Gibberellin Regulation of Fruit Set and Growth in Tomato

The role of gibberellins (GAs) in tomato (Solanum lycopersicum) fruit development was investigated. Two different inhibitors of GA biosynthesis (LAB 198999 and paclobutrazol) decreased fruit growth and fruit set, an effect reversed by GA₃ application. LAB 198999 reduced GA₁ and GA₈ content, but incr...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 2007-09, Vol.145 (1), p.246-257
Main Authors: Serrani, Juan Carlos, Sanjuán, Rafael, Ruiz-Rivero, Omar, Fos, Mariano, García-Martínez, José Luis
Format: Article
Language:English
Subjects:
Agronomy. Soil science and plant productions
Biological and medical sciences
Biosynthesis
Cloning, Molecular
Development and Hormone Action
Economic plant physiology
Enzymes
Flowering
Flowers - metabolism
Flowers - physiology
Fructification, ripening. Postharvest physiology
Fruit - growth & development
Fruit set
Fruits
Fundamental and applied biological sciences. Psychology
Genes
Genes, Plant
Gibberellins
Gibberellins - metabolism
Gibberellins - physiology
Growth and development
Lycopersicon esculentum - genetics
Lycopersicon esculentum - growth & development
Lycopersicon esculentum - metabolism
Mixed Function Oxygenases - genetics
Mixed Function Oxygenases - metabolism
Molecular Sequence Data
Ovaries
Phylogeny
Plants
Pollination
Transcription, Genetic
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Summary:The role of gibberellins (GAs) in tomato (Solanum lycopersicum) fruit development was investigated. Two different inhibitors of GA biosynthesis (LAB 198999 and paclobutrazol) decreased fruit growth and fruit set, an effect reversed by GA₃ application. LAB 198999 reduced GA₁ and GA₈ content, but increased that of their precursors GA₅₃, GA₄₄, GA₁₉, and GA₂₀ in pollinated fruits. This supports the hypothesis that GA₁ is the active GA for tomato fruit growth. Unpollinated ovaries developed parthenocarpically in response to GA₃ > GA₁ = GA₄ > GA₂₀, but not to GA₁₉, suggesting that GA 20-oxidase activity was limiting in unpollinated ovaries. This was confirmed by analyzing the effect of pollination on transcript levels of SlCPS, SlGA20ox1, -2, and -3, and SlGA3ox1 and -2, encoding enzymes of GA biosynthesis. Pollination increased transcript content of SlGA20ox1, -2, and -3, and SlCPS, but not of SlGA3ox1 and -2. To investigate whether pollination also altered GA inactivation, full-length cDNA clones of genes encoding enzymes catalyzing GA 2-oxidases (SlGA2ox1, -2, -3, -4, and -5) were isolated and characterized. Transcript levels of these genes did not decrease early after pollination (5-d-old fruits), but transcript content reduction of all of them, mainly of SlGA2ox2, was found later (from 10 d after anthesis). We conclude that pollination mediates fruit set by activating GA biosynthesis mainly through up-regulation of GA20ox. Finally, the phylogenetic reconstruction of the GA2ox family clearly showed the existence of three gene subfamilies, and the phylogenetic position of SlGA2ox1, -2, -3, -4, and -5 was established.
ISSN:0032-0889
1532-2548
1532-2548
DOI:10.1104/pp.107.098335