Journal Article

Absence of Lutein, Violaxanthin and Neoxanthin Affects the Functional Chlorophyll Antenna Size of Photosystem-II but not that of Photosystem-I in the Green Alga <i>Chlamydomonas reinhardtii</i>

Juergen E. W. Polle, Krishna K. Niyogi and Anastasios Melis

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 42, issue 5, pages 482-491
Published in print May 2001 | ISSN: 0032-0781
Published online May 2001 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pce058
Absence of Lutein, Violaxanthin and Neoxanthin Affects the
Functional Chlorophyll Antenna Size of Photosystem-II but not that of
Photosystem-I in the Green Alga Chlamydomonas
reinhardtii

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Chlamydomonas reinhardtii double mutant npq2 lor1 lacks the β,ε-carotenoids lutein and loroxanthin as well as all β,β-epoxycarotenoids derived from zeaxanthin (e.g. violaxanthin and neoxanthin). Thus, the only carotenoids present in the thylakoid membranes of the npq2 lor1 cells are β-carotene and zeaxanthin. The effect of these mutations on the photochemical apparatus assembly and function was investigated. In cells of the mutant strain, the content of photosystem-II (PSII) and photosystem-I (PSI) was similar to that of the wild type, but npq2 lor1 had a significantly smaller PSII light-harvesting Chl antenna size. In contrast, the Chl antenna size of PSI was not truncated in the mutant. SDS-PAGE and Western blot analysis qualitatively revealed the presence of all LHCII and LHCI apoproteins in the thylakoid membrane of the mutant. The results showed that some of the LHCII and most of the LHCI were assembled and functionally connected with PSII and PSI, respectively. Photon conversion efficiency measurements, based on the initial slope of the light-saturation curve of photosynthesis and on the yield of Chl a fluorescence in vivo, showed similar efficiencies. However, a significantly greater light intensity was required for the saturation of photosynthesis in the mutant than in the wild type. It is concluded that zeaxanthin can successfully replace lutein and violaxanthin in most of the functional light-harvesting antenna of the npq2 lor1 mutant.

Keywords: Key words: Carotenoid mutant — Chlamydomonas reinhardtii — Chlorophyll antenna size — Light-harvesting proteins — Photosynthesis — Photosynthetic capacity.; Abbreviations: Car, carotenoids; CP24, CP26 and CP29, Chl-proteins 24, 26 and 29; LHCI and LHCII, light harvesting complex of PSI and PSII, respectively; PMSF, phenymethylsulfonylfluoride.

Journal Article.  7305 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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