Las papas silvestres y el concepto de especie

Estamos acostumbrados a oír de hablar de especies de plantas y animales. Pero ese concepto resulta difícil de aplicar a muchos organismos, entre ellos las papas silvestres cuyos descendientes domesticados alimentan al mundoFil: Camadro, Elsa Lucila. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce; Argentina. Universidad Nacional de Mar del Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Viabilidad de polen e irregularidades meióticas en una colección de stevia rebaudiana (Bertoni) Bertoni cultivada en Tucumán, Argentina

Stevia rebaudiana (Bertoni) Bertoni (2n=2x=22) (Asteraceae family) is a species of economic value due to the presence of steviol glycosides in leaves -mainly stevioside and rebaudioside A- which are non-caloric sugars. In 2013, a collection of plants (genotypes) from four contrasting environments was established in Tucuman, Argentina, for evaluation under local conditions and, eventually, breeding purposes. As a first step, pollen viability and meiosis was studied in a sample of 56 plants. The percentage of pollen viability varied from medium (69.4%) to high (99.6%) in 52 of them, but from low (36.5%) to relatively low (51.5%) in the remaining four. The latter four plants also presented pollen grains of heterogeneous size, which were classified as n (normal, the most frequent size in the sample), n. Abnormalities were observed in meiosis and at the tetrad stage. Pollen viability appears not to be a problem for planning crossing experiments within the collection. Moreover, the observation of parallel spindles at Anaphase II and dyads and triads at the tetrad stage entails the possibility of eventually exploring ploidy manipulations in breeding.Stevia rebaudiana (Bertoni) Bertoni (2n=2x=22) (familia Asteraceae) es una especie de valor economico debido a la presencia de glucosidos de esteviol en sus hojas, principalmente esteviosido y rebaudiosido A, que son azucares no caloricos. En 2013, se establecio una coleccion de plantas (genotipos) provenientes de cuatro ambientes contrastantes en Tucuman, Argentina, para su evaluacion en condiciones locales y, eventualmente, con fines de mejoramiento genetico. Como primer paso, se estudio la viabilidad del polen y la meiosis en una muestra de 56 plantas. El porcentaje de viabilidad del polen fue de medio (69,4%) a alto (99,6%) en 52 de ellas, pero de bajo (36,5%) a relativamente bajo (51,2%) en las cuatro restantes. Las ultimas cuatro plantas tambien presentaron granos de polen de tamano heterogeneo, que se clasificaron como n (normal, el tamano mas frecuente en la muestra), n. Se observaron anomalias en la meiosis y en el estadio de tetrada. La viabilidad del polen no parece ser un problema para planificar cruzamientos experimentales en la coleccion. Ademas, la observacion de husos paralelos en Anafase II de diadas y triadas en la etapa de tetrada conlleva la posibilidad de explorar, eventualmente, manipulaciones de ploidia en el mejoramiento de esta especie.Fil: Budeguer, Carlos Jorge. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Camadro, Elsa Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Instituto Nacional de Tecnología Agropecuaria; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Erazzo, L. E.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucuman-Santiago del Estero; Argentin

Relevance of the genetic structure of natural populations, sampling and classification approaches for conservation and use of wild crop relatives: potatoes as an example

