Satellite-rich DNA in cucumber: hormonal enhancement of synthesis and subcellular identification

Abstract

Cucumber hypocotyl DNA in neutral CsCl distributes into a mainband comprising 59% of the total, and two large satellite bands which contribute 41% to the DNA pattern. Organelle enrichment studies show that the densities of mitochondrial and chloroplast DNA coincide with those of the satellite bands. At least 12-19% of total cucumber DNA is associated with the cytoplasmic organelles. These values, which are several times larger than those usually quoted for higher plants, are correlated with an unusually low amount of DNA per haploid nucleus in cucumber. Synthesis of the satellite DNAs, as well as mainband DNA, is appreciably stimulated in vivo by application of the plant hormone, gibberellin. Endogenous and hormone-enhanced synthesis of the satellite DNAs is proportionately greater in target tissue showing a high rate of organelle synthetic activity.