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Partially dissecting the steady-state electron fluxes in Photosystem I in wild-type and pgr5 and ndh mutants of Arabidopsis.

Kou J, Takahashi S, Fan DY, Badger MR, Chow WS - Front Plant Sci (2015)

Bottom Line: We obtained the linear electron flux (LEFO2) through both photosystems and the total electron flux through PS I (ETR1) in Arabidopsis in CO2-enriched air.ΔFlux = ETR1 - LEFO2 is an upper estimate of CEF, which consists of two components, an antimycin A-sensitive, PGR5 (proton gradient regulation 5 protein)-dependent component and an insensitive component facilitated by a chloroplastic nicotinamide adenine dinucleotide dehydrogenase-like complex (NDH).Using wild type as well as pgr5 and ndh mutants, we observed that (1) 40% of the absorbed light was partitioned to PS I; (2) at high irradiance a substantial antimycin A-sensitive CEF occurred in the wild type and the ndh mutant; (3) at low irradiance a sizable antimycin A-sensitive CEF occurred in the wild type but not in the ndh mutant, suggesting an enhancing effect of NDH in low light; and (4) in the pgr5 mutant, and the wild type and ndh mutant treated with antimycin A, a residual ΔFlux existed at high irradiance, attributable to charge recombination and/or pseudo-cyclic electron flow.

View Article: PubMed Central - PubMed

Affiliation: College of Animal Science and Technology, Northwest A&F University Yangling, China ; Division of Plant Sciences, Research School of Biology, The Australian National University Canberra, ACT, Australia.

ABSTRACT
Cyclic electron flux (CEF) around Photosystem I (PS I) is difficult to quantify. We obtained the linear electron flux (LEFO2) through both photosystems and the total electron flux through PS I (ETR1) in Arabidopsis in CO2-enriched air. ΔFlux = ETR1 - LEFO2 is an upper estimate of CEF, which consists of two components, an antimycin A-sensitive, PGR5 (proton gradient regulation 5 protein)-dependent component and an insensitive component facilitated by a chloroplastic nicotinamide adenine dinucleotide dehydrogenase-like complex (NDH). Using wild type as well as pgr5 and ndh mutants, we observed that (1) 40% of the absorbed light was partitioned to PS I; (2) at high irradiance a substantial antimycin A-sensitive CEF occurred in the wild type and the ndh mutant; (3) at low irradiance a sizable antimycin A-sensitive CEF occurred in the wild type but not in the ndh mutant, suggesting an enhancing effect of NDH in low light; and (4) in the pgr5 mutant, and the wild type and ndh mutant treated with antimycin A, a residual ΔFlux existed at high irradiance, attributable to charge recombination and/or pseudo-cyclic electron flow. Therefore, in low-light-acclimated plants exposed to high light, ΔFlux has contributions from various paths of electron flow through PS I.

No MeSH data available.


Related in: MedlinePlus

The difference between ΔFlux in the absence of antimycin (-AA) and the presence of antimycin A (+AA), representing an underestimate of the component of CEF inhibitable by antimycin A, is plotted against irradiance. The data are derived from Figures 1A and 2A for the wild type and from Figures 5A and 6A for the ndh mutant.
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Figure 7: The difference between ΔFlux in the absence of antimycin (-AA) and the presence of antimycin A (+AA), representing an underestimate of the component of CEF inhibitable by antimycin A, is plotted against irradiance. The data are derived from Figures 1A and 2A for the wild type and from Figures 5A and 6A for the ndh mutant.

Mentions: It may be instructive to estimate the magnitude of the antimycin A-sensitive component of ETR1. In the case of the wild type, the presence of antimycin A (+AA) gave a residual ΔFlux+AA that is in general contributed by charge recombination, pseudo-cyclic electron flow and, possibly, the NDH-dependent cyclic flux (Figure 2A). Subtracting ΔFlux+AA (Figure 2A) from ΔFlux-AA (Figure 1A) gives an estimate of the antimycin A-sensitive component of ETR1. However, (ΔFlux+AA - ΔFlux-AA) is an underestimate, since in the absence of antimycin A, the contributions from charge recombination and pseudo-cyclic electron flow could well have been smaller because of competition from CEF for electrons. Even when underestimated, the antimycin A-sensitive component of ETR1 was 15–18 μmol electrons m-2 s-1 at the three low irradiances, peaking at 45 μmol electrons m-2 s-1 at 864 μmol photons m-2 s-1 (Figure 7), where it is similar to the light-saturated LEFO2.


