The role of Rubisco kinetics and pyrenoid morphology in shaping the CCM of haptophyte microalgae

The haptophyte algae are a cosmopolitan group of primary producers that contribute significantly to the marine carbon cycle and play a major role in paleo-climate studies. Despite their global importance, little is known about carbon assimilation in haptophytes, in particular the kinetics of their F...

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Bibliographic Details
Published in:Journal of experimental botany 2017-06, Vol.68 (14), p.3959-3969
Main Authors: Heureux, Ana M.C., Young, Jodi N., Whitney, Spencer M., Eason-Hubbard, Maeve R., Lee, Renee B.Y., Sharwood, Robert E., Rickaby, Rosalind E.M.
Format: Article
Language:English
Subjects:
Chloroplasts - metabolism
Haptophyta - enzymology
Haptophyta - metabolism
Kinetics
Microalgae - enzymology
Microalgae - metabolism
Photosynthesis
RESEARCH PAPER
Research Papers
Ribulose-Bisphosphate Carboxylase - metabolism
Species Specificity
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Summary:The haptophyte algae are a cosmopolitan group of primary producers that contribute significantly to the marine carbon cycle and play a major role in paleo-climate studies. Despite their global importance, little is known about carbon assimilation in haptophytes, in particular the kinetics of their Form 1D CO₂-fixing enzyme, Rubisco. Here we examine Rubisco properties of three haptophytes with a range of pyrenoid morphologies (Pleurochrysis carterae, Tisochrysis lutea, and Pavlova lutheri) and the diatom Phaeodactylum tricornutum that exhibit contrasting sensitivities to the trade-offs between substrate affinity (K m) and turnover rate (k cat) for both CO₂ and O₂. The pyrenoid-containing T. lutea and P. carterae showed lower Rubisco content and carboxylation properties (K C and k C cat) comparable with those of Form 1D-containing non-green algae. In contrast, the pyrenoid-lacking P. lutheri produced Rubisco in 3-fold higher amounts, and displayed a Form 1B Rubisco k C cat–K C relationship and increased CO₂/O₂ specificity that, when modeled in the context of a C₃ leaf, supported equivalent rates of photosynthesis to higher plant Rubisco. Correlation between the differing Rubisco properties and the occurrence and localization of pyrenoids with differing intracellular CO₂:O₂ microenvironments has probably influenced the divergent evolution of Form 1B and 1D Rubisco kinetics.
ISSN:0022-0957
1460-2431
DOI:10.1093/jxb/erx179