Disappearance of stored polyadenylic acid and mRNA during early germination of radish (Raphanus sativus L.) embryo axes.

Polyadenylic acid [poly (A)] is detected, characterized and quantitated in dry radish embryo axis RNA using a (3)H poly (U) probe. The amount of poly (A) gradually decreases after the onset of soaking, and, after a few hours, recovers to the initial level. This variation is shown to result from the addition of two opposed phenomena: the decay of stored poly (A) and the accumulation of newly synthesized poly (A). Stored poly (A), as well as the "in vivo" protein synthesis coded for by preformed mRNA, decreases during early germination with a half-life of two hours. As a whole, these results demonstrate that at least a fraction of the stored mRNA is translated as soon as the seed is soaked and that its role is rapidly taken over by newly-made mRNA.