Poster: Hormone synthesis & metabolism

Abs # 482: Increased size of floral organs results from expression of AP3::ipt in transgenic petunia

Presenter:	Shibuya, Kenichi , kshibuya@mail.ifas.ufl.edu
Authors	Shibuya, Kenichi  (A)   Loucas, Holly M. (A)   Ciardi, Joseph A. (B)   Clark, David G. (A)
Affiliations:	(A): Environmental Horticulture, University of Florida (B): Plantgenix, Inc.
Web Site:	http://hort.ifas.ufl.edu/floriculture/floriculture_bio.htm

Cytokinin is a plant hormone that is involved in many physiological processes, including cell division. The ipt gene from the Ti plasmid of Agrobacterium tumefaciens encodes isopentenyl transferase, a key enzyme in cytokinin biosynthesis. We expressed the ipt gene in petunia (Petunia x hybrida) under the control of the APETALA3 (AP3) promoter from Arabidopsis. AP3 is a B-function floral organ identity gene involved in petal and stamen development. In the resulting transgenic plants, corolla diameter was increased up to 1.2X and the fresh weight of whole flowers and ovaries was increased up to 2X and 4.5X, respectively, compared to controls. In addition mature seed weight was also increased up to 1.2X of control in AP3::ipt plants. No morphological change in vegetative tissues was observed in AP3::ipt plants compared to wild type. Previous reports have shown that expression of the ipt gene driven by a fruit specific promoter leads to changes in fruit ripening, and that expression of this gene driven by a senescence associated promoter (SAG) leads to a delay in leaf and flower senescence. Here we utilize a strategy to produce bigger flowers, fruits, and seeds by heterologous expression of the A. tumefaciens ipt gene under the control of an Arabidopsis AP3 promoter. This strategy has potential for use in producing ornamental crops with large flowers and crop species such as corn, rice, and tomato with increased yield.