RESUMEN
BACKGROUND: Crossovers are essential for the completion of meiosis. Recently, two pathways of crossover formation have been identified on the basis of distinct genetic controls. In one pathway, crossover inhibits the occurrence of another such event in a distance-dependent manner. This phenomenon is known as interference. The second kind of crossover is insensitive to interference. The two pathways function independently in budding yeast. Only interference-insensitive crossovers occur in Schizosaccharomyces pombe. In contrast, only interference-sensitive crossovers occur in Caenorabditis elegans. The situation in mammals and plants remains unclear. Mer3 is one of the genes shown to be required for the formation of interference-sensitive crossovers in Saccharomyces cerevisiae. RESULTS: To unravel the crossover status in the plant Arabidopsis thaliana, we investigated the role of the A. thaliana MER3 gene through the characterization of a series of allelic mutants. All mer3 mutants showed low levels of fertility and a significant decrease (about 75%) but not a total disappearance of meiotic crossovers, with the number of recombination events initiated in the mutants being similar to that in the wild-type. Genetic analyses showed that the residual crossovers in mer3 mutants did not display interference in one set of adjacent intervals. CONCLUSIONS: Mutation in MER3 in Arabidopsis appeared to be specific to recombination events resulting in interference-sensitive crossovers. Thus, MER3 function is conserved from yeast to plants and may exist in other metazoans. Arabidopsis therefore has at least two pathways for crossover formation, one giving rise to interference-sensitive crossover and the other to independently distributed crossovers.
Asunto(s)
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Cromosomas de las Plantas/genética , Intercambio Genético/fisiología , Meiosis/fisiología , Secuencia de Aminoácidos , Arabidopsis/fisiología , Proteínas de Arabidopsis/fisiología , Secuencia de Bases , Cruzamientos Genéticos , Intercambio Genético/genética , Análisis Citogenético , ADN Helicasas/genética , ADN Helicasas/fisiología , Análisis Mutacional de ADN , Cartilla de ADN , ADN Complementario/genética , Marcadores Genéticos , Microscopía Fluorescente , Datos de Secuencia Molecular , Saccharomyces cerevisiae , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/fisiología , Alineación de Secuencia , Análisis de Secuencia de ADNRESUMEN
A bio-fermentation technique was used for the in vivo diversification of flavonoid structures based on expression in Escherichia coli of six O-methyltransferases (OMTs) from Mentha x piperita and one O-glucosyltransferase (GT) each from Arabidopsis thaliana and Allium cepa. Enzymes were shown to be regio-specific in in vitro experiments and modified a broad range of flavonoid substrates at various positions. Using the flavonol quercetin as a model substrate, we show that the product spectrum produced with the in vivo approach is identical to that found in vitro. Additionally, using mixed cultures of E. coli expressing different classes of modifying genes (OMTs and GTs), the production of polymethylated flavonoid glucosides was observed. This report demonstrates the potential to increase the structural diversity of plant secondary metabolites using a multi-enzyme, bio-fermentation approach.