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Characterization of the influence of chlororespiration on the regulation of photosynthesis in the glaucophyte Cyanophora paradoxa

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ABSTRACT

Glaucophytes are primary symbiotic algae with unique plastids called cyanelles, whose structure is most similar to ancestral cyanobacteria among plastids in photosynthetic organisms. Here we compare the regulation of photosynthesis in glaucophyte with that in cyanobacteria in the aim of elucidating the changes caused by the symbiosis in the interaction between photosynthetic electron transfer and other metabolic pathways. Chlorophyll fluorescence measurements of the glaucophyte Cyanophora paradoxa NIES-547 indicated that plastoquinone (PQ) pool in photosynthetic electron transfer was reduced in the dark by chlororespiration. The levels of nonphotochemical quenching of chlorophyll fluorescence was high in the dark but decreased under low light, and increased again under high light. This type of concave light dependence was quite similar to that observed in cyanobacteria. Moreover, the addition of ionophore hardly affected nonphotochemical quenching, suggesting state transition as a main component of the regulatory system in C. paradoxa. These results suggest that cyanelles of C. paradoxa retain many of the characteristics observed in their ancestral cyanobacteria. From the viewpoint of metabolic interactions, C. paradoxa is the primary symbiotic algae most similar to cyanobacteria than other lineages of photosynthetic organisms.

No MeSH data available.


Related in: MedlinePlus

Red actinic light (peak at 660 nm) dependence of NPQ in C. paradoxa (black filled circles) and Synechocystis sp. PCC 6803 (open circles) at room temperature and white light dependence of state transition (red filled circles, corresponding to right vertical axis) estimated by the ratio of PSI fluorescence (725 nm) to PSII fluorescence (695 nm) determined at 77 K.Averages of at least three independent cultures are presented respectively and vertical bars indicate standard deviation.
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f3: Red actinic light (peak at 660 nm) dependence of NPQ in C. paradoxa (black filled circles) and Synechocystis sp. PCC 6803 (open circles) at room temperature and white light dependence of state transition (red filled circles, corresponding to right vertical axis) estimated by the ratio of PSI fluorescence (725 nm) to PSII fluorescence (695 nm) determined at 77 K.Averages of at least three independent cultures are presented respectively and vertical bars indicate standard deviation.

Mentions: In the case of cyanobacteria, not only blue light that preferentially excites PSI but also weak white or red light that excites both PSI and PSII are known to oxidize PQ pool. Since illumination by higher light reduces the PQ pool, NPQ values are high in the dark as well as under high light but low under growth light condition, resulting in the concave dependence on actinic light intensity8. This concave dependence of NPQ is observed in a wide range of cyanobacteria20, including a model cyanobacterium Synechocystis sp. PCC6803 (Fig. 3, open circles). We found that glaucophyte shows similar light dependence of NPQ (Fig. 3). When red actinic light was used, the levels of NPQ of glaucophyte cells were high in the dark and under high light, with minimum NPQ values around the actinic light at 31.5 μmol m−2 s−1 (Fig. 3, black filled circles). Under red actinic light, the main component of NPQ in cyanobacteria is shown to be state transition820. This seems to be also true for glaucophytes, since similar concave change was observed for the actinic light dependence of state transition estimated by relative chlorophyll fluorescence of PSI to that of PSII (F725/F695) determined at 77 K upon phycocyanin excitation (Fig. 3, red filled circles).


Characterization of the influence of chlororespiration on the regulation of photosynthesis in the glaucophyte Cyanophora paradoxa
Red actinic light (peak at 660 nm) dependence of NPQ in C. paradoxa (black filled circles) and Synechocystis sp. PCC 6803 (open circles) at room temperature and white light dependence of state transition (red filled circles, corresponding to right vertical axis) estimated by the ratio of PSI fluorescence (725 nm) to PSII fluorescence (695 nm) determined at 77 K.Averages of at least three independent cultures are presented respectively and vertical bars indicate standard deviation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384210&req=5

f3: Red actinic light (peak at 660 nm) dependence of NPQ in C. paradoxa (black filled circles) and Synechocystis sp. PCC 6803 (open circles) at room temperature and white light dependence of state transition (red filled circles, corresponding to right vertical axis) estimated by the ratio of PSI fluorescence (725 nm) to PSII fluorescence (695 nm) determined at 77 K.Averages of at least three independent cultures are presented respectively and vertical bars indicate standard deviation.
Mentions: In the case of cyanobacteria, not only blue light that preferentially excites PSI but also weak white or red light that excites both PSI and PSII are known to oxidize PQ pool. Since illumination by higher light reduces the PQ pool, NPQ values are high in the dark as well as under high light but low under growth light condition, resulting in the concave dependence on actinic light intensity8. This concave dependence of NPQ is observed in a wide range of cyanobacteria20, including a model cyanobacterium Synechocystis sp. PCC6803 (Fig. 3, open circles). We found that glaucophyte shows similar light dependence of NPQ (Fig. 3). When red actinic light was used, the levels of NPQ of glaucophyte cells were high in the dark and under high light, with minimum NPQ values around the actinic light at 31.5 μmol m−2 s−1 (Fig. 3, black filled circles). Under red actinic light, the main component of NPQ in cyanobacteria is shown to be state transition820. This seems to be also true for glaucophytes, since similar concave change was observed for the actinic light dependence of state transition estimated by relative chlorophyll fluorescence of PSI to that of PSII (F725/F695) determined at 77 K upon phycocyanin excitation (Fig. 3, red filled circles).

View Article: PubMed Central - PubMed

ABSTRACT

Glaucophytes are primary symbiotic algae with unique plastids called cyanelles, whose structure is most similar to ancestral cyanobacteria among plastids in photosynthetic organisms. Here we compare the regulation of photosynthesis in glaucophyte with that in cyanobacteria in the aim of elucidating the changes caused by the symbiosis in the interaction between photosynthetic electron transfer and other metabolic pathways. Chlorophyll fluorescence measurements of the glaucophyte Cyanophora paradoxa NIES-547 indicated that plastoquinone (PQ) pool in photosynthetic electron transfer was reduced in the dark by chlororespiration. The levels of nonphotochemical quenching of chlorophyll fluorescence was high in the dark but decreased under low light, and increased again under high light. This type of concave light dependence was quite similar to that observed in cyanobacteria. Moreover, the addition of ionophore hardly affected nonphotochemical quenching, suggesting state transition as a main component of the regulatory system in C. paradoxa. These results suggest that cyanelles of C. paradoxa retain many of the characteristics observed in their ancestral cyanobacteria. From the viewpoint of metabolic interactions, C. paradoxa is the primary symbiotic algae most similar to cyanobacteria than other lineages of photosynthetic organisms.

No MeSH data available.


Related in: MedlinePlus