Studies on soluble RNA binding indoleacetic acid in etiolated mung bean hypocotyl sections

Nucleic acid was extracted by the SLS-phenol method from Phaseolus aureus hypocotyl treated with IAA-2-14C. Radioactivity in the nucleic acid fraction was found at the positions of sRNA and rRNA on an MAK column. IAA-14C was released from the radioactive compound(s) in the sRNA fraction, by alkaline hydrolysis, but not by ethanol extraction, or by dialysis to 2 M NaCl, 8 M urea, and 0.1 M EDTA. When the radioactive compound at the position of sRNA on an MAK column was further re-chromatographed on a DEAE-cellulose column and on a BD-cellulose column, it was always localized only in a settled part of the fraction of each column. From this fraction IAA-14C was released by alkaline hydrolysis. Also, IAA-14C was released from the radioactive compound in sRNA fraction, by RNase digestion, but not by pronase treatment. Results of these experiments suggest the existence of some kinds of sRNA binding IAA. The genesis of this sRNA binding IAA-14C was observed within 30 min after the supply of IAA-14C, and the sRNA became saturated with IAA-14C about 2 hr after the beginning of incubation. The behavior of sRNA binding IAA, represented by sRNA binding IAA-14C, may have a role in IAA induced growth of mung bean hypocotyl sections.