Phycoerythrin is absent from the pyrenoid of Porphyridium cruentum: photosynthetic implications

Document Type

Article

Publication Date

1-1-1990

Publication Title

Planta

Volume

180

Issue

2

First Page

249

Keywords

Photosystem I, II Porphyridium, Phycobiliprotein, Pyrenoid, Rhodophyta, Ribulose-1, 5-bisphosphate carboxylase/oxygenase

Last Page

256

Abstract

The thylakoid lamellae which traverse the pyrenoid of the unicellular red alga Porphyridium cruentum (Agardh) Nägeli appear to lack phycobilisomes. We have confirmed by immuno-electron microscopy that phycoerythrin (PE), an important structural component of the phycobilisomes of red algae, is absent from the pyrenoid. To characterize pyrenoid thylakoids further, electron-microscopic cytochemical methods were employed to detect photosystem activity. Photosystem (PS) I activity was demonstrated in both stromal and pyrenoid thylakoids by the photooxidation of 3,3′-diaminobenzidine. In contrast, the localization of photoreduced distyryl nitroblue tetrazolium demonstrated that PSII activity was restricted to stromal thylakoids. The observed partitioning of PE and PSII activity within the plastid may be related to another observation, that being the localization of nearly all ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) within the pyrenoid of this alga. It is possible that the pyrenoid of P. cruentum functions as a specific metabolic compartment where CO2 fixation is enhanced by the absence of photosynthetic O2 evolution. © 1990 Springer-Verlag.

DOI

10.1007/BF00194004

ISSN

00320935

E-ISSN

14322048

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