RESUMEN
Highly organized interphase cortical microtubule (MT) arrays are essential for anisotropic growth of plant cells, yet little is known about the molecular mechanisms that establish and maintain the order of these arrays. The Arabidopsis thaliana spiral1 (spr1) mutant shows right-handed helical growth in roots and etiolated hypocotyls. Characterization of the mutant phenotypes suggested that SPR1 may control anisotropic cell expansion through MT-dependent processes. SPR1 was identified by map-based cloning and found to encode a small protein with unknown function. Proteins homologous to SPR1 occur specifically and ubiquitously in plants. Genetic complementation with green fluorescent protein fusion proteins indicated that the SPR1 protein colocalizes with cortical MTs and that both MT localization and cell expansion control are conferred by the conserved N- and C-terminal regions. Strong SPR1 expression was found in tissues undergoing rapid cell elongation. Plants overexpressing SPR1 showed enhanced resistance to an MT drug and increased hypocotyl elongation. These observations suggest that SPR1 is a plant-specific MT-localized protein required for the maintenance of growth anisotropy in rapidly elongating cells.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/fisiología , Proteínas Asociadas a Microtúbulos/metabolismo , Microtúbulos/fisiología , Arabidopsis/citología , Arabidopsis/genética , Proteínas de Arabidopsis/genética , División Celular , Clonación Molecular , Escherichia coli/genética , Glucuronidasa/genética , Proteínas Asociadas a Microtúbulos/genética , Datos de Secuencia Molecular , Plantas Modificadas Genéticamente , Proteínas Recombinantes/metabolismoRESUMEN
A novel thermo-acidophilic bacterium was isolated from an acidic beverage that had the odour of guaiacol. The cells are aerobic, gram-positive, spore-forming rods. The organism, strain TA-67T, grows at temperatures from 20 to 55 degrees C (optimum, 50 degrees C) and at pH values from 2.5 to 5.5 (optimum, pH 3.0). It possesses omega-cyclohexane fatty acid as a major cellular fatty acid. The G+C content of the DNA is 54.1 mol%. Phylogenetic analysis of the 16S rRNA gene sequences indicated that strain TA-67T constituted a distinct lineage in the Alicyclobacillus cluster, with Alicyclobacillus acidoterrestris as the closest neighbour (96.6% homology). Phenotypically, it is similar to, but can be distinguished from, omega-cyclohexane fatty acid-possessing alicyclobacilIi (A. acidoterrestris, Alicyclobacillus acidocaldarius, Alicyclobacillus hesperidum and 'Alicyclobacillus mali') by the morphology of spores and sporangia, by the growth response to different temperatures, and by the profiles for acid production from carbon sources. It is the alicyclobacillus that produces guaiacol, a causative substance for an 'off' flavour of orange juice. On the basis of the phenotypic and phylogenetic evidence, it is concluded that strain TA-67T represents a new species of the genus Alicyclobacillus, for which the name Alicyclobacillus acidiphilus is proposed. The type strain is TA-67T (= DSM 14558T = IAM 14935T = NRIC 6496T).
Asunto(s)
Bacterias Aerobias/clasificación , Bacterias Aerobias/aislamiento & purificación , Bacilos Grampositivos Formadores de Endosporas/clasificación , Bacilos Grampositivos Formadores de Endosporas/aislamiento & purificación , Bacterias Aerobias/genética , Bacterias Aerobias/metabolismo , Composición de Base , Bebidas/microbiología , ADN Bacteriano/química , ADN Bacteriano/genética , ADN Ribosómico/genética , Ácidos Grasos/análisis , Ácidos Grasos/química , Bacilos Grampositivos Formadores de Endosporas/genética , Bacilos Grampositivos Formadores de Endosporas/metabolismo , Guayacol/metabolismo , Concentración de Iones de Hidrógeno , Datos de Secuencia Molecular , Fenotipo , Filogenia , ARN Bacteriano/genética , ARN Ribosómico 16S/genética , Terminología como AsuntoRESUMEN
A thermo-acidophilic gram-positive bacterium, strain CP-1T, which grows aerobically at 35-65 degrees C (optimum 55-60 degrees C) and at pH 3.5-6.0 (optimum pH 4.5-5.0), was isolated from a herbal tea made from the dried flowers of hibiscus. Phylogenetic analysis of the 16S rRNA gene sequences showed that this bacterium was clearly distinguishable from previously described species of the genera Alicyclobacillus and Sulfobacillus. Strain CP-1T had unique omega-cycloheptane fatty acids as the major membrane lipid component, a characteristic which is peculiar to Alicyclobacillus cycloheptanicus. However, phenotypic and chemotaxonomic characteristics of strain CP-1T were different from those of the type strain of A. cycloheptanicus. DNA-DNA hybridization between the type strains of Alicyclobacillus species and Sulfobacillus disulfidooxidans was <20%, indicating that strain CP-1T represents a distinct species. On the basis of these results, the name Alicyclobacillus herbarius is proposed for this organism. The type strain is strain CP-1T (= DSM 13609T = IAM 14883T = NRIC 0477T).