Expression of GRAS genes during adventitious root formation in Pinus radiata . A) qRT-PCR was performed using RNAs from rooting-competent hypocotyls (H21) and non-competent hypocotyls (H90) from 21- and 90-day-old seedlings, respectively. B) qRT-PCR was performed using RNAs from non-competent epicotyls (E90) from 90-day-old seedlings. RNA was extracted from the base of hypocotyl (H) or epicotyl (E) cuttings treated with 10 μM indole-3-butyric acid at the indicated times. Hypocotyl or epicotyl cuttings maintained in water were used as controls. A total of 1 μg RNA was reverse transcribed, and 12.5 ng of cDNA was amplified with 400 nM of specific primers. Pine Ri18S was used as the control. Results are expressed as mean values of relative expression to time 0 ± SE from at least three biological replicates. Expression levels of PrSCL1 and PrSHR had already been measured in competent hypocotyls from 21-day-old seedlings during adventitious rooting ,. Expression of PrSCL16 was not detected in any of the RNA samples tested. SCL, SCARECROW-LIKE; SHR, SHORT-ROOT.