Early auxin-regulated polyadenylylated mRNA sequences in pea stem tissue

Polyadenylylated mRNA from etiolated pea stem segments treated with or without 20 muM indoleacetic acid (IAA) for various periods of time was assayed by translating it in a wheat germ extract containing [(35)S]methionine and separating the translation products by two-dimensional gel electrophoresis. Within 2 hr IAA causes at least five mRNA sequences to increase in translational activity, relative to initial levels and to simultaneous controls; three of these rise significantly within 20 min after exposure of tissue to IAA but are apparently not elevated at 10 min, whereas the others begin to increase at successive times later than 30 min, and still others begin to change only later than 2 hr. These observations indicate an early, highly selective IAA regulation of mRNA amounts or activities, becoming progressively more extensive with time. The earliest detected enhancement seems close to the primary action of IAA but appears not to be rapid enough to be responsible for auxin induction of cell enlargement.