Gibberellin Regulation of Fruit Set and Growth in Tomato

Abstract

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 GA 3 application. LAB 198999 reduced GA 1 and GA 8 content, but increased that of their precursors GA 53 , GA 44 , GA 19 , and GA 20 in pollinated fruits. This supports the hypothesis that GA 1 is the active GA for tomato fruit growth. Unpollinated ovaries developed parthenocarpically in response to GA 3 . GA 1 5 GA 4 . GA 20 , but not to GA 19 , 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.

Comprehensive Tissue-Specific Transcriptome Analysis Reveals Distinct Regulatory Programs during Early Tomato Fruit Development

“…S6F) are consistent with previous reports of increased bioactive GA content and GA20ox transcription after pollination (Serrani et al, 2007(Serrani et al, , 2008de Jong et al, 2011). However, it was not previously known that a GA20ox transcript increases particularly in the funiculus, which is also a site of high auxin activity (Pattison and Catalá, 2012;Fig.…”

DELLA Signaling Mediates Stress-Induced Cell Differentiation in Arabidopsis Leaves through Modulation of Anaphase-Promoting Complex/Cyclosome Activity

“…Our findings point to GA/DELLA-mediated control of mitotic exit in Arabidopsis leaves as well, at least under stress conditions. Furthermore, our finding that PAC and DELLA stabilization induce endoreduplication is in contrast to earlier observations based on GA addition experiments and mutant analysis showing that GA promotes endoreduplication in, for instance, pea (Pisum sativum; Mohamed and Bopp, 1980), Arabidopsis hypocotyls (Gendreau et al, 1999;Saibo et al, 2003), and tomato (Solanum lycopersicum) fruits (Serrani et al, 2007). This, again, suggests that the effects of hormones depend greatly on concentration, tissue or cell type, species, and environmental parameters.…”

Abscisic acid levels in tomato ovaries are regulated by LeNCED1 and SlCYP707A1

“…For instance, it was shown that expression of a GA 20-oxidase gene was induced by pollination in tomato (Rebers et al 1999;Serrani et al 2007), and the importance of SlDELLA, which represses GA signaling and tomato fruit set, has also been demonstrated (Marti et al 2007). In additional, IAA9 and ARF8, both transcriptional regulators of the auxin response, were shown to be part of an important signal for fruit set (Wang et al 2005;Goetz et al 2007).…”