The structure of cauliflower mosaic virus genome

Native cauliflower mosaic virus (CaMV) DNA sedimented as two major components, a nicked circular form (19.0 S) and a linear form (17.1 S). Upon electrophoresis in 2.5% polyacrylamide gels the nicked circular form migrated more slowly than the linear form. The nicked circular form was infectious; the linear form had little infectivity. Upon denaturation using heat and formaldehyde or alkali treatment for a short time, CaMV DNA sedimented as two components (16.1 S and 13.5 S) in sucrose density gradients. These were considered to be the single-stranded circular and linear forms respectively. After prolonged alkali treatment some of the CaMV DNA broke down into fragments with an average size of one-quarter to one-fifth of the normal single-stranded length. The nature of the alkali-labile regions was investigated and ribonucleosides, comprising less than 1% of the total nucleic acid, were identified. The significance of these findings is discussed.