Systematic relevance of seed coat anatomy in the European heathers (Ericeae, Ericaceae)

The anatomy of the seed coat of the European species of tribe Ericeae (Calluna, Daboecia and Erica) of the Ericaceae family was studied, and the taxonomic importance of their characters was analyzed. The seed coat is mostly formed by a one-cell layer with thick, pitted inner walls and thin outer walls that collapse at maturity over the inner walls. The cell junctions are either raised with anticlinal walls up to four times the height of the periclinal walls or are not raised with similar values for the height of both the anticlinal and periclinal walls. Three main cell junction types were found and described. The thickness of the inner walls is variable, but there is a large overlap among the results for different species. Calluna vulgaris is the only species with no pits, and E. multiflora has a pitted pattern on its inner walls, which is distinctive from the rest of the species. Our main results agree with the external seed morphology, and valuable new data were obtained for certain groups such as the E. cinerea-E. terminalis or the E. scoparia complex. The similarities that are found in seed coat characters are not in accordance with the classical taxonomic delimitation of infrageneric groups within Erica.     

Production of aborted pollen in marsh species of Chenopodiaceae: evidence of partial male sterility in Suadeaea and Salsoleae species

The main objective of this study is to establish the level of pollen abortion prior to its release from the anther in species of Chenopodiaceae in marsh habitats and to compare this level among the taxons, locations and positions of the flowers in the dichasium and the relative positions of the anthers. We established the level of nonfunctional pollen formation in 39 samples belonging to 10 species, using lactophenol cotton blue staining. Aborted pollen grains were found to be significantly smaller than normal ones. The results revealed differences in the percentage of normal grains among different species and tribes studied: Atripliceae (56.1 ± 27.1%), Salicornieae (80.36 ± 16.52%), Suaedeae (54.7 ± 31.2%) and Salsoleae (32.5 ± 25.7%). In some species there were significant differences among the populations studied, but in species of Saliconieae we found no differences either between different positions in the dicasia or in the anther. In the tribes Suaedeae and Salsoleae, we postulate the existence of a system that maintains different levels of partial male sterility among individuals in the populations, which would reduce the autogamous fruit set rate and favor the cross-pollination rates of sterile male individuals. We base this on high intrapopulation variability at those levels, on the constancy with which they are presented in the different populations studied, and on the lack of interannual differences.     

The effect of methyl jasmonate on triterpene and sterol metabolisms of Centella asiatica, Ruscus aculeatus and Galphimia glauca cultured plants

Considering that exogenously applied methyl jasmonate can enhance secondary metabolite production in a variety of plant species and that 2,3-oxidosqualene is a common precursor of triterpenes and sterols in plants, we have studied Centella asiatica and Galphimia glauca (both synthesizing triterpenoid secondary compounds) and Ruscus aculeatus (which synthesizes steroidal secondary compounds) for their growth rate and content of free sterols and respective secondary compounds, after culturing with or without 100 microM methyl jasmonate. Our results show that elicited plantlets of G. glauca and to a higher degree C. asiatica (up to 152-times more) increased their content of triterpenoids directly synthesized from 2,3-oxidosqualene (ursane saponins and nor-seco-friedelane galphimines, respectively) at the same time as growth decreased. In contrast, the free sterol content of C. asiatica decreased notably, and remained practically unaltered in G. glauca. However, in the case of R. aculeatus, which synthesizes steroidal saponins (mainly spirostane type) indirectly from 2,3-oxidosqualene after the latter is converted to the plant phytosterol-precursor cycloartenol, while the growth rate and free sterol content clearly decreased, the spirostane saponine content was virtually unchanged (aerial part) or somewhat lower (roots) in presence of the same elicitor concentration. Our results suggest that while methyl jasmonate may be used as an inducer of enzymes involved in the triterpenoid synthesis downstream from 2,3-oxidosqualene in both C. asiatica and G. glauca plantlets, in those of C. asiatica and R. aculeatus it inhibited the enzymes involved in sterol synthesis downstream from cycloartenol.     

Induction of gentisic acid 5-O-beta-D-xylopyranoside in tomato and cucumber plants infected by different pathogens

Tomato plants infected with the citrus exocortis viroid exhibited strongly elevated levels of a compound identified as 2,5-dihydroxybenzoic acid (gentisic acid, GA) 5-O-beta-D-xylopyranoside. The compound accumulated early in leaves expressing mild symptoms from both citrus exocortis viroid-infected tomato, and prunus necrotic ringspot virus-infected cucumber plants, and progressively accumulated concomitant with symptom development. The work presented here demonstrates that GA, mainly associated with systemic infections in compatible plant-pathogen interactions [Bellés, J.M., Garro, R., Fayos, J., Navarro, P., Primo, J., Conejero, V., 1999. Gentisic acid as a pathogen-inducible signal, additional to salicylic acid for activation of plant defenses in tomato. Mol. Plant-Microbe Interact. 12, 227-235], is conjugated to xylose. Notably, this result contrasts with those previously found in other plant-pathogen interactions in which phenolics analogues of GA as benzoic or salicylic acids, are conjugated to glucose.     

