Limits...
The RUBISCO to Photosystem II Ratio Limits the Maximum Photosynthetic Rate in Picocyanobacteria.

Zorz JK, Allanach JR, Murphy CD, Roodvoets MS, Campbell DA, Cockshutt AM - Life (Basel) (2015)

Bottom Line: Marine Synechococcus and Prochlorococcus are picocyanobacteria predominating in subtropical, oligotrophic marine environments, a niche predicted to expand with climate change.When grown under common low light conditions Synechococcus WH 8102 and Prochlorococcus MED 4 show similar Cytochrome b6f and Photosystem I contents normalized to Photosystem II content, while Prochlorococcus MIT 9313 has twice the Cytochrome b6f content and four times the Photosystem I content of the other strains.Photosystem II electron transport capacity is highly correlated to the molar ratio of RUBISCO active sites to Photosystem II but not to the ratio of cytochrome b6f to Photosystem II, nor to the ratio of Photosystem I: Photosystem II.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry & Biochemistry, Mount Allison University, Sackville, New Brunswick, E4L 1G8, Canada. jkzorz@mta.ca.

ABSTRACT
Marine Synechococcus and Prochlorococcus are picocyanobacteria predominating in subtropical, oligotrophic marine environments, a niche predicted to expand with climate change. When grown under common low light conditions Synechococcus WH 8102 and Prochlorococcus MED 4 show similar Cytochrome b6f and Photosystem I contents normalized to Photosystem II content, while Prochlorococcus MIT 9313 has twice the Cytochrome b6f content and four times the Photosystem I content of the other strains. Interestingly, the Prochlorococcus strains contain only one third to one half of the RUBISCO catalytic subunits compared to the marine Synechococcus strain. The maximum Photosystem II electron transport rates were similar for the two Prochlorococcus strains but higher for the marine Synechococcus strain. Photosystem II electron transport capacity is highly correlated to the molar ratio of RUBISCO active sites to Photosystem II but not to the ratio of cytochrome b6f to Photosystem II, nor to the ratio of Photosystem I: Photosystem II. Thus, the catalytic capacity for the rate-limiting step of carbon fixation, the ultimate electron sink, appears to limit electron transport rates. The high abundance of Cytochrome b6f and Photosystem I in MIT 9313, combined with the slower flow of electrons away from Photosystem II and the relatively low level of RUBISCO, are consistent with cyclic electron flow around Photosystem I in this strain.

No MeSH data available.


Related in: MedlinePlus

Molar ratios of representative protein subunits PsaC:PsbA (PSI:PSII, circles); PetC:PsbA (Cytb6f complex:PSII, squares); and PsbD: PsbA (PSII:PSII, triangles) over time in cultures of Prochlorococcus MIT 9313. n = 6 independent determinations, ± SEM.
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life-05-00403-f001: Molar ratios of representative protein subunits PsaC:PsbA (PSI:PSII, circles); PetC:PsbA (Cytb6f complex:PSII, squares); and PsbD: PsbA (PSII:PSII, triangles) over time in cultures of Prochlorococcus MIT 9313. n = 6 independent determinations, ± SEM.

Mentions: Figure 1 shows the molar ratios of PSI:PSII, cytochrome b6f:PSII and RUBISCO:PSII in Prochlorococcus marinus MIT 9313 with days in culture following a one in four dilution of the culture into fresh Pro99 medium. The PSI:PSII ratio nearly doubled over the first five days in culture, and then declined. Over this period the quantum yield of PSII (FV/FM) did not change (data not shown). For consistency, all subsequent measurements were conducted on cells three to four days post dilution; after two to three days of exponential growth.


The RUBISCO to Photosystem II Ratio Limits the Maximum Photosynthetic Rate in Picocyanobacteria.

Zorz JK, Allanach JR, Murphy CD, Roodvoets MS, Campbell DA, Cockshutt AM - Life (Basel) (2015)

Molar ratios of representative protein subunits PsaC:PsbA (PSI:PSII, circles); PetC:PsbA (Cytb6f complex:PSII, squares); and PsbD: PsbA (PSII:PSII, triangles) over time in cultures of Prochlorococcus MIT 9313. n = 6 independent determinations, ± SEM.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390859&req=5

life-05-00403-f001: Molar ratios of representative protein subunits PsaC:PsbA (PSI:PSII, circles); PetC:PsbA (Cytb6f complex:PSII, squares); and PsbD: PsbA (PSII:PSII, triangles) over time in cultures of Prochlorococcus MIT 9313. n = 6 independent determinations, ± SEM.
Mentions: Figure 1 shows the molar ratios of PSI:PSII, cytochrome b6f:PSII and RUBISCO:PSII in Prochlorococcus marinus MIT 9313 with days in culture following a one in four dilution of the culture into fresh Pro99 medium. The PSI:PSII ratio nearly doubled over the first five days in culture, and then declined. Over this period the quantum yield of PSII (FV/FM) did not change (data not shown). For consistency, all subsequent measurements were conducted on cells three to four days post dilution; after two to three days of exponential growth.

Bottom Line: Marine Synechococcus and Prochlorococcus are picocyanobacteria predominating in subtropical, oligotrophic marine environments, a niche predicted to expand with climate change.When grown under common low light conditions Synechococcus WH 8102 and Prochlorococcus MED 4 show similar Cytochrome b6f and Photosystem I contents normalized to Photosystem II content, while Prochlorococcus MIT 9313 has twice the Cytochrome b6f content and four times the Photosystem I content of the other strains.Photosystem II electron transport capacity is highly correlated to the molar ratio of RUBISCO active sites to Photosystem II but not to the ratio of cytochrome b6f to Photosystem II, nor to the ratio of Photosystem I: Photosystem II.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry & Biochemistry, Mount Allison University, Sackville, New Brunswick, E4L 1G8, Canada. jkzorz@mta.ca.

ABSTRACT
Marine Synechococcus and Prochlorococcus are picocyanobacteria predominating in subtropical, oligotrophic marine environments, a niche predicted to expand with climate change. When grown under common low light conditions Synechococcus WH 8102 and Prochlorococcus MED 4 show similar Cytochrome b6f and Photosystem I contents normalized to Photosystem II content, while Prochlorococcus MIT 9313 has twice the Cytochrome b6f content and four times the Photosystem I content of the other strains. Interestingly, the Prochlorococcus strains contain only one third to one half of the RUBISCO catalytic subunits compared to the marine Synechococcus strain. The maximum Photosystem II electron transport rates were similar for the two Prochlorococcus strains but higher for the marine Synechococcus strain. Photosystem II electron transport capacity is highly correlated to the molar ratio of RUBISCO active sites to Photosystem II but not to the ratio of cytochrome b6f to Photosystem II, nor to the ratio of Photosystem I: Photosystem II. Thus, the catalytic capacity for the rate-limiting step of carbon fixation, the ultimate electron sink, appears to limit electron transport rates. The high abundance of Cytochrome b6f and Photosystem I in MIT 9313, combined with the slower flow of electrons away from Photosystem II and the relatively low level of RUBISCO, are consistent with cyclic electron flow around Photosystem I in this strain.

No MeSH data available.


Related in: MedlinePlus