RESUMO
Cytokinins (CKs) are thought to play important roles in fruit development, especially cell division. However, the mechanisms and regulation of CK activity have not been well investigated. This study analysed CK concentrations and expression of genes involved in CK metabolism in developing tomato (Solanum lycopersicum) ovaries. The concentrations of CK ribosides and isopentenyladenine and the transcript levels of the CK biosynthetic genes SlIPT3, SlIPT4, SlLOG6, and SlLOG8 were high at anthesis and decreased immediately afterward. In contrast, trans-zeatin concentration and the transcript levels of the CK biosynthetic genes SlIPT1, SlIPT2, SlCYP735A1, SlCYP735A2, and SlLOG2 increased after anthesis. The expression of type-A response regulator genes was high in tomato ovaries from pre-anthesis to early post-anthesis stages. These results suggest that the CK signal transduction pathway is active in the cell division phase of fruit development. This study also investigated the effect of CK application on fruit set and development. Application of a synthetic CK, N-(2-chloro-pyridin-4-yl)-N'-phenylurea (CPPU), to unpollinated tomato ovaries induced parthenocarpic fruit development. The CPPU-induced parthenocarpic fruits were smaller than pollinated fruits, because of reduction of pericarp cell size rather than reduced cell number. Thus, CPPU-induced parthenocarpy was attributable to the promotion of cell division, not cell expansion. Overall, the results provide evidence that CKs are involved in cell division during development of tomato fruit.
Assuntos
Citocininas/metabolismo , Frutas/crescimento & desenvolvimento , Proteínas de Plantas/genética , Solanum lycopersicum/crescimento & desenvolvimento , Ciclo Celular , Divisão Celular , Citocininas/genética , Citocininas/isolamento & purificação , Citocininas/farmacologia , Frutas/genética , Frutas/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Solanum lycopersicum/citologia , Solanum lycopersicum/efeitos dos fármacos , Solanum lycopersicum/genética , Modelos Biológicos , Dados de Sequência Molecular , Filogenia , Proteínas de Plantas/metabolismo , Polinização , RNA de Plantas/genética , ReproduçãoRESUMO
DELLA proteins are negative regulators of the signaling of gibberellin (GA), a phytohormone regulating plant growth. DELLA degradation is triggered by its interaction with GID1, a soluble GA receptor, in the presence of bioactive GA. We isolated cDNA from a spliced variant of LsDELLA1 mRNA in lettuce, and named it LsDELLA1sv. It was deduced that LsDELLA1sv encodes truncated LsDELLA1, which has DELLA and VHYNP motifs at the N terminus but lacks part of the C-terminal GRAS domain. The recombinant LsDELLA1sv protein interacted with both Arabidopsis GID1 and lettuce GID1s in the presence of GA. A yeast two-hybrid assay suggested that LsDELLA1sv interacted with LsDELLA1. The ratio of LsDELLA1sv to LsDELLA1 transcripts was higher in flower samples at the late reproductive stage and seed samples (dry seeds and imbibed seeds) than in the other organ samples examined. This study suggests that LsDELLA1sv is a possible modulator of GA signaling in lettuce.
Assuntos
Giberelinas/metabolismo , Lactuca/citologia , Lactuca/metabolismo , Proteínas de Plantas/metabolismo , Transdução de Sinais , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , DNA Complementar/genética , Regulação da Expressão Gênica de Plantas , Lactuca/genética , Dados de Sequência Molecular , Proteínas de Plantas/química , Proteínas de Plantas/genética , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Receptores de Superfície Celular/metabolismoRESUMO
High temperature-induced bolting of lettuce is undesirable agriculturally, making it important to find the mechanism governing the transition from vegetative to reproductive growth. FLOWERING LOCUS T (FT) genes play important roles in the induction of flowering in several plant species. To clarify floral induction in lettuce, we isolated the FT gene (LsFT) from lettuce. Sequence analysis and phylogenetic relationships of LsFT revealed considerable homology to FT genes of Arabidopsis, tomato, and other species. LsFT induced early flowering in transgenic Arabidopsis, but was not completely effective compared to AtFT. LsFT mRNA was abundant in the largest leaves under flowering-inducible conditions (higher temperatures). Gene expression was correlated with flower differentiation of the shoot apical meristem. Our results suggest that LsFT is a putative FT homolog in lettuce that regulates flower transition, similar to its homolog in Arabidopsis. This is the first information on the lettuce floral gene for elucidating regulation of the flowering transition in lettuce.
Assuntos
Regulação da Expressão Gênica no Desenvolvimento/genética , Regulação da Expressão Gênica de Plantas/genética , Lactuca/metabolismo , Proteínas de Plantas/metabolismo , Sequência de Aminoácidos , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Sequência de Bases , DNA de Plantas/genética , Flores/genética , Flores/crescimento & desenvolvimento , Flores/metabolismo , Genes de Plantas/genética , Lactuca/genética , Lactuca/crescimento & desenvolvimento , Meristema/genética , Meristema/crescimento & desenvolvimento , Meristema/metabolismo , Dados de Sequência Molecular , Filogenia , Folhas de Planta/genética , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Proteínas de Plantas/genética , Caules de Planta/genética , Caules de Planta/crescimento & desenvolvimento , Caules de Planta/metabolismo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , RNA Mensageiro/genética , RNA de Plantas/genética , Alinhamento de Sequência , Análise de Sequência de DNARESUMO
Bolting of lettuce is promoted by high temperatures. Gibberellins (GAs) play an important role in the bolting of several plant species, and it has been reported that exogenous GAs induce bolting and early flowering in lettuce. To clarify the role of GAs in this process, we examined the expression of genes involved in GA metabolism (LsGA20ox-1 and -2, LsGA3ox-1 and -2, and LsGA2ox-1 and -2) and endogenous GAs in lettuce stems. Quantitative reverse-transcription PCR indicated that the expression of a GA 3-oxidase gene, LsGA3ox1, is significantly upregulated by high (35/25 degrees C) temperature compared to low (25/15 degrees C) temperature, whereas transcription of the GA 20-oxidase gene, which is upregulated in long-day conditions in arabidopsis and spinach during bolting, is not clearly affected. Quantification of GA by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) showed that high temperature also upregulates the content of GA(1), a bioactive GA in lettuce. Our results suggest that LsGA3ox1 is a candidate for the gene responsible for the increase in GA(1) during lettuce bolting at high temperatures.
