Newly Synthesized mRNA Is Translated during the Initial Imbibition Phase of Germinating Maize Embryo

Abstract

An attempt was made to detect the time of appearance of the newly synthesized mRNA in the polysomes of germinating maize axes. Free polysomes were prepared from embryonic axes rehydrated for 2 h in the presence of radioactively labeled uridine. These polysomes were labeled and to contain labeled particles sedimenting, after dissociation with EDTA, in the 10S to 40S region of a sucrose gradient. The labeled polysomal RNA migrates heterogeneously in a gel with a mean size corresponding to about 16S, and 60% of these molecules are polyadenylated. Apparently the newly synthesized RNA associated with the polysomes after 2 h of germination consists of messenger RNA molecules. Analysis of the polysomes prepared 0.5 and 1 h after the start of imbibition suggests that translation of the newly synthesized mRNA probably occurs within the 1st h imbibition of the isolated axis, well before the completion of the initial water uptake.