Scientific Publications
The conserved protein CBA1 is required for vitamin B12 uptake in different algal lineages.
Plant Physiol. 21:kiad564. doi: 10.1093/plphys/kiad564.
Microalgae play an essential role in global net primary productivity and global biogeochemical cycling. Despite their phototrophic
lifestyle, over half of algal species depend for growth on acquiring an external supply of the corrinoid vitamin B12
(cobalamin), a micronutrient produced only by a subset of prokaryotic organisms. Previous studies have identified protein
components involved in vitamin B12 uptake in bacterial species and humans. However, little is known about its uptake in algae.
Here, we demonstrate the essential role of a protein, cobalamin acquisition protein 1 (CBA1), in B12 uptake in Phaeodactylum
tricornutum using CRISPR-Cas9 to generate targeted knockouts and in Chlamydomonas reinhardtii by insertional mutagenesis.
In both cases, CBA1 knockout lines could not take up exogenous vitamin B12. Complementation of the C. reinhardtii mutants
with the wild-type CBA1 gene restored B12 uptake, and regulation of CBA1 expression via a riboswitch element enabled control
of the phenotype. When visualized by confocal microscopy, a YFP-fusion with C. reinhardtii CBA1 showed association with
membranes. Bioinformatics analysis found that CBA1-like sequences are present in all major eukaryotic phyla. In algal taxa,
the majority that encoded CBA1 also had genes for B12-dependent enzymes, suggesting CBA1 plays a conserved role. Our results
thus provide insight into the molecular basis of algal B12 acquisition, a process that likely underpins many interactions in
aquatic microbial communities.
Plant Physiol. 21:kiad564. doi: 10.1093/plphys/kiad564.
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