Involvement of ethylene in the rooting of seedling shoot cultures of <Emphasis Type="Italic">Bixa orellana</Emphasis> L.

Using seedlings derived from the shoot apex of annatto (Bixa orellana L. cv. Bico-de-Pato) we observed the rooting frequency of B. orellana, the number and length of roots and the rate of ethylene production during 30 d in culture. The rhizogenesis response was affected by auxins (NAA or IBA) and by both the ethylene biosynthesis precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and the inhibitor 2-aminoethoxyvinylglycine (AVG). Auxin supplementation to the medium resulted in root induction, ethylene production, and an undesirable callusing in the epidermal and cortical tissues. Irrespective of the presence of auxins, supplementing the medium with ACC promoted ethylene biosynthesis and callusing, which resulted in increased cell proliferation mainly in the cortical and vascular tissues, while the epidermis was mostly unaltered. In both ACC and auxin-supplemented medium, increased ethylene production and callusing occurred, suggesting a synergistic effect between these two responses. ACC was capable of inducing adventitious root formation, but the roots produced had a wrinkled appearance when compared to normal roots. Conversely, AVG reduced ethylene production and callusing, while the epidermis, cortex, and inner tissues remained unaltered, regardless of the presence of auxins. AVG was beneficial in these aspects, although its application led to a reduction in the number of roots and in the average root length. In conclusion, it was not possible to establish a direct relation between ethylene and rooting, but we hypothesize that, under the experimental conditions described, ethylene may enhance tissue sensitivity to auxin. However, ethylene did not seem essential to the rhizogenesis process in annatto.     

Conservation biogeography of ecologically interacting species: the case of the Iberian lynx and the European rabbit

Aim To relate the recent Iberian lynx decline to changes in the distribution of the European rabbit after the haemorrhagic disease outbreak of 1989. As Iberian rabbits evolved in two geographically separated lineages, being the recent lynx range practically restricted to the southwestern lineage, we also test if differential range dynamics exists for these lineages, with the consequent implications for lynx conservation and reintroduction planning. Location The Iberian Peninsula. Methods We modelled environmental favourability for the lynx based on its distribution before 1989, and for the rabbit using distribution data collected primarily after 1989, and validated them using independent abundance data. We compared both models and combined them in a lynx occurrence forecast. We correlated the prevalence of southwestern rabbit lineage with the environmental favourability for the rabbit. Results The environmental lynx model correlated with past lynx abundance data, but did not reflect its recent strong range contraction. The rabbit model correlated with recent rabbit abundance, but was negatively correlated with the environmental model for the lynx. The combination of both models forecasted lynx occurrence in a few separated nuclei, which encompass all recent lynx records. The prevalence of rabbit's southwestern lineage correlated negatively with favourability for the rabbit. Main conclusions The region to which the lynx became confined before 1989 is currently less favourable for rabbits, whereas more favourable areas remain outside lynx reach. This differential favourability correlates with rabbit phylogeographical structure, suggesting that the southwestern lineage is facing more unfavourable conditions or is less resilient to recent diseases. The loss of concordance between lynx distribution and the whole rabbit phylogeographical structure has prevented lynx persistence in northeastern rabbit lineage areas, which should be considered in lynx reintroduction planning. Similar conservation problems could affect other ecologically interacting species whose distributions’ overlapping has sharply diminished.     

25S-Dihydrodracogenin: A new spirostan sapogenin from Semele androgyna

From stems and leaves of Semele androgyna L. the new steroid sapogenin 25S-dihydrodracogenin (Ia) has been isolated and its structure confirmed by conversion into the acetates of 25R-dihydrosansevierigenin (Id) and ruscogenin (If) and by partial hydrogenation of dracogenin.     

Phosphorylation-mediated stabilization of Bora in mitosis coordinates Plx1/Plk1 and Cdk1 oscillations

Cdk1 and Plk1/Plx1 activation leads to their inactivation through negative feedback loops. Cdk1 deactivates itself by activating the APC/C, consequently generating embryonic cell cycle oscillations. APC/C inhibition by the mitotic checkpoint in somatic cells and the cytostatic factor (CSF) in oocytes sustain the mitotic state. Plk1/Plx1 targets its co-activator Bora for degradation, but it remains unclear how embryonic oscillations in Plx1 activity are generated, and how Plk1/Plx1 activity is sustained during mitosis. We show that Plx1-mediated degradation of Bora in interphase generates oscillations in Plx1 activity and is essential for development. In CSF extracts, phosphorylation of Bora on the Cdk consensus site T52 blocks Bora degradation. Upon fertilization, Calcineurin dephosphorylates T52, triggering Plx1 oscillations. Similarly, we find that GFP-Bora is degraded when Plk1 activity spreads to somatic cell cytoplasm before mitosis. Interestingly, GFP–Bora degradation stops upon mitotic entry when Cdk1 activity is high. We hypothesize that Cdk1 controls Bora through an incoherent feedforward loop synchronizing the activities of mitotic kinases.     

On identifying common distribution patterns and their causal factors: a probabilistic method applied to pteridophytes in the Iberian Peninsula

Abstract. The aim of this quantitative biogeographical analysis is to identify the existence of specific groups of pteridophytes with significantly similar distribution patterns (chorotypes) in the Iberian Peninsula, as well as to infer the environmental factors that may explain such groupings. We have applied a classification method to the pteridophyte species and have then tested the significance of the resulting groups. This allows the distinction of groups of species that occur together more frequently than expected at random from those which are just a product of the cluster analysis. The majority of the 113 pteridophyte species in the Iberian Peninsula are not distributed independently from each other, but eighteen chorotypes exist that are common to various species and three chorotypes that consist of one species each. Five species are distributed independently of the other species, and so their distribution areas overlap and segregate from the others at random. With the aim of finding a relation between the chorotypes identified and the processes that determine them, we investigated the possible incidence of certain environmental factors on the chorotype distributions by means of logistic regression. Factors that appear most frequently as possible causes of the distribution of the chorotypes are the water availability, climatic stress, availability of environmental energy, and disturbances caused by floods. Resumen . El objetivo de este análisis biogeográfico cuantitativo es identificar la posible existencia de grupos de especies de pteridófitos con patrones de distribución significantivamente similares (corotipos) en la Peninsula Ibérica, así como analizar los factores ambientales que explican tales grupos. Hemos aplicado un método de clasificatión biogeográfica de especies y después hemos comprobado la significación de los grupos resultantes. Esto nos ha permitido distinguir los grupos de especies que se asocian con más frecuencia de lo esperado por azar de aquellos grupos que se deben únicamente al análisis de agrupación. La mayoría de las 113 especies de pteridófitos en la Península Ibérica no se distribuyen independientemente unas de otras, sino que existen 18 corotipos que son comunes a varias especies y tres que están formados por una sola especie. Cinco especies se distribuyen independientemente de las restantes, y por tanto, sus áreas de distribución se solapan y se segregan con las demás al azar. Con objeto de encontrar una relación entre los corotipos identificados en el presente trabajo y los procesos que los determinan, investigamos por medio de regresiones logísticas la posible incidencia de ciertos factores ambientales sobre las distribuciones de los corotipos. Los factores que han aparecido más frecuentemente como posibles causas de las distribuciones de los corotipos son la disponibilidad de agua, el estrés climático, la energía ambiental disponible y los disturbios causados por las inundaciones.