Characterization of the nuclear ribosomal DNA unit in Oxalis tuberosa (Oxalidacea) and related species

Oxalis tuberosa is an octoploid Andean tuber crop called "oca" that belongs to the worldwide distributed genus Oxalis . The genus is very heterogeneous and its systematics is still problematic. It has been proposed that O. tuberosa evolved by polyploidization of a still not defined ancestor that belongs to an alliance of species sharing the same basic chromosome number (x = 8). Nuclear rDNA units of O. tuberosa and a selected group of four related diploid species were characterised by RFLP using different restriction endonucleases and southern hybridization probes to produce a restriction map for EcoRI and BamHI. The major rDNA unit length in O. tuberosa was estimated at 10.7 kbp. As expected, restriction site variation was observed mainly in the intergenic spacer (IGS), but was also detected in coding regions. Restriction site mapping organization of the transcribed rDNA unit of O. tuberosa is very similar to O. oblongiformis. Nucleotide sequencing of a region of O. peduncularis IGS generated a complex organization pattern of repeats and subrepeats. Diploid species O. peduncularis, O. tabaconasensis and O. aff. villosula exhibited a ladder pattern that is a consequence of a 170 bp subrepeat unit indicating that these species share organization similarity and sequence homology. The variation pattern provided information to compare among diploid species, although it did not help to clarify taxonomic relationships between O. tuberosa and the putative diploid ancestors analysed in this study. Nonetheless, the RFLP pattern exhibited by O. tuberosa for the IGS region was quite unique and will be a useful tool to prospect in other related species

Characterization of the nuclear ribosomal DNA unit in Oxalis tuberosa (Oxalidacea) and related species

Oxalis tuberosa is an octoploid Andean tuber crop called "oca" that belongs to the worldwide distributed genus Oxalis . The genus is very heterogeneous and its systematics is still problematic. It has been proposed that O. tuberosa evolved by polyploidization of a still not defined ancestor that belongs to an alliance of species sharing the same basic chromosome number (x = 8). Nuclear rDNA units of O. tuberosa and a selected group of four related diploid species were characterised by RFLP using different restriction endonucleases and southern hybridization probes to produce a restriction map for EcoRI and BamHI. The major rDNA unit length in O. tuberosa was estimated at 10.7 kbp. As expected, restriction site variation was observed mainly in the intergenic spacer (IGS), but was also detected in coding regions. Restriction site mapping organization of the transcribed rDNA unit of O. tuberosa is very similar to O. oblongiformis. Nucleotide sequencing of a region of O. peduncularis IGS generated a complex organization pattern of repeats and subrepeats. Diploid species O. peduncularis, O. tabaconasensis and O. aff. villosula exhibited a ladder pattern that is a consequence of a 170 bp subrepeat unit indicating that these species share organization similarity and sequence homology. The variation pattern provided information to compare among diploid species, although it did not help to clarify taxonomic relationships between O. tuberosa and the putative diploid ancestors analysed in this study. Nonetheless, the RFLP pattern exhibited by O. tuberosa for the IGS region was quite unique and will be a useful tool to prospect in other related species

Identificación molecular de patrones genéticos en distintas muestras de arándano (vaccinium sp.)

La calidad genotípica de las variedades comerciales de arándano (particularmente diferenciación y homogeneidad) fueron evaluadas mediante la técnica de marcadores moleculares RAPD (polimorfismo de ADN amplificado aleatoriamente) con el objeto de identificar la presencia de genotipos adventicios. El patrón genético generado por RAPD fue reproducible y no mostró diferencias entre ADN extraído de una muestra de arándano micropropagado in vitro o de hojas de plantas adultas, tanto en la variedad Misty como en la O´Neal, evidenciando la ausencia de posibles efectos groseros de variación somaclonal debidos al cultivo de tejidos. Los oligonucleótidos de la serie Operon llamados AB-03, AB-04, AB-05, AB-06, AB-07, AB-09, AB-11 y AB-14, utilizados para el análisis de RAPD, revelaron un total de 40 bandas electroforéticas de ADN polimórfico informativo, confir- mando su utilidad para la identificación y diferenciación de variedades. A partir de los datos de RAPDs obtenidos se realizó un análisis de agrupamiento que reveló dos grupos: uno conteniendo a las muestras pertenecientes a la variedad Misty y otro grupo a las muestras de la variedad O´Neal. Dentro de cada uno de estos grupos, no se encontraron diferencias entre el material in vitro y el de campo, agrupándose con un coeficiente de similitud de 1. El análisis de una muestra adventicia presente en material catalogado como ONeal mostró patrones de amplificación de RAPD muy diferentes, y a través del análisis de agrupamiento se demostró que no se asociaba a ninguno de los dos grupos definidos por las variedades empleadas como testigo. De esta manera, se demuestra la utilidad de los marcadores RAPD en la diferenciación e identificación de variedades de arándano de importancia comercial en la Argentina y la detección, mediante esta metodología, de materiales fuera de tipo de la especie

