Characterization of the genome of the cellular slime mold Dictyostelium discoideum

The cellular DNA's of Dictyostelium discoideum have been characterized by their behavior in CsCl buoyant density-gradient centrifugation and by their renaturation kinetics and the complexity of the nuclear DNA is but 11 times that of Escherichia coli.

Abstract

The cellular DNA's of Dictyostelium discoideum have been characterized by their behavior in CsCl buoyant density-gradient centrifugation and by their renaturation kinetics. Whole-cell DNA exhibited three bands on CsCl density-gradient centrifugation. Two of these, p = 1.676 g/cm3 (main band) and 1.687 (satellite) are nuclear. The third, of p = 1.682 is mitochondrial and represents approximately 28% of whole-cell DNA. Appropriate hybridization experiments with cytoplasmic rRNA show that rRNA cistrons constitute 2.2% of nuclear DNA. This portion of the nuclear DNA possesses a ρ of approximately 1.682 and bands in the mitochondrial DNA region. Non-reiterated sequences make up approximately 70% of the Dictyostelium genome (criterion of Tm − 23 deg. C) and are characterized by a C0t12 (pure) of 70. Reiterated sequences make up 30% of the genome and are characterized by a C0t12 (pure) of 0.28. The complexity of the nuclear DNA of Dictyostelium is but 11 times that of Escherichia coli (approximately 30 ×109 daltons). The mitochondrial DNA of Dictyostelium exhibits a C0t12 of 0.15 and a calculated complexity of 35 to 40 × 106 daltons.