Cell size, photosynthesis and the package effect: an artificial selection approach

Malerba, Martino E., Palacios, Maria M., Palacios Delgado, Yussi M., Beardall, John, and Marshall, Dustin J. (2018) Cell size, photosynthesis and the package effect: an artificial selection approach. New Phytologist, 219 (1). pp. 449-461.

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Abstract

Cell size correlates with most traits among phytoplankton species. Theory predicts that larger cells should show poorer photosynthetic performance, perhaps due to reduced intracellular self-shading (i.e. package effect). Yet current theory relies heavily on interspecific correlational approaches and causal relationships between size and photosynthetic machinery have remained untested. As a more direct test, we applied 250 generations of artificial selection (c. 20 months) to evolve the green microalga Dunaliella teriolecta (Chlorophyta) toward different mean cell sizes, while monitoring all major photosynthetic parameters. Evolving larger sizes (> 1500% difference in volume) resulted in reduced oxygen production per chlorophyll molecule – as predicted by the package effect. However, large-evolved cells showed substantially higher rates of oxygen production – a finding unanticipated by current theory. In addition, volume-specific photosynthetic pigments increased with size (Chla+b), while photo-protectant pigments decreased (β-carotene). Finally, larger cells displayed higher growth performances and Fv/Fm, steeper slopes of rapid light curves (α) and smaller light-harvesting antennae (σPSII) with higher connectivity (ρ). Overall, evolving a common ancestor into different sizes showed that the photosynthetic characteristics of a species coevolves with cell volume. Moreover, our experiment revealed a trade-off between chlorophyll-specific (decreasing with size) and volume-specific (increasing with size) oxygen production in a cell.

Item ID: 58505
Item Type: Article (Research - C1)
ISSN: 1469-8137
Keywords: allometric size-scaling; artificial selection; evolutionary size-shift; experimental evolution; geometric biology; metabolism; oxygen evolution; primary production
Copyright Information: © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust
Funders: Australian Research Council (ARC)
Projects and Grants: ARC DP110103529
Date Deposited: 04 Jun 2019 21:26
FoR Codes: 31 BIOLOGICAL SCIENCES > 3105 Genetics > 310510 Molecular evolution @ 100%
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