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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.


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Response of steady-state ETR1, LEFO2, and ΔFlux (A), and Y(ND) and Y(NA) (B) in leaf disks of the ndh mutant to irradiance in the absence of antimycin A. Values are means ± SE. (n = 4 leaf disks). Other conditions are as in Figure 1.
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Figure 5: Response of steady-state ETR1, LEFO2, and ΔFlux (A), and Y(ND) and Y(NA) (B) in leaf disks of the ndh mutant to irradiance in the absence of antimycin A. Values are means ± SE. (n = 4 leaf disks). Other conditions are as in Figure 1.

Mentions: In the absence of antimycin A, the ndh mutant should still be capable of generating the CEF that is sensitive to antimycin A. As expected, ΔFlux increased steadily when the irradiance was above 203 μmol photons m-2 s-1 (Figure 5A). This component of CEF maintained electron carriers on the acceptor side of PS I in a partially oxidized state, Y(NA) being between 0.2 and 0.4 (Figure 5B).


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 ndh mutant to irradiance in the absence of antimycin A. Values are means ± SE. (n = 4 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 5: Response of steady-state ETR1, LEFO2, and ΔFlux (A), and Y(ND) and Y(NA) (B) in leaf disks of the ndh mutant to irradiance in the absence of antimycin A. Values are means ± SE. (n = 4 leaf disks). Other conditions are as in Figure 1.
Mentions: In the absence of antimycin A, the ndh mutant should still be capable of generating the CEF that is sensitive to antimycin A. As expected, ΔFlux increased steadily when the irradiance was above 203 μmol photons m-2 s-1 (Figure 5A). This component of CEF maintained electron carriers on the acceptor side of PS I in a partially oxidized state, Y(NA) being between 0.2 and 0.4 (Figure 5B).

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