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The Ca2+-Regulation of the Mitochondrial External NADPH Dehydrogenase in Plants Is Controlled by Cytosolic pH.

Hao MS, Jensen AM, Boquist AS, Liu YJ, Rasmusson AG - PLoS ONE (2015)

Bottom Line: NADPH oxidation responded to changes in Ca2+ concentrations more rapidly than NADH oxidation did.Thus, cytosolic acidification is an important activator of external NADPH oxidation, by decreasing the Ca2+-requirements for NDB1.The results are discussed in relation to the present knowledge on how whole cell NADPH redox homeostasis is affected in plants modified for the NDB1 gene.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Lund University, Lund, Sweden.

ABSTRACT
NADPH is a key reductant carrier that maintains internal redox and antioxidant status, and that links biosynthetic, catabolic and signalling pathways. Plants have a mitochondrial external NADPH oxidation pathway, which depends on Ca2+ and pH in vitro, but concentrations of Ca2+ needed are not known. We have determined the K0.5(Ca2+) of the external NADPH dehydrogenase from Solanum tuberosum mitochondria and membranes of E. coli expressing Arabidopsis thaliana NDB1 over the physiological pH range using O2 and decylubiquinone as electron acceptors. The K0.5(Ca2+) of NADPH oxidation was generally higher than for NADH oxidation, and unlike the latter, it depended on pH. At pH 7.5, K0.5(Ca2+) for NADPH oxidation was high (≈100 μM), yet 20-fold lower K0.5(Ca2+) values were determined at pH 6.8. Lower K0.5(Ca2+) values were observed with decylubiquinone than with O2 as terminal electron acceptor. NADPH oxidation responded to changes in Ca2+ concentrations more rapidly than NADH oxidation did. Thus, cytosolic acidification is an important activator of external NADPH oxidation, by decreasing the Ca2+-requirements for NDB1. The results are discussed in relation to the present knowledge on how whole cell NADPH redox homeostasis is affected in plants modified for the NDB1 gene.

No MeSH data available.


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Ca2+ dependence of NAD(P)H oxidation in mitochondria at different pH values.(A) NADH and (B) NADPH oxidation activity of potato tuber mitochondria were measured at pH 6.0–7.5 as O2 consumption, using 1 mM NAD(P)H as substrate. (C) NADPH oxidation with DcQ as final electron acceptor in mitochondria from N. sylvestris expressing StNDB1 was measured at pH 6.0–7.5. Closed and open symbols denote presence and absence of 1 mM free Ca2+, respectively. In (C), wildtype (WT) N. sylvestris, the overexpression lines S17 and S6, and the suppression line S8 are denoted as circles, triangles, squares and inverted triangles, respectively. Data displays average for 2–3 independent mitochondrial preparations, with error bars denoting SD in (A) and (B) and SE in (C).
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pone.0139224.g001: Ca2+ dependence of NAD(P)H oxidation in mitochondria at different pH values.(A) NADH and (B) NADPH oxidation activity of potato tuber mitochondria were measured at pH 6.0–7.5 as O2 consumption, using 1 mM NAD(P)H as substrate. (C) NADPH oxidation with DcQ as final electron acceptor in mitochondria from N. sylvestris expressing StNDB1 was measured at pH 6.0–7.5. Closed and open symbols denote presence and absence of 1 mM free Ca2+, respectively. In (C), wildtype (WT) N. sylvestris, the overexpression lines S17 and S6, and the suppression line S8 are denoted as circles, triangles, squares and inverted triangles, respectively. Data displays average for 2–3 independent mitochondrial preparations, with error bars denoting SD in (A) and (B) and SE in (C).

Mentions: External NAD(P)H oxidation is Ca2+-dependent in the neutral pH range but not at low pH in spinach and H. tuberosus mitochondria [30,39]. In potato (Fig 1A), the NADH oxidation activity was 5–8 fold higher in the presence of Ca2+ than in its absence at pH 6.8 and pH 7.5, whereas the activity at pH 6 was Ca2+-independent. In a similar way, NADPH oxidation strongly depended on the presence of Ca2+ at pH 6.8 and 7.5, but not at pH 6.0 (Fig 1B). However, unlike NADH oxidation, NADPH oxidation decreased drastically from pH 6.8 to pH 7.5.


