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Temperature-dependent changes in respiration rates and redox poise of the ubiquinone pool in protoplasts and isolated mitochondria of potato leaves
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2007 (Engelska)Ingår i: Physiologia Plantarum, Vol. 129, s. 175-184Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

In many environments, leaves experience large diurnal variations in temperature. Such short-term changes in temperature are likely to have important implications for respiratory metabolism in leaves. Here, we used intact leaf, protoplasts and isolated mitochondria to determine the impact of short-term changes in temperature on respiration rates (R), adenylate concentrations and the redox poise of the ubiquinone (UQ) pool in mitochondria of potato leaves. The Q10 (i.e. proportional change in R for each 10°C rise in temperature) of respiration was 1.8, both for intact leaves and protoplasts. In protoplasts, the redox poise of the extracted UQ pool (UQR/UQT) increased from 0.33 at 22°C, to 0.76 at 15°C. Further decreases in temperature (from 15 to 5°C) resulted in UQR/UQT decreasing to 0.40. Adenylate ratios in protoplasts were also temperature dependent. At high adenosine 5'-triphosphate (ATP) adenosine 5'-diphosphate (ADP) ratios (i.e. low ADP concentrations), UQR/UQT values were low, suggesting that adenylates restricted flux via the UQ-reducing pathways more than they restricted flux via pathways that oxidized UQH2. To assess whether high rates of alternative oxidase (AOX) activity could have uncoupled respiratory flux (and thus UQR/UQT) from adenylate restriction of the cytochrome (Cyt) pathway, we constructed kinetic curves of O2 uptake (via the two pathways) vs UQR/UQT in isolated mitochondria, measured at two temperatures (15 and 25°C); measurements were made for mitochondria operating under state 3 (i.e. +ADP) and state 4 (i.e. −ADP) conditions. In contrast to the Cyt pathway, flux via the AOX was temperature insensitive, with maximal rates of AOX activity representing 21–57% of total O2 uptake in isolated mitochondria. We conclude that temperature-dependent variations in UQR/UQT are largely dependent on temperature-dependent changes in adenylate ratios, and that flux via the AOX could in some circumstances help reduce maximal UQ values.

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2007. Vol. 129, s. 175-184
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URN: urn:nbn:se:umu:diva-15940DOI: doi:10.1111/j.1399-3054.2006.00823.xOAI: oai:DiVA.org:umu-15940DiVA, id: diva2:155612
Tillgänglig från: 2007-08-06 Skapad: 2007-08-06 Senast uppdaterad: 2018-06-09Bibliografiskt granskad

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Gardeström, Per

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