Virus infection elevates transcriptional activity of miR164a promoter in plants

Background. Micro RNAs (miRs) constitute a large group of endogenous small RNAs that have crucial roles in many important plant functions. Virus infection and transgenic expression of viral proteins alter accumulation and activity of miRs and so far, most of the published evidence involves post-transcriptional regulations. Results. Using transgenic plants expressing a reporter gene under the promoter region of a characterized miR (P-miR164a), we monitored the reporter gene expression in different tissues and during Arabidopsis development. Strong expression was detected in both vascular tissues and hydathodes. P-miR164a activity was developmentally regulated in plants with a maximum expression at stages 1.12 to 5.1 (according to Boyes, 2001) along the transition from vegetative to reproductive growth. Upon quantification of P-miR164a-derived GUS activity after Tobacco mosaic virus Cg or Oilseed rape mosaic virus (ORMV) infection and after hormone treatments, we demonstrated that ORMV and gibberellic acid elevated P-miR164a activity. Accordingly, total mature miR164, precursor of miR164a and CUC1 mRNA (a miR164 target) levels increased after virus infection and interestingly the most severe virus (ORMV) produced the strongest promoter induction. Conclusion. This work shows for the first time that the alteration of miR pathways produced by viral infections possesses a transcriptional component. In addition, the degree of miR alteration correlates with virus severity since a more severe virus produces a stronger P-miR164a induction. © 2009 Bazzini et al; licensee BioMed Central Ltd.Fil:Bazzini, A.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Almasia, N.I. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Mongelli, V.C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Maroniche, G.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Rodriguez, M.C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Distéfano, A.J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Hopp, H.E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Del Vas, M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Asurmendi, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Quantitative Evaluation of Genetic Diversity in Wheat Germplasm Using Molecular Markers

Characterization of germplasm by means of DNA fingerprinting techniques provides a tool for precise germplasm identification and a quantitative estimate of genetic diversity. This estimate is important because a decrease in genetic variability might result in a reduction of the plasticity of the crops to respond to changes in climate, pathogen populations, or agricultural practices. In this study, 105 Argentine bread wheat (Triticum aestivum L.) cultivars released between 1932 and 1995 were characterized by simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers. A selected subset of 10 highly informative SSR was used to construct an Identification Matrix that allowed the discrimination of the 105 cultivars. Data obtained from SSR markers were complemented by information derived from AFLPs. Molecular data were used to quantify genetic diversity across Argentine wheat breeding programs and to determine if modern wheat cultivars have a lower genetic diversity than earlier cultivars (genetic erosion). No significant differences in genetic diversity were found among the large private and public breeding programs, suggesting that each of them contains a representative sample of the complete diversity of the Argentine germplasm. Significant differences were found for both SSR and AFLP only between breeding programs with large differences in number of released cultivars. No significant differences in genetic diversity were found between the group of cultivars released before 1960 and those released in each of the following three decades. Average diversity values based on SSR markers were almost identical for the four analyzed periods. Genetic diversity estimates based on AFLP data confirmed the absence of a reduction of genetic diversity with time, but significant differences (P = 0.01) were found between bread wheat cultivars released in the 1970s (PIC = 0.28) and those released in the 1980s (PIC = 0.34). These results show that the Argentine bread wheat germplasm has maintained a relatively constant level of genetic diversity during the last half century