Crop wild relatives (CWRs) are wild taxa with close genetic relationships to species with direct socioeconomic importance. As essential components of natural habitats and agricultural systems, their conservation and sustainable use are vital. CWRs are ex situ conserved in germplasm banks as samples of natural populations (accessions). Most accessions have been assigned specific status according to the Taxonomic Species Concept, which presupposes that living organisms are at the end of speciation. Thus, the morphological and genetic variability that could be encountered in natural populations is disregarded, negatively affecting conservation of allelic frequencies and effective use in breeding. Passport information usually contains collection date and geographical data, but not reproductive behavior of the sampled population (which defines its genetic structure) and sampling strategies. For ex situ multiplications of original collections, no information is provided on the effectively used strategies. As information on how accessions were composed is lacking, conservation of the allelic frequencies from the originally sampled populations is unknown. Knowledge of reproductive biology of plant populations is of utmost importance to understanding their natural morphological and molecular variability and to developing appropriate methodological approaches for sampling, classifying, and ex situ multiplying to conserve gene frequencies for basic and applied purposes.Les parents sauvages des cultures (PSCs) sont des taxons naturels étroitement reliés, génétiquement, aux espèces d’importance socio-économique directe. Comme composantes essentielles des habitats naturels et des systèmes agricoles, leur conservation et leur utilisation durable sont vitales. On conserve les PSCs ex situ dans des banques de germplasmes comme échantillons des populations naturelles (accessions). On assigne a` la plupart des accessions un statut spécifique selon le concept des espèces taxonomiques, ce qui présuppose que les organismes vivants constituent le terme de la spéciation. Ainsi, la variabilité morphologique et génétique qu’on pourrait rencontrer dans les populations naturelles n’est pas considérée, ce qui affecte négativement la conservation des fréquences alléliques et leur utilisation efficace en amélioration génétique. L’information des passes ports comporte généralement les données des récoltes et les données géographiques, sans référence au comportement reproductif de la population échantillonnée (définissant sa structure génétique) ni aux stratégies d’échantillonnage. Pour les multiplications ex situ des collections originales, il n’existe aucune information sur les stratégies effectivement utilisées. En absence d’information sur la façon selon laquelle on compose les accessions, on ignore la conservation des fréquences alléliques existantes dans les populations originalement échantillonnées. La connaissance de la biologie reproductive des populations de plantes revêt la plus grande importance pour comprendre leur variabilité morphologique et moléculaire et pour développer des approches méthodologiques d’échantillonnage ainsi que la classification et la multiplication ex situ, afin de conserver les fréquences des gènes pour des fins fondamentales et appliquées.Fil: Camadro, Elsa Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentin

Pollen viability and meiotic abnormalities in brome grasses (Bromus L., section Ceratochloa) from Argentina

Bromus Section Ceratochloa includes temperate forage species. South American species form a morphologically very variable hexaploid complex (2n = 6x = 42), with a controversial taxonomic classification. Reproductive biology has been studied in several of them, but the number of analyzed plants has seldom been reported. Further investigations might clarify breeding relations and the adequacy of current classifications. Pollen viability and size, which can provide evidence of spontaneous hybridization, were studied in seven accessions (six plants/accession) classified as B. catharticus var. catharticus, var. elata, and var. rupestris; B. parodii; B. bonariensis; B. lithobius; and B. coloratus. Variability was detected among accessions for average pollen viability (54%–82%) and pollen size (15.8%– 26.2% n.). Meiotic analyses were performed in a sample of genotypes from five accessions with <70% pollen viability and/or variability in pollen size. Normal and abnormal meiocytes (11.9%–44.5%) were recorded at various meiotic stages in one randomly taken genotype from each sample. Since these cleistogamous species can produce chasmogamous flowers, the analyzed accessions, conserved as “species”, are apparently of hybrid origin. Segregation in hybrid populations could add to the confusion in taxonomy, affecting both conservation of genetic diversity and efficiency of parental selection in breeding.Fil: Leofanti, Gabriela Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Camadro, Elsa Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentin

Epigenetic consequences of interploidal hybridisation in synthetic and natural interspecific potato hybrids

Interploidal hybridisation can generate changes in plant chromosome numbers, which might exert effects additional to the expected due to genome merger per se (i.e., genetic, epigenetic and phenotypic novelties).Wild potatoes are suitable to address this question in an evolutionary context. To this end, we performed genetic (AFLP and SSR), epigenetic (MSAP), and cytological comparisons in: i) natural populations of the diploid cytotype of the hybrid taxonomic species Solanum x rechei (2n=2x, 3x) and its parental species, the triploid cytotype of Solanum microdontum (2n=2x, 3x) and Solanum kurtzianum (2n=2x); and ii) newly synthesised intraploidal (2x x 2x) and interploidal (3x x 2x) S. microdontum x S. kurtzianum hybrids.Aneuploidy was detected in S. x rechei and the synthetic interploidal progeny; this phenomenon might have originated the significantly higher number of methylation changes observed in the interploidal vs. the intraploidal hybrids. The wide epigenetic variability induced by interploidal hybridisation is consistent with the novel epigenetic pattern established in S. x rechei compared to its parental species in nature.These results suggest that aneuploid potato lineages can persist throughout the short term, and possibly medium term, and that differences in parental ploidy resulting in aneuploidy are an additional source of epigenetic variation.Fil: Cara, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; ArgentinaFil: Ferrer, María Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; ArgentinaFil: Masuelli, Ricardo Williams. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; ArgentinaFil: Camadro, Elsa Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata; ArgentinaFil: Marfil, Carlos Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentin

