Present address: Department of Chemistry, Leeds University, Leeds, UK.
Temperature-dependent changes in respiration rates and redox poise of the ubiquinone pool in protoplasts and isolated mitochondria of potato leaves
Article first published online: 22 NOV 2006
Volume 129, Issue 1, pages 175–184, January 2007
How to Cite
Covey-Crump, E. M., Bykova, N. V., Affourtit, C., Hoefnagel, M. H. N., Gardeström, P. and Atkin, O. K. (2007), Temperature-dependent changes in respiration rates and redox poise of the ubiquinone pool in protoplasts and isolated mitochondria of potato leaves. Physiologia Plantarum, 129: 175–184. doi: 10.1111/j.1399-3054.2006.00823.x
- Issue published online: 22 NOV 2006
- Article first published online: 22 NOV 2006
- Received 30 June 2006; revised 25 July 2006
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.