Expression of two gibberellin-regulated cDNAs during early flower development in tomato (Solanum lycopersicon ). Effect of grafting and paclobutrazol

To study the role of translocation of gibberellin (GA) intermediates or bioactive GAs from other plant parts to buds during early flower development in tomato (Solanum lycopersicon), the effect of grafting and paclobutrazol (PAC) treatment on the expression of tgas 100 and tgas 118, two GA-regulated mRNAs, was analysed. Both mRNAs accumulated in a dose-dependent fashion. Application of 0.5 ng GA 3 per bud to developmentally arrested flower buds of a GA-deficient mutant of tomato (gib-1) induced tgas 100 expression, while the tgas 118 abundance increased. For obtaining normal flower development through anthesis in the mutant, a single GA 3 treatment was required of at least 5 ng GA, per bud. In wild-type flower buds, PAC decreased the abundance of tgas 100 and tgas 118 mRNAs either when PAC was sprayed on whole plants or directly applied to buds. When only the wild-type buds were treated with PAC, the expression profiles characteristic for untreated buds were not restored by translocation of endogenous GAs. Grafting of gib-1 scions onto wild-type donor plants did not result in normal flower development or expression profiles like in wild-type buds. We conclude that the role of GA transport in early flower development of tomato is negligible and that the GAs required for development have to be synthesized in the flower bud itself.