Chromosome contribution to andean polyploid species of Senecio (Asteraceae), from Argentina

Fil: López, Mariana G.. Lab. de Citogenética y Evol.; Depto. de Ciencias Biológicas; Universidad de Buenos AiresFil: Wulff, Arturo F.. Lab. de Citogenética y Evol.; Depto. de Ciencias Biológicas; Universidad de Buenos AiresFil: Xifreda, Cecilia Carmen. Laboratorio de Etnobotánica y Botánica Aplicada (LEBA); Facultad de Ciencias Naturales y Museo; Universidad Nacional de La Plat

Characterization of quaternary ammonium compounds in Flourensia xerophytic communities and response to UV-B radiation

As part of ongoing studies aimed at characterizing molecular components involved in the ecophysiological adaptations of native xerophytic plants from central Argentina, we demonstrated the presence of compatible solutes in Flourensia campestris (FC) and Flourensia oolepis (FO), specifically glycine betaine (GB) through TLC, LC, 1H NMR and 13C-NMR. GB content (leaves: 38±7μmolg-1 DW; adult plants>seedlings), and distribution (capitula>vegetative leaves>reproductive leaves>shoots>roots) were similar to other quaternary ammonium compound (QAC) accumulators. Flourensia seedlings from both species protected from UV-B exposure - a major abiotic stress in these natural environments - showed a significant increase of GB in the leaves (p<0.01) and a significant decrease in the roots (p<0.05). In FC and FO xerophytic shrub-dominated communities QACs were detected for the first time in 41% of co-occurring species (N=39), 14 of 28 natives (50%) and 2 of 11 exotics (18%), being GB in natives only (57% of QAC accumulators). GB may be considered as a chemotaxonomical character for the genus Flourensia, since it was also detected in Flourensia hirta, Flourensia niederleinii, Flourensia riparia, Flourensia fiebrigii, Flourensia macroligulata and Flourensia heterolepis. Our controlled UV-B experiments, set up in the same natural environment where these species grow, clearly show that solar UV-B - and therefore oxidative stress - is involved in regulating GB contents and within-plant distribution in FC and FO seedlings. The findings in Flourensia co-occurring native species suggest that QACs accumulation may be considered as a community-specific ecophysiological trait in these xerophytic environments. .Fil: Piazza, Leonardo A.. Universidad de Buenos Aires. Facultad de Agronomia. Sede Polo Universitario Punilla Centro; ArgentinaFil: López, D.. Universidad de Buenos Aires. Facultad de Agronomia. Sede Polo Universitario Punilla Centro; ArgentinaFil: Silva, Mariana Paola. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomia. Sede Polo Universitario Punilla Centro; ArgentinaFil: Lopez Rivilli, Marisa Juana. Universidad de Buenos Aires. Facultad de Agronomia. Sede Polo Universitario Punilla Centro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cantero, Juan Jose. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Tourn, G. M.. Universidad de Buenos Aires. Facultad de Agronomia. Sede Polo Universitario Punilla Centro; ArgentinaFil: Scopel, Ana Leonor. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales; Argentin

South African fireweed Senecio madagascariensis (Asteraceae) in Argentina: Relevance of chromosome studies to its systematics

The systematic identity of Senecio madagascariensis is ratified against the opinion that it is conspecific with Senecio inaequidens. Both species are native to South Africa and have been merged in the 'Senecio inaequidens complex', a group of entities difficult to distinguish from each other. Senecio madagascariensis is widespread in South America and Australia, where it is an invasive weed. Mitotic and meiotic studies were conducted on Argentinian material; chromosome counts solved the chromosome number controversy, validating 2n = 20. The karyotype was symmetrical, composed of ten pairs of metacentric chromosomes varying from 1.62 to 2.38 μm in length. The most frequent number of satellited chromosomes was three, but their position was difficult to assign. Meiosis was regular, with a configuration of ten predominantly open bivalents. Univalents and quadrivalents were rarely observed. High frequencies of secondary associations of bivalents, chromosome asynchrony and bivalent grouping were documented, reinforcing the hypothesis that x = 5 is the basic chromosome number. Pollen stainability ranged from 94 to 99%. The relevance of chromosomal studies in the circumscription of S. madagascariensis is discussed. Hybridization and polyploidy, as principal evolutionary forces in this genus, explain the systematic difficulties.Facultad de Ciencias Naturales y Muse

South African fireweed Senecio madagascariensis (Asteraceae) in Argentina: Relevance of chromosome studies to its systematics

The systematic identity of Senecio madagascariensis is ratified against the opinion that it is conspecific with Senecio inaequidens. Both species are native to South Africa and have been merged in the 'Senecio inaequidens complex', a group of entities difficult to distinguish from each other. Senecio madagascariensis is widespread in South America and Australia, where it is an invasive weed. Mitotic and meiotic studies were conducted on Argentinian material; chromosome counts solved the chromosome number controversy, validating 2n = 20. The karyotype was symmetrical, composed of ten pairs of metacentric chromosomes varying from 1.62 to 2.38 μm in length. The most frequent number of satellited chromosomes was three, but their position was difficult to assign. Meiosis was regular, with a configuration of ten predominantly open bivalents. Univalents and quadrivalents were rarely observed. High frequencies of secondary associations of bivalents, chromosome asynchrony and bivalent grouping were documented, reinforcing the hypothesis that x = 5 is the basic chromosome number. Pollen stainability ranged from 94 to 99%. The relevance of chromosomal studies in the circumscription of S. madagascariensis is discussed. Hybridization and polyploidy, as principal evolutionary forces in this genus, explain the systematic difficulties.Facultad de Ciencias Naturales y Muse

