Expression of gene specific to ethylene-induced ripeness to flower in Dutch iris bulbs

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Using Poly-T primers, cDNAs were transcripted from RNAs extracted from the shoot tip of Dutch iris 'Blue Magic' bulbs, and they were amplified through PCR. Gene expression was analyzed by deferential display method, electrophoresing these PCR products on agarose gel. A PCR product (namely CG-01) was detected specifically in shoot tip of small-size bulbs (9g) without ethylene application, which were considered to be in juvenile phase and insensitive to inductive chilling. Investigation was focusted on this gene fragment.Before exposing bulbs to high temperature in 1999, expression of CG-01 was detected strongly in small-size bulbs and slightly in large-size bulbs (17g). However, the expression of CG-01 disappeared after exposing them to 100ppm ethylene for 24 hr. The flowering percentage of small-size and large-size bulbs after chilling treatment were 0% and 33%, respectively, if ethylene was not applied, indicating that all or most of bulbs were at juvenile phase. DNA sequence of CG-01 toward the 3' terminal was analyzed by a 3'RACE method suing bulbs after exposing them to high temperature. A PCR product which was amplified by the adaptor primer and a synthetic primer adupted to CG-01 sequence was obtained. However, sequence of this PCR product and that of CG-01 already known was not homologous. These results indicated that expression of CG-01 disappeared after summer even in small size bulbs at juvenile phase.