Buoyant density studies of chloroplast and nuclear deoxyribonucleic acid from control and 3-amino-1,2,4-triazole-treated wheat seedlings, Triticum vulgare.

The isolation of chloroplast and nuclear DNA from dark- and light-grown, control- and 3-amino-1,2,4-triazole-treated wheat seedlings, Triticum vulgare, is described. Contrary to a previous report, we found that chloroplast and nuclear DNA had similar buoyant densities (1.702 grams per cubic centimeter) and that they could not be resolved by buoyant density centrifugation in CsCl. Difference in renaturation behavior of the chloroplast and nuclear DNA was used as the criterion for distinguishing one from the other. Only chloroplast DNA readily renatured whereas nuclear DNA renatured only slightly. Light-grown, 3-amino-1,2,4-triazole-treated plants were found to lack detectable quantities of chloroplast DNA whereas treated, dark-grown plants contained plastid DNA. We suggest that 3-amino-1,2,4-triazole affects the accumulation of chloroplast DNA by inhibiting the formation of chloroplast membranes, enzymes, and pigments.