Journal Article

A common partitioning strategy for photosynthetic products in evolutionarily distinct phytoplankton species

Robert T. O'Malley, Kimberly H. Halsey, Jason R. Graff, Allen J. Milligan, Michael J. Behrenfeld

2013

Overview

We compare the nutrient-dependent photosynthetic efficiencies of the chlorophyte, Dunaliella tertiolecta, with those of the marine diatom, Thalassiosira weissflogii. Despite considerable evolutionary and physiological differences, these two species appear to use nearly identical growth strategies under a wide range of nutrient limitation. Using a variety of physiological measurements, we find that, for both species and across all growth rates, 75% of the gross photosynthetic electron flow is invested in carbon fixation and only 30% is retained as net carbon accumulation. A majority of gross photosynthesis (70%) is ultimately used as reductant for biosynthetic pathways and for the generation of ATP. In both species, newly formed carbon products exhibit much shorter half-lives at slow growth rates than at fast growth rates. We show that this growth rate dependence is a result of increased polysaccharide storage during the S phase of the cell cycle. We present a model of carbon utilization that incorporates this growth rate-dependent carbon allocation and accurately captures (r 2 = 0.94) the observed time-resolved carbon retention. Together, our findings suggest a common photosynthetic optimization strategy in evolutionarily distinct phytoplankton species and contribute towards a systems-level understanding of carbon flow in photoautotrophs.

• Publisher: New Phytologist Trust,Wiley Subscription Services, Inc
• Subject: Absorption / algae / ATP / Autotrophic Processes - drug effects / autotrophs / Bacillariophyceae / Biological Evolution / biosynthesis / Carbon / carbon allocation / Carbon allocations / carbon assimilation / Carbon cycle / Carbon Cycle - drug effects / carbon dioxide fixation / Carbon fixation / Cell cycle / Cell Cycle - drug effects / Cell growth / Chlorophylls / Diatoms / Dunaliella / Dunaliella tertiolecta / Evolution / growth optimization metabolism / Growth rate / half life / interphase / Mineral nutrients / Nitrates - pharmacology / Nutrients / Optimization / Photosynthesis / Photosynthesis - drug effects / Physiology / Phytoplankton / Phytoplankton - drug effects / Phytoplankton - growth & development / Phytoplankton - physiology / Plankton / Plant growth / Polysaccharides / primary production / Reducing agents / S phase / Species / Storage / Thalassiosira / Thalassiosira weissflogii