TY  - JOUR
A1  - Felsner, Gregor
A1  - Sommer, Maik Sascha
A1  - Grünheit, Nicole
A1  - Hempel, Franziska
A1  - Moog, Daniel
A1  - Zauner, Stefan
A1  - Martin, William
A1  - Maier, Uwe G.
T1  - ERAD components in organisms with complex red plastids suggest recruitment of a preexisting protein transport pathway for the periplastid membrane
T2  - Genome biology and evolution
N2  - The plastids of cryptophytes, haptophytes, and heterokontophytes (stramenopiles) (together once known as chromists) are surrounded by four membranes, reflecting the origin of these plastids through secondary endosymbiosis. They share this trait with apicomplexans, which are alveolates, the plastids of which have been suggested to stem from the same secondary symbiotic event and therefore form a phylogenetic clade, the chromalveolates. The chromists are quantitatively the most important eukaryotic contributors to primary production in marine ecosystems. The mechanisms of protein import across their four plastid membranes are still poorly understood. Components of an endoplasmic reticulum-associated degradation (ERAD) machinery in cryptophytes, partially encoded by the reduced genome of the secondary symbiont (the nucleomorph), are implicated in protein transport across the second outermost plastid membrane. Here, we show that the haptophyte Emiliania huxleyi, like cryptophytes, stramenopiles, and apicomplexans, possesses a nuclear-encoded symbiont-specific ERAD machinery (SELMA, symbiont-specific ERAD-like machinery) in addition to the host ERAD system, with targeting signals that are able to direct green fluorescent protein or yellow fluorescent protein to the predicted cellular localization in transformed cells of the stramenopile Phaeodactylum tricornutum. Phylogenies of the duplicated ERAD factors reveal that all SELMA components trace back to a red algal origin. In contrast, the host copies of cryptophytes and haptophytes associate with the green lineage to the exclusion of stramenopiles and alveolates. Although all chromalveolates with four membrane-bound plastids possess the SELMA system, this has apparently not arisen in a single endosymbiotic event. Thus, our data do not support the chromalveolate hypothesis. Key words: Emiliania huxleyi, secondary endosymbiosis, chromalveolate, hypothesis, complex plastid, plastid protein import, algal evolution
KW  - emiliania huxleyi
KW  - secondary endosymbiosis
KW  - chromalveolate
KW  - hypothesis
KW  - complex plastid
KW  - plastid protein import
KW  - algal evolution
Y1  - 2010
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/22409
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30-106464
N1  - © The Author(s) 2010. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.5), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
VL  - 3
SP  - 140
EP  - 150
ER  -