A novel type of light-harvesting antenna protein of red algal origin in algae with secondary plastidsReport as inadecuate

A novel type of light-harvesting antenna protein of red algal origin in algae with secondary plastids - Download this document for free, or read online. Document in PDF available to download.

* Corresponding author 1 Fachbereich Biologie Konstanz 2 Dept of Physiology and Plant Biochemistry 3 LIENSs - LIttoral ENvironnement et Sociétés - UMR 7266 4 CNRS - Centre National de la Recherche Scientifique

Abstract : Background: Light, the driving force of photosynthesis, can be harmful when present in excess; therefore, any light harvesting system requires photoprotection. Members of the extended light-harvesting complex LHC protein superfamily are involved in light harvesting as well as in photoprotection and are found in the red and green plant lineages, with a complex distribution pattern of subfamilies in the different algal lineages. Results: Here, we demonstrate that the recently discovered -red lineage chlorophyll a-b-binding-like proteins- RedCAPs form a monophyletic family within this protein superfamily. The occurrence of RedCAPs was found to be restricted to the red algal lineage, including red algae with primary plastids as well as cryptophytes, haptophytes and heterokontophytes with secondary plastids of red algal origin. Expression of a full-length RedCAP:GFP fusion construct in the diatom Phaeodactylum tricornutum confirmed the predicted plastid localisation of RedCAPs. Furthermore, we observed that similarly to the fucoxanthin chlorophyll a-c-binding light-harvesting antenna proteins also RedCAP transcripts in diatoms were regulated in a diurnal way at standard light conditions and strongly repressed at high light intensities. Conclusions: The absence of RedCAPs from the green lineage implies that RedCAPs evolved in the red lineage after separation from the the green lineage. During the evolution of secondary plastids, RedCAP genes therefore must have been transferred from the nucleus of the endocytobiotic alga to the nucleus of the host cell, a process that involved complementation with pre-sequences allowing import of the gene product into the secondary plastid bound by four membranes. Based on light-dependent transcription and on localisation data, we propose that RedCAPs might participate in the light intensity and quality-dependent structural or functional reorganisation of the light-harvesting antennae of the photosystems upon dark to light shifts as regularly experienced by diatoms in nature. Remarkably, in plastids of the red lineage as well as in green lineage plastids, the phycobilisome based cyanobacterial light harvesting system has been replaced by light harvesting systems that are based on members of the extended LHC protein superfamily, either for one of the photosystems PS I of red algae or for both diatoms. In their proposed function, the RedCAP protein family may thus have played a role in the evolutionary structural remodelling of light-harvesting antennae in the red lineage.

Keywords : Red lineage chlorophyll a-b-binding-like proteins Gene transfer Light-harvesting antenna proteins Complex plastids Diatoms Chloroplast

Author: Sabine Sturm - Johannes Engelken - Ansgar Gruber - Sascha Vugrinec - Peter G. Kroth - Iwona Adamska - Johann Lavaud -

Source: https://hal.archives-ouvertes.fr/


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