Partially dissecting the steady-state electron fluxes in Photosystem I in wild-type and pgr5 and ndh mutants of Arabidopsis.

Kou J, Takahashi S, Fan DY, Badger MR, Chow WS - Front Plant Sci (2015)

The difference between ΔFlux in the absence of antimycin (-AA) and the presence of antimycin A (+AA), representing an underestimate of the component of CEF inhibitable by antimycin A, is plotted against irradiance. The data are derived from Figures 1A and 2A for the wild type and from Figures 5A and 6A for the ndh mutant.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4584955&req=5

Figure 7: The difference between ΔFlux in the absence of antimycin (-AA) and the presence of antimycin A (+AA), representing an underestimate of the component of CEF inhibitable by antimycin A, is plotted against irradiance. The data are derived from Figures 1A and 2A for the wild type and from Figures 5A and 6A for the ndh mutant.
Mentions: It may be instructive to estimate the magnitude of the antimycin A-sensitive component of ETR1. In the case of the wild type, the presence of antimycin A (+AA) gave a residual ΔFlux+AA that is in general contributed by charge recombination, pseudo-cyclic electron flow and, possibly, the NDH-dependent cyclic flux (Figure 2A). Subtracting ΔFlux+AA (Figure 2A) from ΔFlux-AA (Figure 1A) gives an estimate of the antimycin A-sensitive component of ETR1. However, (ΔFlux+AA - ΔFlux-AA) is an underestimate, since in the absence of antimycin A, the contributions from charge recombination and pseudo-cyclic electron flow could well have been smaller because of competition from CEF for electrons. Even when underestimated, the antimycin A-sensitive component of ETR1 was 15–18 μmol electrons m-2 s-1 at the three low irradiances, peaking at 45 μmol electrons m-2 s-1 at 864 μmol photons m-2 s-1 (Figure 7), where it is similar to the light-saturated LEFO2.

Bottom Line: We obtained the linear electron flux (LEFO2) through both photosystems and the total electron flux through PS I (ETR1) in Arabidopsis in CO2-enriched air.ΔFlux = ETR1 - LEFO2 is an upper estimate of CEF, which consists of two components, an antimycin A-sensitive, PGR5 (proton gradient regulation 5 protein)-dependent component and an insensitive component facilitated by a chloroplastic nicotinamide adenine dinucleotide dehydrogenase-like complex (NDH).Using wild type as well as pgr5 and ndh mutants, we observed that (1) 40% of the absorbed light was partitioned to PS I; (2) at high irradiance a substantial antimycin A-sensitive CEF occurred in the wild type and the ndh mutant; (3) at low irradiance a sizable antimycin A-sensitive CEF occurred in the wild type but not in the ndh mutant, suggesting an enhancing effect of NDH in low light; and (4) in the pgr5 mutant, and the wild type and ndh mutant treated with antimycin A, a residual ΔFlux existed at high irradiance, attributable to charge recombination and/or pseudo-cyclic electron flow.

View Article: PubMed Central - PubMed

Affiliation: College of Animal Science and Technology, Northwest A&F University Yangling, China ; Division of Plant Sciences, Research School of Biology, The Australian National University Canberra, ACT, Australia.

ABSTRACT
Cyclic electron flux (CEF) around Photosystem I (PS I) is difficult to quantify. We obtained the linear electron flux (LEFO2) through both photosystems and the total electron flux through PS I (ETR1) in Arabidopsis in CO2-enriched air. ΔFlux = ETR1 - LEFO2 is an upper estimate of CEF, which consists of two components, an antimycin A-sensitive, PGR5 (proton gradient regulation 5 protein)-dependent component and an insensitive component facilitated by a chloroplastic nicotinamide adenine dinucleotide dehydrogenase-like complex (NDH). Using wild type as well as pgr5 and ndh mutants, we observed that (1) 40% of the absorbed light was partitioned to PS I; (2) at high irradiance a substantial antimycin A-sensitive CEF occurred in the wild type and the ndh mutant; (3) at low irradiance a sizable antimycin A-sensitive CEF occurred in the wild type but not in the ndh mutant, suggesting an enhancing effect of NDH in low light; and (4) in the pgr5 mutant, and the wild type and ndh mutant treated with antimycin A, a residual ΔFlux existed at high irradiance, attributable to charge recombination and/or pseudo-cyclic electron flow. Therefore, in low-light-acclimated plants exposed to high light, ΔFlux has contributions from various paths of electron flow through PS I.

No MeSH data available.


Related in: MedlinePlus