The Ca2+-Regulation of the Mitochondrial External NADPH Dehydrogenase in Plants Is Controlled by Cytosolic pH.

Hao MS, Jensen AM, Boquist AS, Liu YJ, Rasmusson AG - PLoS ONE (2015)

Ca2+ dependence of NAD(P)H oxidation in mitochondria at different pH values.(A) NADH and (B) NADPH oxidation activity of potato tuber mitochondria were measured at pH 6.0–7.5 as O2 consumption, using 1 mM NAD(P)H as substrate. (C) NADPH oxidation with DcQ as final electron acceptor in mitochondria from N. sylvestris expressing StNDB1 was measured at pH 6.0–7.5. Closed and open symbols denote presence and absence of 1 mM free Ca2+, respectively. In (C), wildtype (WT) N. sylvestris, the overexpression lines S17 and S6, and the suppression line S8 are denoted as circles, triangles, squares and inverted triangles, respectively. Data displays average for 2–3 independent mitochondrial preparations, with error bars denoting SD in (A) and (B) and SE in (C).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4587368&req=5

pone.0139224.g001: Ca2+ dependence of NAD(P)H oxidation in mitochondria at different pH values.(A) NADH and (B) NADPH oxidation activity of potato tuber mitochondria were measured at pH 6.0–7.5 as O2 consumption, using 1 mM NAD(P)H as substrate. (C) NADPH oxidation with DcQ as final electron acceptor in mitochondria from N. sylvestris expressing StNDB1 was measured at pH 6.0–7.5. Closed and open symbols denote presence and absence of 1 mM free Ca2+, respectively. In (C), wildtype (WT) N. sylvestris, the overexpression lines S17 and S6, and the suppression line S8 are denoted as circles, triangles, squares and inverted triangles, respectively. Data displays average for 2–3 independent mitochondrial preparations, with error bars denoting SD in (A) and (B) and SE in (C).
Mentions: External NAD(P)H oxidation is Ca2+-dependent in the neutral pH range but not at low pH in spinach and H. tuberosus mitochondria [30,39]. In potato (Fig 1A), the NADH oxidation activity was 5–8 fold higher in the presence of Ca2+ than in its absence at pH 6.8 and pH 7.5, whereas the activity at pH 6 was Ca2+-independent. In a similar way, NADPH oxidation strongly depended on the presence of Ca2+ at pH 6.8 and 7.5, but not at pH 6.0 (Fig 1B). However, unlike NADH oxidation, NADPH oxidation decreased drastically from pH 6.8 to pH 7.5.

Bottom Line: NADPH oxidation responded to changes in Ca2+ concentrations more rapidly than NADH oxidation did.Thus, cytosolic acidification is an important activator of external NADPH oxidation, by decreasing the Ca2+-requirements for NDB1.The results are discussed in relation to the present knowledge on how whole cell NADPH redox homeostasis is affected in plants modified for the NDB1 gene.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Lund University, Lund, Sweden.

ABSTRACT
NADPH is a key reductant carrier that maintains internal redox and antioxidant status, and that links biosynthetic, catabolic and signalling pathways. Plants have a mitochondrial external NADPH oxidation pathway, which depends on Ca2+ and pH in vitro, but concentrations of Ca2+ needed are not known. We have determined the K0.5(Ca2+) of the external NADPH dehydrogenase from Solanum tuberosum mitochondria and membranes of E. coli expressing Arabidopsis thaliana NDB1 over the physiological pH range using O2 and decylubiquinone as electron acceptors. The K0.5(Ca2+) of NADPH oxidation was generally higher than for NADH oxidation, and unlike the latter, it depended on pH. At pH 7.5, K0.5(Ca2+) for NADPH oxidation was high (≈100 μM), yet 20-fold lower K0.5(Ca2+) values were determined at pH 6.8. Lower K0.5(Ca2+) values were observed with decylubiquinone than with O2 as terminal electron acceptor. NADPH oxidation responded to changes in Ca2+ concentrations more rapidly than NADH oxidation did. Thus, cytosolic acidification is an important activator of external NADPH oxidation, by decreasing the Ca2+-requirements for NDB1. The results are discussed in relation to the present knowledge on how whole cell NADPH redox homeostasis is affected in plants modified for the NDB1 gene.

No MeSH data available.


Related in: MedlinePlus