A Boolean probabilistic model of metabolic adaptation to oxygen in relation to iron homeostasis and oxidative stress

<p>Abstract</p> <p>Background</p> <p>In aerobically grown cells, iron homeostasis and oxidative stress are tightly linked processes implicated in a growing number of diseases. The deregulation of iron homeostasis due to gene defects or environmental stresses leads to a wide range of diseases with consequences for cellular metabolism that remain poorly understood. The modelling of iron homeostasis in relation to the main features of metabolism, energy production and oxidative stress may provide new clues to the ways in which changes in biological processes in a normal cell lead to disease.</p> <p>Results</p> <p>Using a methodology based on probabilistic Boolean modelling, we constructed the first model of yeast iron homeostasis including oxygen-related reactions in the frame of central metabolism. The resulting model of 642 elements and 1007 reactions was validated by comparing simulations with a large body of experimental results (147 phenotypes and 11 metabolic flux experiments). We removed every gene, thus generating <it>in silico </it>mutants. The simulations of the different mutants gave rise to a remarkably accurate qualitative description of most of the experimental phenotype (overall consistency > 91.5%). A second validation involved analysing the anaerobiosis to aerobiosis transition. Therefore, we compared the simulations of our model with different levels of oxygen to experimental metabolic flux data. The simulations reproducted accurately ten out of the eleven metabolic fluxes. We show here that our probabilistic Boolean modelling strategy provides a useful description of the dynamics of a complex biological system. A clustering analysis of the simulations of all <it>in silico </it>mutations led to the identification of clear phenotypic profiles, thus providing new insights into some metabolic response to stress conditions. Finally, the model was also used to explore several new hypothesis in order to better understand some unexpected phenotypes in given mutants.</p> <p>Conclusions</p> <p>All these results show that this model, and the underlying modelling strategy, are powerful tools for improving our understanding of complex biological problems.</p

Phenotypic instability and epigenetic variability in a diploid potato of hybrid origin, Solanum ruiz-lealii

<p>Abstract</p> <p>Background</p> <p>The wild potato <it>Solanum ruiz-lealii </it>Brüch. (2n = 2x = 24), a species of hybrid origin, is endemic to Mendoza province, Argentina. Recurrent flower malformations, which varied among inflorescences of the same plant, were observed in a natural population. These abnormalities could be the result of genomic instabilities, nucleus-cytoplasmic incompatibility or epigenetic changes. To shed some light on their origin, nuclear and mitochondrial DNA of plants with normal and plants with both normal and malformed flowers (from here on designated as plants with normal and plants with abnormal flower phenotypes, respectively) were analyzed by AFLP and restriction analyses, respectively. Also, the wide genome methylation status and the level of methylation of a repetitive sequence were studied by MSAP and Southern blots analyses, respectively.</p> <p>Results</p> <p>AFLP markers and restriction patterns of mitochondrial DNA did not allow the differentiation of normal from abnormal flower phenotypes. However, methylation patterns of nuclear DNA discriminated normal and abnormal flower phenotypes into two different groups, indicating that abnormal phenotypes have a similar methylation status which, in turn, was different from the methylation patterns of normal phenotypes. The abnormal flower phenotype was obtained by treating a normal plant with 5-Azacytidine, a demethylating agent, giving support to the idea of the role of DNA methylation in the origin of flower abnormalities. In addition, the variability detected for DNA methylation was greater than the detected for nucleotide sequence.</p> <p>Conclusion</p> <p>The epigenetic nature of the observed flower abnormalities is consistent with the results and indicates that in the diploid hybrid studied, natural variation in methylation profiles of anonymous DNA sequences could be of biological significance.</p

Inactivation of mitochondrial aspartate aminotransferase contributes to the respiratory deficit of yeast frataxin-deficient cells

