complete chloroplast genome assemblage. For allocation to sequence, and the distribution, for a picoplanktonic pelagophyte alga. pelagophyceans it was assumed that light-harvesting carotenoid John A. Raven What is the Pelagophyceae? The 19’-butanoyloxofucoxanthin was class Pelagophyceae was erected unique to, and ubiquitous within, Determining the diversity, and the in 1997 to contain a number of the Pelagophyceae. The former functional significance, of marine small-celled heterokontophyte algae assumption may not be true [7], nor micro-organisms has been hampered united by molecular genetic, may the latter [2]. Granted the by our inability to culture and hence ultrastructural and (to a lesser extent) assumptions made, the characterise the majority of the photosynthetic pigments [2,3]. They Pelagophyceae contributed 4% to net microorganisms which have been are all marine and mainly planktonic, primary production and 4.7% to the isolated. Metagenomic studies using and include the organisms which have chlorophyll-a content of the the innovative technique of at-sea caused brown tides in the coastal phytoplankton from 4–8 metres depth. fluorescence activated cell sorting waters off the east coast of the USA 81% of the Pelagophyceae were less have allowed Worden et al. [1], (Aureococcus anophagefferens) than 5 mm in equivalent spherical as reported in this issue of Current and the Gulf of Mexico (Aureaumbra diameter [6]. Under the conditions of Biology, to construct a complete lagunensis), as well as the open ocean the observations, the specific growth chloroplast genome sequence for flagellate Pelagomonas calceolata and rate of the pelagophyceans was 0.87 a eukaryotic picoeukaryote from the coccoid Pelagococcus subviridis [2,3]. units cell mass increase per unit cell Gulf Stream Current. This technique They have been subject to significant mass per day, with an equal specific generates reference genome ecophysiological and genomic rate of grazing (i.e., no change information from abundant natural analysis [4,5]. in population size) [6]. The populations without the need for The work of Worden et al. [1] pelagophycean growth rate was close culturing. The organism containing the provides an excellent example of to that of the phytoplankton community sequenced chloroplast genome is a novel method of estimating the as a whole (i.e., 0.89 per day) [6]. a member of the genus Pelagomonas, distribution of an uncultured marine Studies of the (mainly eukaryotic) based on the 100% sequence similarity microorganism. Worden et al. [1] point phytoplankton with effective spherical of the rubisco (ribulose bisphosphate out that other methods of estimating diameters of less than 3 mm in the open carboxylase-oxygenase) large subunit the (quantitative) occurrence of ocean of the Arabian Sea using PCR of gene (rbcL) from the Gulf Stream pelagophyceans are less precise; 16S rRNA were biased toward organism with the partial sequences examples are the use of primer-based eukaryotic plastid sequences rather from cultured Pelagomonas calceolate molecular genetic and photosynthetic than cyanobacterial sequences [8]. [1]. Despite this complete sequence pigment analyses. Radioactive Granted the assumptions made (see similarity, Worden et al. [1] opted for inorganic carbon labelling of total cell [1]), pelagophyceans were 0–8% of the the cautious conclusion that the carbon and of pigments have been total at the depths examined (i.e., 10 uncultured population is ‘‘wild used to estimate the contribution of and 35 m at Station 1; 44 and 64 m at Pelagomonas’’ rather than the taxonomic groups of phytoplankton Station 2) [8]. Using FISH technology [9] plausible view that the organism from (identified by their pigment it was found that the Pelagophyceae the Gulf Stream is Pelagomonas composition) to net primary contribute 2 and 10% of eukaryotic calceolate, a member of the class productivity in the northwestern phytoplankton biomass with effective Pelagophyceae. Mediterranean [6]. The allocation of cell diameter less than and more than Dispatch R683 3 mm, respectively, along 7,500 km A biomarker restricted to the Kustka, A.B., et al. (2011). Niche of the harmful of the Atlantic Meridonal Transect Pelagophyceae has been used to show alga Aureococcus anophgefferens revealed through genomics. Proc. Natl. Acad. Sci. USA (19 N38 Wto39 S43W). both the age of the class and their 108, 4352–4357. Nair et al. [7] summarise methods by qualitative contribution to export 6. Latasa, M., Mora´ n, X.A.G., Scharel, R., and Estrada, M. (2005). Estimating the carbon flux which remote (satellite) sensing of production in the past. The sterol through main phytoplankton groups in the ocean-leaving radiation can establish 24-n-propylidenecholesterol was northwestern Mediterranean. Limnol. Oceanogr. 50, 1447–1458. the degree of flattening of the characteristic of the 42 strains 7. Nair, A., Sathyendranath, S., Platt, T., chlorophyll-a spectrum (package of Pelagopophyceae tested; this Morales, J., Stuart, V., Forget, M.-H., effect) and hence the size of the sterol has not been reported from Devred, E., and Boumann, H. (2008). Remote sensing of phytoplankton functional types. particles containing the chlorophyll elsewhere [15]. 24-n-propylcholestane, Remote Sensing Environm. 112, 3366–3375. [10–13]. While this method can partition the diagenetic derivative of 8. Fuller, N.J., Cambell, C., Allen, D.J., Pitt, F.D., Zwirglmaier, K., Le Gall, F., Vaulot, D., and phytoplankton into, for example, pico-, 24-n-propylidenecholesterol, is Scanlan, D.J. (2006). Analysis of photosynthetic nano- and micro-plankton size classes present in oils from the Neoproterozoic picoeukaryote diversity at open ocean sites in (respectively < 2 mm, 2–20 mm and (Cryogenian and Ediacaran) and Lower the Arabian Sea using a POCR biased towards marine algal protists. Aquat. Microbial. Ecol. 20–200 mm), it does not directly Cambrian [16]. This indicates both the 43, 79–93. establish the pigment signature of an presence of the Pelagophyceae and 9. Grob, C., Hartmann, M., Zubkov, M.V., and Scanlan, D.J. (2011). Invariable biomass-specific algal taxon. For the Pelagophyceae, their qualitative contribution to export primary production of taxonomically discrete such analyses establish the fraction of production, despite their small size and groups across the Atlantic Ocean. Environm. phytoplankton in the size range known the absence until the Middle Cambrian Microbiol. 13, 3266–3274. 10. Devred, E., Sathyendrenath, S., Stuart, V., to correspond to the Pelagophyceae, about 520 million years ago of Maas, H., Ulloa, O., and Platt, T. (2006). A but not the contribution of zooplankton grazers which could two-component model of phytoplankton absorption in the open ocean: theory and Pelagophyceae to that size class. produce large (hence rapidly sinking) applications. J. Geophys. Res. 111 http:// Export production removes sea faecal pellets, even if these relatively dx.doi.org/10.1029/2005KC002880. surface carbon dioxide to the deep large zooplankton could feed on the 11. Uitz, J., Claustre, H., Morel, A., and Hooker, S. (2006). Vertical distribution of phytoplankton ocean as organic carbon where, even very small pelagophycean cells. Kelly communities in open ocean: an assessment after respiration back to carbon et al. [16] note that green (chlorophyll-a) based on surface chlorophyll. J. Geophys. Res. 111 http://dx.doi.org/10.1029/2005JC003207. dioxide, the carbon is out of contact algae were much more quantitatively 12. Uitz, J., Claustre, H., Gentili, B., and with the atmosphere for hundreds of important in the steranes detected than Stramski, D. (2010). Phytoplankton