Heterogeneous population of mitochondrial DNA molecules in higher plants

Abstract

THE physicochemical properties of mitochondrial (mt)-DNA of higher plants have been reported1–4. mt-DNAs occur as closed circles with molecular weights of (60–70) × 106 and it is likely that each mitochondria contains several of these circles. mt-DNAs isolated from different higher plants exhibit similar physicochemical parameters: all mt-DNAs so far analysed1–5 in higher plants band at a unique buoyant density of 1.706 g cm−3 in neutral CsCl gradients and the few published melting points and reassociation kinetics are not significantly different2–4. Not enough values have been reported to state on possible differences in the contour length measured by electron microscopy. Thus, mt-DNAs isolated from different higher plants cannot be specifically identified by conventional physicochemical techniques. We have recently reported that the analysis of restriction nuclease digests by gel electrophoresis provides a very sensitive test to identify specifically chloroplastic (cp)-DNAs isolated from different plant genera and species6. We show here that this technique also allows the characterisation and the specific identification of mt-DNAs isolated from various higher plants. We used EcoRI specific cleavage to evidence the general occurrence of heterogeneous population of mt-DNA molecules within an higher plant and to detect clear differences between mt-DNAs extracted from normal and cytoplasmic male-sterile wheat.