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Steve J. Croker, Peter Hedden, and Wilhelm Rademacher

Prohexadione-Ca (BAS 125 W) is a new growth retardant for the inhibition of excessive vegetative growth in apple and other plant species. From work with enzyme preparations, it is known that prohexadione-Ca mimics 2-oxoglutaric acid, the co-substrate of dioxygenases, which catalyze late steps in gibberellin (GA) biosynthesis. As a result, the formation of growth-active GAs is reduced. In order to have a better understanding of its effects in intact plants, we have analyzed the GA status of treated and untreated apple plantlets. In a typical experiment, the following results were obtained: Plants (cv. Jonagold on M9 at 19 cm of new shoot growth) were sprayed until run-off with an aqueous preparation containing 25 ppm of active ingredient. After 22 days of cultivation under greenhouse conditions, total new shoot growth of the controls and the treated plants was 55 cm and 44 cm, respectively. In the apical part of this material the following GAs (roughly ordered in biosynthetic sequence) were detected at the following levels (control/treated in microgram per kilogram dry weight): GA19 (31/62), GA29 (24/36), GA20 (11/20), GA1 (4/3), and GA8 (8/3). These results clearly demonstrate that prohexadione-Ca blocks primarily the hydroxylation of GA20 into GA1. This leads to reduced levels of the highly active GA1 and of GA8, its inactive metabolite, whereas GA20 and the other inactive precursors accumulate. The data support older observations obtained in vitro, which indicate that GA20 3β-hydroxylase and related dioxygenases are the primary targets of prohexadione-Ca and similar compounds.

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Nobutaka Shiraiwa, Kaori Kikuchi, Ichiro Honda, Masayoshi Shigyo, Hiroko Yamazaki, Daisuke Tanaka, Kenji Tanabe, and Akihiro Itai

20 to gibberellin A 1 Planta 160 455 463 Itoh, H. Ueguchi-Tanaka, M. Sentoku, N. Kitano, H. Matsuoka, M. Kobayashi, M. 2001 Cloning and functional analysis of two gibberellin 3β-hydroxylase genes that are differently expressed during the growth of

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Steven McArtney, J.D. Obermiller, and A. Green

effects of P-Ca on GA metabolism. P-Ca inhibits several key enzymes involved in GA metabolism, including GA 20 -3β-hydroxylase and certain 2β-hydroxylases ( Rademacher and Kober, 2003 ). GA 20 -3β-hydroxylase is the most important target enzyme inhibited

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Taifeng Zhang, Jiajun Liu, Sikandar Amanullah, Zhuo Ding, Haonan Cui, Feishi Luan, and Peng Gao

; Sun, 1992 ; Winkler, 1995 ) and expressed as mutant genes in different plant types ( Hedden and Phillips, 2001 ). Mainly, GA 3β-hydroxylase catalyzes the absolute activity in the GA biosynthesis pathway ( Yamaguchi, 2008 ), and its pivotal role in

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Paemika Promkaew, Varit Srilaong, Chalermchai Wongs-Aree, Nutthachai Pongprasert, Samak Kaewsuksaeng, and Satoru Kondo

boldface. GGPP = geranylgeranyl diphosphate; PSY = phytoene synthase; PDS = phytoene desaturase; ZDS = ζ-carotene desaturase; ɛ-LCY = lycopene ɛ-cyclase; β-LCY = lycopene β-cyclase; β-CHX = β-carotene hydroxylase; ɛ-CHX = ɛ-carotene hydroxylase; ZEP

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Aneta K. Studzinska, David S. Gardner, James D. Metzger, David Shetlar, Robert Harriman, and T. Karl Danneberger

conversion of GA20 to GA1 × 3-β-hydroxylase, reducing leaf cell elongation ( Adams et al., 1992 ) but not cell division ( Ervin and Koski, 2001 ). However, to ensure consistent and lasting effects, frequent applications of TE are required. In plants

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Jessica G. Barb, Dennis J. Werner, and Robert J. Griesbach

family (Asteraceae) Springer-Verlag Vienna, Austria Britsch, L. Ruhnau-Brich, B. Forkmann, G. 1992 Molecular cloning, sequence analysis, and in vitro expression of flavanone 3β-hydroxylase from Petunia hybrida

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Ni Jia, Qing-Yan Shu, Dan-Hua Wang, Liang-Sheng Wang, Zheng-An Liu, Hong-Xu Ren, Yan-Jun Xu, Dai-Ke Tian, and Kenneth Michael Tilt

anthocyanins detected in most accessions except for the three accessions mentioned previously. It indicated that the enzyme flavonoid 3′-hydroxylase (F3′H) was more competitive in the use of substrate than dihydroflavonol 4-reductase. F3′H catalyzed naringenin

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Shi-Lin Tian, Li Li, Yue-Qin Tian, S.N.M. Shah, and Zhen-Hui Gong

, use of natural pigments in food production is increasing worldwide ( Tian et al., 2014a ). Capsanthin (3,3′-dihydroxy-β, k-caroten-6′-one) is one of the primary ingredients for red pigments. It accumulates in chromoplast thylakoids in the pericarp of

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Robert L. Jarret, Gloria E. Barboza, Fabiane Rabelo da Costa Batista, Terry Berke, Yu-Yu Chou, Amanda Hulse-Kemp, Neftali Ochoa-Alejo, Pasquale Tripodi, Aniko Veres, Carolina Carrizo Garcia, Gabor Csillery, Yung-Kuang Huang, Erzsebet Kiss, Zsofia Kovacs, Mihaly Kondrak, Magda Lisette Arce-Rodriguez, Marisel A. Scaldaferro, and Antal Szoke

, such as normal expression levels of this gene during fruit color development and the existence and normal expression of additional genes such as Psy , lycopene-β-cyclase ( Lycb ), and β-carotene hydroxylase ( CrtZ ), are necessary for red coloration