Polyadenylated RNA sequences which are reduced in concentration following auxin treatment of soybean hypocotyls.

Previous work has shown that any effect of exogenous auxin on gene expression in soybean hypocotyl tissue must be restricted to a relatively small fraction of the polyadenylated RNA. However, kinetic hybridization analysis with cDNA probes revealed that a minor abundant class of sequences is markedly reduced in concentrations in the auxin-treated polyadenylated RNA. Recombinant plasmids containing copies of polyadenylated RNA species were constructed using the G-C tailing procedure and clones of auxin-regulated sequences were detected by differential in situ hybridization with cDNA of polyadenylated RNA from auxin-treated or untreated hypocotyls. Although the 12 clones which were selected all contained different size inserts, and were therefore independent, 11 of these apparently hybridized to just two different RNA species. The rate constant of the auxin-sensitive abundant component of the untreated polyadenylated RNA/DNA hybridization was similar to that of the reaction between the two major groups of clones and untreated polyadenylated RNA. This indicates that these cloned sequences are homologous with that cDNA fraction. The twelfth clone is thought to be representative of a group of less abundnt auxin-regulated polyadenylated mRNA species which had been detected in an earlier analysis of the in vitro translation products of soybean hypocotyl RNA. Both the timing and the extent of the influence of auxin on the relative concentration of these cloned sequences are quite consistent with a close relationship between growth regulation by auxin and its effects on gene expression.