A new method to analyze boar sperm DNA fragmentation under bright-field or fluorescence microscopy

We present a new, rapid and simple method to study DNA Fragmentation Index (DFI) in sperm samples from boar under bright-field and fluorescence microscopy. Discrimination of sperm cells containing fragmented DNA relies on the extreme peripheral diffusion of their chromatin fragments, whereas those sperm nuclei without DNA fragmentation do not disperse or show very restricted spreading of DNA loops close to the flagellum. The basic methodology provided in the commercial kit Sperm-Sus-Halomax allows, in addition to a direct estimation of DFI in a sperm sample under bright field microscopy, a direct visualization of DNA breaks by incorporation of labelled nucleotides using the DNA polymerase I following the in situ nick translation assay (ISNT methodology not provided in the kit). An external control using DBD-FISH (DNA breakage detection-fluorescence in situ hybridization) on human and boar sperm samples was used in this experiment. The results obtained show (i) low levels of background DNA fragmentation (from 0.7 to 10%), (ii) no significant differences for DFI after the application of Sperm-Sus-Halomax and ISNT, with a tendency to be underestimated after using DBD-FISH and (iii) a characteristic chromatin organization in boar sperm nucleus, with a particular response to chromatin loop relaxation and preferential DNA labelling by ISNT at the proximal nuclear area, close to the flagellum. This methodology allows the routine assessment of boar sperm samples for DFI, as well as basic and clinical research on this relevant topic in any laboratory of semen analysis.     

Event-driven time-optimal control for a class of discontinuous bioreactors

Discontinuous bioreactors may be further optimized for processing inhibitory substrates using a convenient fed-batch mode. To do so the filling rate must be controlled in such a way as to push the reaction rate to its maximum value, by increasing the substrate concentration just up to the point where inhibition begins. However, an exact optimal controller requires measuring several variables (e.g., substrate concentrations in the feed and in the tank) and also good model knowledge (e.g., yield and kinetic parameters), requirements rarely satisfied in real applications. An environmentally important case, that exemplifies all these handicaps, is toxicant wastewater treatment. There the lack of online practical pollutant sensors may allow unforeseen high shock loads to be fed to the bioreactor, causing biomass inhibition that slows down the treatment process and, in extreme cases, even renders the biological process useless. In this work an event-driven time-optimal control (ED-TOC) is proposed to circumvent these limitations. We show how to detect a "there is inhibition" event by using some computable function of the available measurements. This event drives the ED-TOC to stop the filling. Later, by detecting the symmetric event, "there is no inhibition," the ED-TOC may restart the filling. A fill-react cycling then maintains the process safely hovering near its maximum reaction rate, allowing a robust and practically time-optimal operation of the bioreactor. An experimental study case of a wastewater treatment process application is presented. There the dissolved oxygen concentration was used to detect the events needed to drive the controller.     

Local origin and diversification among Lampornis hummingbirds: a Mesoamerican taxon

The huge biodiversity found in Mesoamerica is often explained by its geographic situation as a natural bridge between two large biogeographic regions. Often overlooked, however, are the high levels of speciation and diversification in the area. Here we assess the phylogenetic relationships within a Mesoamerican group of hummingbirds (Lampornis). We sequenced both mtDNA (1,143 bp of cyt b and 727 bp of ND5) and nuclear genes (505 bp of AK-5 intron and 567 bp of c-mos) for each of the seven recognised species and outgroups. We find two or three clades of similar age within this genus: L. clemenciae and L. amethystinus (singly or as each other's sister taxa) and a Central American clade. This Central-American clade presents a clear bipartition between northern (L. viridipallens and L. sybillae) and southern Mesoamerica, which is shared with many other Mesoamerican organisms. Our analyses suggest that L. hemileucus does not belong in the genus Lampornis. While we refrain to apply a time-scale to our data because of the lack of an appropriate calibration, our results indicate that the genus Lampornis predates the uprising of the Panama land-bridge, and that diversification among the isthmian species (L. castaneoventris and L. calolaema) is a very recent event. Our results strongly suggest a local Mesoamerican origin for this genus.     

Preliminary methylation analysis of prothymosin α genomic sequences

Prothymosin α is a mammalian nuclear protein involved in cell proliferation and differentiation. Here, we carried out the first study of the methylation status of ProTα genomic sequences in cell lines during differentiation as well as in tumoral tissues. We found that there is hypermethylation in all cell lines analyzed with a pattern that is characteristic of each cell type revealing specific genomic reorganizations. The decrease of ProTα mRNA during differentiation was not accompanied by changes in the methylation status. Remarkably, we found that there is hypomethylation in gastrointestinal tumors when compared with the peritumoral tissue. The biological implications of these findings are discussed.