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DEVELOPMENT AND HORMONE ACTION

Analysis of the DECREASED APICAL DOMINANCE Genes of Petunia in the Control of Axillary Branching^1,[C],[OA]

HortResearch, Private Bag 92169, Mt. Albert, Auckland, New Zealand (J.L.S., B.J.J., K.C.S.); Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721–0036 (C.A.N.); and School of Biological Sciences, University of Auckland, Auckland, New Zealand (K.M.P.)

Control of branch development is a major determinant of architecture in plants. Branching in petunia (Petunia hybrida) is controlled by the DECREASED APICAL DOMINANCE (DAD) genes. Gene functions were investigated by plant grafting, morphology studies, double-mutant characterization, and gene expression analysis. Both dad1-1 and dad3 increased branching mutants can be reverted to a near-wild-type phenotype by grafting to a wild-type or a dad2 mutant root stock, indicating that both genes affect the production of a graft-transmissible substance that controls branching. Expression of the DAD1 gene in the stems of grafted plants, detected by quantitative reverse transcription-polymerase chain reaction correlates with the branching phenotype of the plants. The dad2-1 mutant cannot be reverted by grafting, indicating that this gene acts predominantly in the shoot of the plant. Double-mutant analysis indicates that the DAD2 gene acts in the same pathway as the DAD1 and DAD3 genes because the dad1-1dad2-1 and dad2-1dad3 double mutants are indistinguishable from the dad2-1 mutant. However, the dad1-1dad3 double mutant has an additive phenotype, with decreased height of the plants, delayed flowering, and reduced germination rates compared to the single mutants. This result, together with the observation that the dad1-1 and dad3 mutants cannot be reverted by grafting to each other, suggests that the DAD1 and DAD3 genes act in the same pathway, but not in a simple stepwise fashion.

² Present address: Botany Department, La Trobe University, Melbourne 3086, Australia.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Kimberley C. Snowden (ksnowden{at}hortresearch.co.nz).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.106.087957

^* Corresponding author; e-mail ksnowden{at}hortresearch.co.nz; fax 64–9–8154201.

Received August 3, 2006; accepted November 29, 2006; published December 8, 2006.

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