Conspicuous chloroplast with light harvesting-photosystem I/II megacomplex in marine Prorocentrum cordatum

authored by

Jana Kalvelage, Lars Wöhlbrand, Jennifer Senkler, Julian Schumacher, Noah Ditz, Kai Bischof, Michael Winklhofer, Andreas Klingl, Hans-Peter Braun, Ralf Rabus

Abstract

Marine photosynthetic (micro)organisms drive multiple biogeochemical cycles and display a large diversity. Among them, the bloom-forming, free-living dinoflagellate Prorocentrum cordatum CCMP 1329 (formerly P. minimum) stands out with its distinct cell biological features. Here, we obtained insights into the structural properties of the chloroplast and the photosynthetic machinery of P. cordatum using microscopic and proteogenomic approaches. High-resolution FIB/SEM analysis revealed a single large chloroplast (∼40% of total cell volume) with a continuous barrel-like structure, completely lining the inner face of the cell envelope and enclosing a single reticular mitochondrium, the Golgi apparatus, as well as diverse storage inclusions. Enriched thylakoid membrane fractions of P. cordatum were comparatively analyzed with those of the well-studied model-species Arabidopsis (Arabidopsis thaliana) using 2D BN DIGE. Strikingly, P. cordatum possessed a large photosystem-light harvesting megacomplex (>1.5 MDa), which is dominated by photosystems I and II (PSI, PSII), chloroplast complex (CCI), and chlorophylla-b (chla-b) binding light harvesting complex proteins (LhcPs). This finding parallels the absence of grana in its chloroplast and distinguishes from the predominant separation of PSI and PSII complexes in A. thaliana, indicating a different mode of flux balancing. Except for the core elements of the ATP synthase and the cytb6f-complex, the composition of the other complexes (PSI, PSII, and pigment-binding proteins (PBPs)) of P. cordatum differed markedly from those of A. thaliana. Furthermore, a high number of PBPs was detected, accounting for a large share of the total proteomic data (∼65%) and potentially providing P. cordatum with flexible adaptation to changing light regimes.

Organisation(s)

Institute of Plant Genetics

External Organisation(s)

Jacobs University Bremen
Carl von Ossietzky University of Oldenburg
Ludwig-Maximilians-Universität München (LMU)

Type

Article

Journal

Plant physiology

ISSN

0032-0889

Publication date

08.02.2024

Publication status

E-pub ahead of print

Peer reviewed

Yes

Sustainable Development Goals

SDG 14 - Life Below Water

Electronic version(s)

https://doi.org/10.1093/plphys/kiae052 (Access: Open)