During early flower development, AG also directly activates GA-REQUIRING4(GA4), which encodes a key gibberellin biosynthetic enzyme [21].The functional significance of this remains unknown, although onepossibility is that gibberellin could function in a positive feedbackloop to reinforce expression of organ identity genes [38]. A furtherlink between organ identity genes and hormone function is indicatedby the large number of SEP3 targets involved in signallingand homeostasis of auxin, gibberellin and brassinosteroids [25].The same authors showed that binding sequences for the auxinresponse factors (ARFs) are enriched in the vicinity of SEP3 bindingsites and that a dominant repressive version of SEP3 causesfloral defects similar to those of auxin signalling mutants, suggestingthat SEP3 and ARFs could co-operate in the regulation ofauxin-responsive genes [25].
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