International audienceFriedreich's ataxia is a hereditary neurodegenerative disease caused by reduced expression of mitochondrial frataxin. Frataxin deficiency causes impairment in respiratory capacity, disruption of iron homoeostasis and hypersensitivity to oxidants. Although the redox properties of NAD (NAD + and NADH) are essential for energy metabolism, only few results are available concerning homoeostasis of these nucleotides in frataxin-deficient cells. In the present study, we show that the malate-aspartate NADH shuttle is impaired in Saccharomyces cerevisiae frataxin-deficient cells (yfh1) due to decreased activity of cytosolic and mitochondrial isoforms of malate dehydrogenase and to complete inactivation of the mitochondrial aspartate aminotransferase (Aat1). A considerable decrease in the amount of mitochondrial acetylated proteins was observed in the yfh1 mutant compared with wild-type. Aat1 is acetylated in wild-type mitochondria and deacetylated in yfh1 mitochondria suggesting that inactivation could be due to this post-translational modification. Mutants deficient in iron-sulfur cluster assembly or lacking mitochondrial DNA also showed decreased activity of Aat1, suggesting that Aat1 inactivation was a secondary phenotype in yfh1 cells. Interestingly, deletion of the AAT1 gene in a wild-type strain caused respiratory deficiency and disruption of iron homoeostasis without any sensitivity to oxidative stress. Our results show that secondary inactivation of Aat1 contributes to the amplification of the respiratory defect observed in yfh1 cells. Further implication of mitochondrial protein deacetylation in the physiology of frataxin-deficient cells is anticipated

Friedreich's ataxia: the vicious circle hypothesis revisited

Friedreich's ataxia, the most frequent progressive autosomal recessive disorder involving the central and peripheral nervous systems, is mostly associated with unstable expansion of GAA trinucleotide repeats in the first intron of the FXN gene, which encodes the mitochondrial frataxin protein. Since FXN was shown to be involved in Friedreich's ataxia in the late 1990s, the consequence of frataxin loss of function has generated vigorous debate. Very early on we suggested a unifying hypothesis according to which frataxin deficiency leads to a vicious circle of faulty iron handling, impaired iron-sulphur cluster synthesis and increased oxygen radical production. However, data from cell and animal models now indicate that iron accumulation is an inconsistent and late event and that frataxin deficiency does not always impair the activity of iron-sulphur cluster-containing proteins. In contrast, frataxin deficiency appears to be consistently associated with increased sensitivity to reactive oxygen species as opposed to increased oxygen radical production. By compiling the findings of fundamental research and clinical observations we defend here the opinion that the very first consequence of frataxin depletion is indeed an abnormal oxidative status which initiates the pathogenic mechanism underlying Friedreich's ataxia

Pollen‐mediated gene flow from a commercial potato cultivar to the wild relative S. chacoense Bitter under experimental field conditions in Argentina

The common potato, Solanum tuberosum ssp. tuberosum (tbr, 2n = 4x = 48; 4EBN), has many closely related wild tuber‐bearing species. Around 28 to 35 of them spontaneously grow in Argentina overlapping, in some areas, with the crop and/or experimental transgenic potatoes. Although it is well proven that hybridization barriers in potatoes can be incomplete, information on gene flow between cultivated and wild germplasm is scarce. Thus, a gene flow field experiment with a circular array was set up in Balcarce, Argentina, in 2009, and evaluated over two seasons. The tetraploid tbr cultivar Huinkul MAG and one compatible cloned genotype of the related wild potato S. chacoense Bitter (chc, 2n = 2x = 24; 2EBN), which produced 2n eggs, were used, respectively, as pollen donor and receptor. Berries with hybrid seeds – as revealed by ploidy and RAPD profiles – were obtained in one season, at 30 m from the pollen donor. These results reinforce others previously obtained with the same pollen donor and a male sterile tbr cultivar in a similar array, pointing out to the need of increasing isolation distances in areas of overlap between cultivated and wild potato germplasm to prevent or minimize undesirable pollen‐mediated gene flow.EEA BalcarceFil: Capurro, Mauricio Antonio. Universidad Nacional de Mar del Plata. Facultad Ciencias Agrarias-Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Camadro, Elsa Lucila. Universidad Nacional de Mar del Plata. Facultad Ciencias Agrarias-Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Masuelli, Ricardo Williams. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria La Consulta; Argentin