Modification in transfer RNA during the differentiation of wheat seedlings.

Abstract

The purpose of this study was to determine whether or not detectable changes could be observed in the distribution of the various aminoacyl-tRNA''s during morphogenesis. The data (based on MAK chromatography) presented show that there are quantitative changes between the species of given aminoacyl-tRNA''s. The changes, demonstrated by increases or decreases in certain peaks eluted from MAK, may be accounted for in 2 ways. There could occur during differentiation an increase in the quantity of 1 degenerate species of lysyl-tRNA. Alternatively, a quantitative change could result from the formation of a completely new degenerate species of lysyl-tRNA, but a species which coelutes with one extant in both embryo and seedling. Neither alternative can be favored at this time. In either case, differences in tRNA''s which can be resolved by MAK chromatography do not necessarily represent anticodon changes. Changes in tRNA molecules which are not associated with changes in the anticodon region result in altered chromatographic profiles. Whatever produces the alterations observed, they occur when the seedling is undergoing rapid differentiation. In view of the role of tRNA''s in the translation process, changes in the constitution of tRNA molecules may be necessary for the events of differentiation. Similar, transfer RNA could implement the inactivation of "old" messages begun with a common codon sequence recognized by a regulatory tRNA anticodon. The presence or absence of this unique tRNA would then determine whether or not the messengers could be read. Modulating triplets could thus temporally regulate the expression of a group of genes, serving the same role in differentiation which has been suggested for histones.