ENHANCEMENT OF INFECTIVITY BY COMBINATION OF TWO RIBONUCLEIC ACID COMPONENTS FROM ALFALFA MOSAIC VIRUS

RNA was extracted from alfalfa mosaic virus 425. Infectivity was determined in density gradient fractions and in all possible combinations of 2 fractions. Certain combinations were remarkably infectious. This led to the purification through 2 cycles of sucrose gradient centrifugation of a 27 S and a 14 S RNA, from bottom component and top component a, respectively. The purified bottom component RNA had a low infectivity;. when purified top component a RNA was added, infectivity increased considerably. Possible explanations for this effect are discussed.