Do mitochondria from hybrid wheat use energy more efficiently than those from its parents?

Details

This comparative laboratory study examined mitochondria from the wheat hybrid 31MS × 28, mitochondria from its parents, and mixtures of parental mitochondria. In polarographic assays, hybrid mitochondria exceeded parental mitochondria in both ADP:O ratios and respiratory control when using alpha-ketoglutarate, malate, and succinate. The hybrid mitochondria’s ADP:O ratios were 5.8 ± 0.2 for alpha-ketoglutarate, 3.8 ± 0.15 for malate, and 3.4 ± 0.2 for succinate. High P:O ratios were also observed in manometric assays.

Mixtures of parental mitochondria exceeded the averages of the parents, showing complementation and approaching the activities of hybrid mitochondria. Complementation was observed only with NAD-linked substrates.

Dinitrophenol uncoupled all mitochondria, but the uncoupling was smallest in hybrid mitochondria. Hybrid mitochondria had the greatest ATPase activity. Mixtures of parental mitochondria also showed complementation in ATPase activity. ATPase activity was stimulated least in hybrid mitochondria and in parental mixtures; the abstract does not specify the stimulus in this statement.

The authors discussed the high phosphorylation ratios as direct evidence that heterosis is characterized by high efficiency. They also suggested that, because of their consistent repeatability and specificity to hybrids, P:O ratios measured in rapidly isolated hybrid mitochondria may provide revealing information about supramaximal efficiency of oxidative phosphorylation.