Chromosome numbers and meiotic studies in species of Senecio (Asteraceae) from Argentina

Meiotic chromosome counts, chromosomal behaviour and meiotic configurations of ten taxa of Senecio from Argentina were examined. Most counts are original: S. crepidifolius DC., S. francisci Phil. and S. octolepis Griseb. var. saltensis (Hicken) Cabrera & Zardini have 2n = 40, and S. chrysolepis Phil., 2n = 80 + 8B. We confirmed previous reports for S. deferens Griseb. (2n = 40 + 4B), S. filaginoides DC. var. filaginoides (2n = 40), S. hieronymi Griseb. (2n = 40 + 7B), S. pampeanus Cabrera (2n = 40) and S. rudbeckiifolius Meyen & Walp. (2n = 40 + 7B). In S. bracteolatus Hook. & Arn. var. bracteolatus, we found a new number (2n = 40) that differs from the one cited previously. In four species, numerical polymorphisms for B-chromosomes were observed. Several of the analysed species presented secondary bivalent association. This phenomenon, together with other evidence, supports x = 5 as the basic chromosome number. The number of chiasmata and their positions were also surveyed, with the finding that open bivalents were the most frequent meiotic figures and terminal chiasmata the preferential position. These features are related to recombination rate, and the success and persistence of these polyploids. We discuss some systematic and evolutionary aspects in the light of cytogenetic data and conclude that polyploidy is the major force modelling the chromosome evolution within this genus. Laboratorio de Etnobotánica y Botánica Aplicad

Secondary metabolites from two species of Tolpis and their biological activities

Phytochemical research of two Tolpis species, T. proustii and T. lagopoda, led to the isolation of three new compounds: 30-chloro-3β-acetoxy-22α-hydroxyl-20(21)- taraxastene (1), 3β,22α-diacetoxy-30-ethoxy-20(21)-taraxastene (2) and 3β,28-dihydroxy11α-hydroperoxy-12-ursene (3). The structures of the new compounds were elucidated by means of extensive IR, NMR, and MS data and by comparison of data reported in the literature. The in vitro antioxidant activities of the extracts were assessed by the DPPH and ABTS scavenging methods. The cytotoxicity of several known compounds and its derivatives was also assessed against human myeloid leukemia K-562 and K-562/ADR cell lines.This work was supported by a Grant from the Ministry of Science of Spain and Innovation and from the European Regional Development Fund (SAF2010-21380) to F.E, Instituto Canario de Investigación del Cáncer to F.L. and Agencia Canaria de Investigación, Innovación y Sociedad de la Información (FEDER) (C200801000174) to J.T. F.L. was supported by JAE-doctoral Program from the Ministerio de Ciencia e Innovación.Peer reviewe

Chromosome numbers and meiotic studies in species of Senecio (Asteraceae) from Argentina

Meiotic chromosome counts, chromosomal behaviour and meiotic configurations of ten taxa of Senecio from Argentina were examined. Most counts are original: S. crepidifolius DC., S. francisci Phil. and S. octolepis Griseb. var. saltensis (Hicken) Cabrera & Zardini have 2n = 40, and S. chrysolepis Phil., 2n = 80 + 8B. We confirmed previous reports for S. deferens Griseb. (2n = 40 + 4B), S. filaginoides DC. var. filaginoides (2n = 40), S. hieronymi Griseb. (2n = 40 + 7B), S. pampeanus Cabrera (2n = 40) and S. rudbeckiifolius Meyen & Walp. (2n = 40 + 7B). In S. bracteolatus Hook. & Arn. var. bracteolatus, we found a new number (2n = 40) that differs from the one cited previously. In four species, numerical polymorphisms for B-chromosomes were observed. Several of the analysed species presented secondary bivalent association. This phenomenon, together with other evidence, supports x = 5 as the basic chromosome number. The number of chiasmata and their positions were also surveyed, with the finding that open bivalents were the most frequent meiotic figures and terminal chiasmata the preferential position. These features are related to recombination rate, and the success and persistence of these polyploids. We discuss some systematic and evolutionary aspects in the light of cytogenetic data and conclude that polyploidy is the major force modelling the chromosome evolution within this genus. Laboratorio de Etnobotánica y Botánica Aplicad

South African fireweed Senecio madagascariensis (Asteraceae) in Argentina: Relevance of chromosome studies to its systematics

The systematic identity of Senecio madagascariensis is ratified against the opinion that it is conspecific with Senecio inaequidens. Both species are native to South Africa and have been merged in the 'Senecio inaequidens complex', a group of entities difficult to distinguish from each other. Senecio madagascariensis is widespread in South America and Australia, where it is an invasive weed. Mitotic and meiotic studies were conducted on Argentinian material; chromosome counts solved the chromosome number controversy, validating 2n = 20. The karyotype was symmetrical, composed of ten pairs of metacentric chromosomes varying from 1.62 to 2.38 μm in length. The most frequent number of satellited chromosomes was three, but their position was difficult to assign. Meiosis was regular, with a configuration of ten predominantly open bivalents. Univalents and quadrivalents were rarely observed. High frequencies of secondary associations of bivalents, chromosome asynchrony and bivalent grouping were documented, reinforcing the hypothesis that x = 5 is the basic chromosome number. Pollen stainability ranged from 94 to 99%. The relevance of chromosomal studies in the circumscription of S. madagascariensis is discussed. Hybridization and polyploidy, as principal evolutionary forces in this genus, explain the systematic difficulties.Facultad de Ciencias Naturales y Muse

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