Differences in Leucyl-Transfer RNA's and Synthetase in Soybean Seedlings

Charged leucyl-transfer RNA (leucyl-tRNA) of soybean cotyledons can be fractionated into six radioactive peaks on a Freon column. Four leucyl-tRNA peaks are observed with the homologous hypocotyl system. Hypocotyl synthetase preparations only slightly acylate the other two leucyl-tRNA's (species 5 and 6). Further, leucyl-tRNA5 and 6 of the hypocotyl are present in small amounts in comparison to the cotyledon. Therefore, the rate-limiting quantities of synthetase and tRNA5 and 6 obtained from the hypocotyl prevent the detection of these two species of tRNA when a homologous hypocotyl system is used. To measure the relative amounts of hypocotyl tRNA's, the cotyledon synthetase preparation is employed. Preliminary results show that 6-benzyladenine increases the acylation of leucyl-tRNA5 and 6 and decreases acylation of tRNA1 in the hypocotyl. Synthetase preparations from cytokinin-treated plants are not significantly affected.