Invasive Species Compendium

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Abstract

Satellite DNA specific to knob heterochromatin in Cucumis metuliferus (Cucurbitaceae).

Abstract

Buoyant density gradient analysis of nuclear DNA of 4 Cucumis species showed asymmetric profiles indicating the presence of satellite DNA sequences in the nuclear genome. A highly repeated satellite DNA sequence was isolated from the nuclear genome of C. metuliferus under neutral CsCl gradients. The satellite DNA constituted about 4.96% of total nuclear DNA and had a G + C content of 48.06%. The kinetic complexity of satellite DNA was 150 times smaller the T4 phage DNA and the base sequence divergence was low. 3H-labelled cRNA transcribed from satellite DNA hybridized to 6 heterochromatic knobs of pachytene chromosomes. Knob heterochromatin was distinguished by Giemsa C-banding of pachytene chromosomes. Restriction enzyme analysis and Southern blot hybridization indicated that the satellite DNA was tandemly arranged and predominantly formed 2 bands of 210 and 151 bp. Absence of knob satellite DNA of C. metuliferus in the nuclear genomes of C. melo, C. anguria and C. sativus showed that C. metuliferus is isolated within the genus Cucumis.