Heterokont algae such as diatoms and the raphidophyte Heterosigma akashiwo and peridinin-containing dinoflagellates such as Heterocapsa triquetra originally acquired their chloroplasts via secondary endosymbiosis involving a red algal endosymbiont and a eukaryote host, resulting in ‘complex’ chloroplasts surrounded by four and three membranes, respectively. The precursors of both heterokont and dinoflagellate chloroplast-targeted proteins are first inserted into the ER with removal of an N-terminal signal peptide, but how they traverse the remaining membranes is unclear. Using a nuclear-encoded thylakoid lumen protein, PsbO, from the heterokont alga Heterosigma akashiwo, the dinoflagellate Heterocapsa triquetra and the red alga Porphyra yezoensis we show that precursors without the ER signal peptide can be imported into pea chloroplasts. In the case of the H. triquetra and Porphyra PsbO, the precursors were processed to their predicted mature size and localized within the thylakoid lumen, using the Sec-dependent pathway. We report for the first time a stromal processing peptidase (SPP) activity from an alga of the red lineage. The enzyme processes the Heterosigma PsbO precursor at a single site and appears to have different substrate and reaction specificities from the plant SPP. In spite of the fact that we could not find convincing homologs of the plant chloroplast import machinery in heterokont (diatom) and red algal genomes, it is clear that these three very different lines of algae use similar mechanisms to import chloroplast precursors.
Plant Molecular Biology – Springer Journals
Published: Dec 17, 2004
It’s your single place to instantly
discover and read the research
that matters to you.
Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.
All for just $49/month
Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly
Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.
All the latest content is available, no embargo periods.
“Whoa! It’s like Spotify but for academic articles.”@Phil_Robichaud