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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

Response of steady-state ETR1, LEFO2 and ΔFlux (A), and Y(ND) and Y(NA) (B) in leaf disks of the pgr5 mutant to irradiance in the absence of antimycin A. Values are means ± SE. (n = 16 leaf disks). Other conditions are as in Figure 1.
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Figure 3: Response of steady-state ETR1, LEFO2 and ΔFlux (A), and Y(ND) and Y(NA) (B) in leaf disks of the pgr5 mutant to irradiance in the absence of antimycin A. Values are means ± SE. (n = 16 leaf disks). Other conditions are as in Figure 1.

Mentions: In the absence of antimycin A, the pgr5 mutant showed a ΔFlux that only increased slowly with increase in irradiance (Figure 3A). For example, ΔFlux was only 4.7 μmol electrons m-2 s-1 at the irradiance 559 μmol photons m-2 s-1. This seems surprising, given that the acceptor side was highly reduced, Y(NA) being 0.73 (Figure 3B), which should have favored charge recombination and pseudo-cyclic electron flow. Probably, however, charge recombination could not occur because P700 was almost completely reduced and there was hardly any P700+ available for charge recombination. That is, the near-zero Y(ND) may be the reason for the very small ΔFlux at 559 above 559 μmol photons m-2 s-1. Further, this small ΔFlux, with a magnitude that was about 10% of LEFO2, also implies that pseudo-cyclic electron transfer was not very active at this irradiance despite the highly reduced state of the acceptor side.


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)

Response of steady-state ETR1, LEFO2 and ΔFlux (A), and Y(ND) and Y(NA) (B) in leaf disks of the pgr5 mutant to irradiance in the absence of antimycin A. Values are means ± SE. (n = 16 leaf disks). Other conditions are as in Figure 1.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 3: Response of steady-state ETR1, LEFO2 and ΔFlux (A), and Y(ND) and Y(NA) (B) in leaf disks of the pgr5 mutant to irradiance in the absence of antimycin A. Values are means ± SE. (n = 16 leaf disks). Other conditions are as in Figure 1.
Mentions: In the absence of antimycin A, the pgr5 mutant showed a ΔFlux that only increased slowly with increase in irradiance (Figure 3A). For example, ΔFlux was only 4.7 μmol electrons m-2 s-1 at the irradiance 559 μmol photons m-2 s-1. This seems surprising, given that the acceptor side was highly reduced, Y(NA) being 0.73 (Figure 3B), which should have favored charge recombination and pseudo-cyclic electron flow. Probably, however, charge recombination could not occur because P700 was almost completely reduced and there was hardly any P700+ available for charge recombination. That is, the near-zero Y(ND) may be the reason for the very small ΔFlux at 559 above 559 μmol photons m-2 s-1. Further, this small ΔFlux, with a magnitude that was about 10% of LEFO2, also implies that pseudo-cyclic electron transfer was not very active at this irradiance despite the highly reduced state of the acceptor side.

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