SHORT VEGETATIVE PHASE reduces gibberellin biosynthesis at the Arabidopsis shoot apex to regulate the floral transition.

In Arabidopsis thaliana environmental and endogenous cues promote flowering by activating expression of a small number of integrator genes. The MADS box transcription factor SHORT VEGETATIVE PHASE (SVP) is a critical inhibitor of flowering that directly represses transcription of these genes. However, we show by genetic analysis that the effect of SVP cannot be fully explained by repressing known floral integrator genes.

The characterization of transgenic tomato overexpressing gibberellin 20-oxidase reveals induction of parthenocarpic fruit growth, higher yield, and alteration of the gibberellin biosynthetic pathway.

Fruit-set and growth in tomato depend on the action of gibberellins (GAs). To evaluate the role of the GA biosynthetic enzyme GA 20-oxidase (GA20ox) in that process, the citrus gene CcGA20ox1 was overexpressed in tomato (Solanum lycopersicum L.) cv Micro-Tom.

Characterization of the procera tomato mutant shows novel functions of the SlDELLA protein in the control of flower morphology, cell division and expansion, and the auxin-signaling pathway during fruit-set and development.

procera (pro) is a tall tomato (Solanum lycopersicum) mutant carrying a point mutation in the GRAS region of the gene encoding SlDELLA, a repressor in the gibberellin (GA) signaling pathway. Consistent with the SlDELLA loss of function, pro plants display a GA-constitutive response phenotype, mimicking wild-type plants treated with GA₃. The ovaries from both nonemasculated and emasculated pro flowers had very strong parthenocarpic capacity, associated with enhanced growth of preanthesis ovaries due to more and larger cells.

Gibberellin A1 metabolism contributes to the control of photoperiod-mediated tuberization in potato.

Some potato species require a short-day (SD) photoperiod for tuberization, a process that is negatively affected by gibberellins (GAs). Here we report the isolation of StGA3ox2, a gene encoding a GA 3-oxidase, whose expression is increased in the aerial parts and is repressed in the stolons after transfer of photoperiod-dependent potato plants to SD conditions. Over-expression of StGA3ox2 under control of constitutive or leaf-specific promoters results in taller plants which, in contrast to StGA20ox1 over-expressers previously reported, tuberize earlier under SD conditions than the controls.

Hormonal regulation of tomato gibberellin 20-oxidase1 expressed in Arabidopsis.

Gibberellin 20-oxidases, enzymes of gibberellin (GA) biosynthesis, play an important role in (GA) homeostasis. To investigate the regulation of tomato SlGA20ox1 expression, a genomic clone was isolated, its promoter transcriptionally fused to the GUS reporter gene, and the construct used to transform Arabidopsis. Expression was found in diverse vegetative (leaves and roots) and reproductive (flowers) organs.

Inhibition of auxin transport from the ovary or from the apical shoot induces parthenocarpic fruit-set in tomato mediated by gibberellins.

Fruit-set in tomato (Solanum lycopersicum) depends on gibberellins and auxins (GAs). Here, we show, using the cv MicroTom, that application of N-1-naphthylphthalamic acid (NPA; an inhibitor of auxin transport) to unpollinated ovaries induced parthenocarpic fruit-set, associated with an increase of indole-3-acetic acid (IAA) content, and that this effect was negated by paclobutrazol (an inhibitor of GA biosynthesis). NPA-induced ovaries contained higher content of GA(1) (an active GA) and transcripts of GA biosynthetic genes (SlCPS, SlGA20ox1, and -2).

Auxin-induced fruit-set in tomato is mediated in part by gibberellins.

Tomato (Solanum lycopersicum L.) fruit-set and growth depend on gibberellins (GAs). Auxins, another kind of hormone, can also induce parthenocarpic fruit growth in tomato, although their possible interaction with GAs is unknown.

Gene expression analysis in citrus reveals the role of gibberellins on photosynthesis and stress.

The effect of gibberellins (GA) on internode transcriptome was investigated in transgenic Carrizo citrange (Citrus sinensis x Poncirus trifoliata) plants overexpressing endogenous CcGA20ox1 (encoding a GA biosynthetic gene), and in non-transformed explants treated with GA(3), using a citrus cDNA microarray. Substantial modulation of gene expression was found in sense CcGA20ox plants. Extensive up-regulation of genes involved in photosynthesis and carbon utilization, and down-regulation of those involved in protein synthesis and ribosome biogenesis were shown for the first time in plants with higher GA content.

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 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.

Overexpression of a protein phosphatase 2C from beech seeds in Arabidopsis shows phenotypes related to abscisic acid responses and gibberellin biosynthesis.

A functional abscisic acid (ABA)-induced protein phosphatase type 2C (PP2C) was previously isolated from beech (Fagus sylvatica) seeds (FsPP2C2). Because transgenic work is not possible in beech, in this study we overexpressed this gene in Arabidopsis (Arabidopsis thaliana) to provide genetic evidence on FsPP2C2 function in seed dormancy and other plant responses. In contrast with other PP2Cs described so far, constitutive expression of FsPP2C2 in Arabidopsis, under the cauliflower mosaic virus 35S promoter, produced enhanced sensitivity to ABA and abiotic stress in seeds and vegetative tissues, dwarf phenotype, and delayed flowering, and all these effects were reversed by gibberellic acid application.

Light Regulation of Gibberellin Biosynthesis and Mode of Action.

Some phenotypic effects produced in plants by light are very similar to those induced by hormones. In this review, the light-gibberellin (GA) interaction in germination, de-etiolation, stem growth, and tuber formation (process regulated by GAs) are discussed. Germination of lettuce and Arabidopsis seeds depends on red irradiation (R), which enhances the expression of GA 3-oxidase genes (GA3ox) and leads to an increase in active GA content.