Phycoerythrin Association with Photosystem II in the Cryptophyte Alga Rhodomonas salina

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I. N. Stadnichuk^1,a*, T. M. Novikova², G. S. Miniuk², V. A. Boichenko^3#, Yu. V. Bolychevtseva⁴, E. S. Gusev¹, and E. P. Lukashev⁵

¹Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, 127726 Moscow, Russia

²Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, 119071 Moscow, Russia

³Institute of Fundamental Problems of Biology of the Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia

⁴Kovalevski Institute of Biology of the Southern Seas, Russian Academy of Sciences, 299011 Sevastopol, Russia

⁵Lomonosov Moscow State University, Faculty of Biology, 119991 Moscow, Russia

^* To whom correspondence should be addressed.

^# Deceased.

Received April 9, 2020; Revised May 2, 2020; Accepted May 3, 2020

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Cryptophyte algae belong to a special group of oxygenic photosynthetic organisms containing pigment combination unique for plastids – phycobiliproteins and chlorophyll a/c-containing antenna. Despite the progress in investigation of morphological and ecological features, as well as genome-based systematics of cryptophytes, their photosynthetic apparatus remains poorly understood. The ratio of the photosystems (PS)s I and II is unknown and information on participation of the two antennal complexes in functions of the two photosystems is inconsistent. In the present work we demonstrated for the first time that the cryptophyte alga Rhodomonas salina had the PSI to PSII ratio in thylakoid membranes equal to 1 : 4, whereas this ratio in cyanobacteria and higher plants was known to be 3 : 1 and 1 : 1, respectively. Furthermore, it was established that contrary to the case of cyanobacteria the phycobiliprotein antenna represented by phycoerythrin-545 (PE-545) in R. salina was associated only with the PSII, which indicated specific spatial organization of these protein pigments within the thylakoids that did not facilitate interaction with the PSI.

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KEY WORDS: cryptophytes, phycobiliproteins, phycoerythrin, chlorophyll a, chlorophyll c, photosystem I, photosystem II

DOI: 10.1134/S000629792006005X

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