The chloroplast SRP systems of \(\textit {Chaetosphaeridium globosum}\) and \(\textit {Physcomitrella patens}\) as intermediates in the evolution of SRP-dependent protein transport in higher plants

  • The bacterial signal recognition particle (SRP) mediates the cotranslational targeting of membrane proteins and is a high affinity complex consisting of a SRP54 protein subunit (Ffh) and an SRP RNA. The chloroplast SRP (cpSRP) pathway has adapted throughout evolution to enable the posttranslational targeting of the light harvesting chlorophyll a/b binding proteins (LHCPs) to the thylakoid membrane. In spermatophytes (seed plants), the cpSRP lacks the SRP RNA and is instead formed by a high affinity interaction of the conserved 54-kD subunit (cpSRP54) with the chloroplast-specific cpSRP43 protein. This heterodimeric cpSRP recognizes LHCP and delivers it to the thylakoid membrane. However, in contrast to spermatophytes, plastid SRP RNAs were identified within all streptophyte lineages and in all chlorophyte branches. Furthermore, it was shown that cpSRP43 does not interact with cpSRP54 in chlorophytes (e.g., \(\textit {Chlamydomonas reinhardtii}\)). In this study, we biochemically characterized the cpSRP system of the charophyte \(\textit {Chaetosphaeridium globosum}\) and the bryophyte \(\textit {Physcomitrella patens}\). Interaction studies demonstrate low affinity binding of cpSRP54 to cpSRP43 (\(K_{d}\) ~10 \(\mu\)M) in \(\textit {Chaetosphaeridium globosum}\) and \(textit {Physcomitrella patens}\) as well as relatively low affinity binding of cpSRP54 to cpSRP RNA (\(K_{d}\) ~1 \(\mu\)M) in \(\textit {Physcomitrella patens}\). CpSRP54/cpSRP43 complex formation in charophytes is supported by the finding that specific alterations in the second chromodomain of cpSRP43, that are conserved within charophytes and absent in land plants, do not interfere with cpSRP54 binding. Furthermore, our data show that the elongated apical loop structure of the \(\textit {Physcomitrella patens}\) cpSRP RNA contributes to the low binding affinity between cpSRP54 and the cpSRP RNA.

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Metadaten
Author:Dominik ZieheGND, Beatrix DünschedeGND, Mira ZenkerGND, Silke FunkeGND, Marc Michael NowaczykORCiDGND, Danja SchünemannGND
URN:urn:nbn:de:hbz:294-73483
DOI:https://doi.org/10.1371/journal.pone.0166818
Parent Title (English):PLoS ONE
Publisher:Public Library of Science
Place of publication:San Francisco
Document Type:Article
Language:English
Date of Publication (online):2020/07/16
Date of first Publication:2016/11/18
Publishing Institution:Ruhr-Universität Bochum, Universitätsbibliothek
Volume:11
Issue:11, Artikel e0166818
First Page:e0166818-1
Last Page:e0166818-18
Institutes/Facilities:Lehrstuhl für Pflanzenphysiologie, Arbeitsgruppe Molekularbiologie pflanzlicher Organellen
Protein Research Department
open_access (DINI-Set):open_access
faculties:Fakultät für Biologie und Biotechnologie
Licence (English):License LogoCreative Commons - CC BY 4.0 - Attribution 4.0 International