Temperature-dependent changes in respiration rates and redox poise of the ubiquinone pool in protoplasts and isolated mitochondria of potato leaves
In: Plant respiration, Jg. 129 (2007), Heft 1, S. 175-184
Online
academicJournal
- print, 1 p.3/4
Zugriff:
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 at22°C, to 0.76at15°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 02 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.
Titel: |
Temperature-dependent changes in respiration rates and redox poise of the ubiquinone pool in protoplasts and isolated mitochondria of potato leaves
|
---|---|
Autor/in / Beteiligte Person: | COVEY CRUMP, Elizabeth M ; BYKOVA, Natalia V ; AFFOURTIT, Charles ; HOEFNAGEL, Marcel H. N ; GARDESTRÖM, Per ; ATKIN, Owen K |
Link: | |
Zeitschrift: | Plant respiration, Jg. 129 (2007), Heft 1, S. 175-184 |
Veröffentlichung: | Oxford: Blackwell, 2007 |
Medientyp: | academicJournal |
Umfang: | print, 1 p.3/4 |
ISSN: | 0031-9317 (print) |
Schlagwort: |
|
Sonstiges: |
|