Ribosomal DNA in a nuclear satellite of tomato

A satellite DNA of buoyant density 1.704 constitutes approximately 5%–6% of nuclear DNA isolated from cherry tomato leaves. Isolated satellite DNA exhibits a multi-component melting profile. Kinetic complexity measurements indicate that 37% of the satellite consists of repeating units of 10 ⁵ daltons, and 48% of it consists of repeating units of 5.5 x 10⁶ daltons. The latter component is identified as DNA coding for ribosomal RNA on the basis of its buoyant density, kinetic complexity, and abundance in nuclear DNA, 3.2% as determined by saturation hybridization measurements. Saturation studies show that the more rapidly reassociating component of the satellite does not code for 5S RNA. The question of genetic linkage between satellite components is not resolved by this study.