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- Funk, Christiane, et al.
(författare)
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High-light stress and the one-helix LHC-like proteins of the cryptophyte Guillardia theta
- 2011
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Ingår i: Biochimica et Biophysica Acta - Bioenergetics. - : Elsevier BV. - 0005-2728 .- 1879-2650. ; 1807:7, s. 841-846
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Tidskriftsartikel (refereegranskat)abstract
- Cryptophytes like the cryptomonad Guillardia theta are part of the marine phytoplankton and therefore major players in global carbon and biogeochemical cycles. Despite the importance for the cell in being able to cope with large changes in illumination on a daily basis, very little is known about photoprotection mechanisms in cryptophytes. Here we show that G. theta is able to perform non-photochemical quenching, although none of the usual xanthophyll cycle pigments (e.g. zeaxanthin, diadinoxanthin, diatoxanthin) are present at detectable levels. Instead, acclimation to high light intensity seems to involve an increase of alloxanthin. G. theta has genes for two one-helix "light-harvesting-like" proteins, related to some cyanobacterial genes which are induced in response to high light stress. Both the plastid-encoded gene (hlipP) and the nucleomorph-encoded gene (HlipNm) are expressed, but transcript levels decrease rather than increase during high light exposure, suggesting they are not involved in a high light stress response. The HlipNm protein was detected with a specific antibody; expression was constant, independent of the light exposure.
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| 2. |
- Huesgen, Pitter F., et al.
(författare)
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Proteomic Amino-Termini Profiling Reveals Targeting Information for Protein Import into Complex Plastids
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:9, s. e74483-
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Tidskriftsartikel (refereegranskat)abstract
- In organisms with complex plastids acquired by secondary endosymbiosis from a photosynthetic eukaryote, the majority of plastid proteins are nuclear-encoded, translated on cytoplasmic ribosomes, and guided across four membranes by a bipartite targeting sequence. In-depth understanding of this vital import process has been impeded by a lack of information about the transit peptide part of this sequence, which mediates transport across the inner three membranes. We determined the mature N-termini of hundreds of proteins from the model diatom Thalassiosira pseudonana, revealing extensive N-terminal modification by acetylation and proteolytic processing in both cytosol and plastid. We identified 63 mature N-termini of nucleus-encoded plastid proteins, deduced their complete transit peptide sequences, determined a consensus motif for their cleavage by the stromal processing peptidase, and found evidence for subsequent processing by a plastid methionine aminopeptidase. The cleavage motif differs from that of higher plants, but is shared with other eukaryotes with complex plastids.
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