A Comparison of Respiratory Pathways in Fully Habituated and Normal Non-organogenic Sugarbeet Callus

The respiration of cells and isolated mitochondria of a habituated non-organogenic (HNO) cell line (auxin- and cytokinin-independent) and of a normal (N) cell line (auxin- and cytokinin-requiring) from sugarbeet (Beta vulgaris L.) was investigated. Oxygen uptake by both cells and mitochondria of the HNO line was higher than that of the N line. Respiration in the presence of cyanide (i.e. capacity of the alternative pathway) was also higher in the HNO callus as compared with the N one. The measurements of O2 uptake from isolated HNO and N mitochondria showed that addition of a mixture of substrates (NADH, succinate, malate and NAD) resulted in a higher respiration via the CN-resistant pathway in mitochondria from HNO cells. The activity of cytochrome c oxidase was twice as high as in the N cells as compared with the HNO cells. Immunoblots also showed that a higher alternative oxidase protein was present in HNO cells than in the N cells. A model showing the relationships between the different metabolic pathways previously studied in the HNO cells and the higher respiration via the CN-resistant pathway in the HNO cells is proposed.