A comparison between mitochondrial DNA of an isogenic male-sterile (5) and male-fertile (F) couple (HA89) of sunflower.

Mitochondrial DNA from etiolated seedling of male-fertile (F) and male-sterile (S) sunflower (Helianthus annuus L.) has been investigated for the first time in an isogenic couple HA89. 1. The mt-DNAs isolated from the S and F cytoplasms give a sharp and symmetrical band at 1.706 g/ml in an analytical CsCI gradient ultracentrifugation. 2. In polyacrylamide gel it is found that mitochondria from F cytoplasm contain a Low-Molecular-Weight (LMW) mt-DNA molecule of 1.45 Kilobase-pairs (kb) in addition to the major mt-DNA. On the contrary, mitochondria from S cytoplasm contain no LMW molecule. Treatments with DNAse, RNAse and Nuclease S1 show that this LMW mt-DNA molecule consists of a supercoiled circular DNA. The length and form of the LMW molecule are confirmed by electron microscopy observations. 3. The mt-DNAs from S and F cytoplasms have also been investigated using restriction endonuclease digestions (Sa11, Xho1, Bg11). The electrophoresis of the resulting fragments reveals several differences between the S and F cytoplasm. It is not known whether the differences observed between F and S mt-DNA are correlated with the cytoplasmic male sterility phenotype.