Gibberellin A3 as an epigenetic determinant of global DNA hypo-methylation in tobacco

Gibberellins (GAs) are a large family of tetracyclic diterpenoids, controlling important aspects of growth and development throughout the plant life cycle. To explore the possibility that gibberellin A 3 (GA 3 ) signalling induces epigenetic alteration(s), we carried out a field experiment study using Nicotiana tabacum as a model system. The GA 3 application on leaves resulted in increased plant-height, foliage density, leaf cell area, and trichome density. The plants exposed to GA 3 also exhibited: 1 ) increased chromatin de-condensation, 2 ) reduced global DNA methylation, 3 ) reduced DNA methyltransferases (NtDNMTs) activities accompanied by decreased amounts of NtMET1 and NtCMT3 transcripts, and 4 ) partial restoration of phenotype and expression of epigenetically silenced reporter transgene. Based on these observations, we propose that GA 3 application induces complex epigenetic re-programming, which may lead to distinct developmental phenotypes. These results could provide an important insight for future studies on epigenetic mechanism(s) in other important crops.