Membrane permeabilisation and antimycoplasmic activity of the 18-residue peptaibols, trichorzins PA

AbstractThe membrane permeabilisation properties of six linear natural 18-residue peptaibols, termed trichorzins PA, have been assessed on liposomes and on mollicutes (trivial name, mycoplasmas), a class of parasitic bacteria characterized by a small genome, the lack of a cell wall, a minute cell size, and the incorporation in their plasma membrane of exogenously supplied cholesterol. The trichorzins PA used in this study (PA II, PA IV–VI, PA VIII, and PA IX) differ between them by amino acid or amino alcohol substitutions at positions 4, 7, and 18, and form slightly amphipathic α-helices. They proved bactericidal for mollicutes belonging to the genera Acholeplasma, Mycoplasma, and Spiroplasma, with minimal inhibitory concentrations (3.12≤MICs≤50 μM) generally 2 to 4 fold higher than those of alamethicin F50, a related 20-residue peptide (1.56≤MICs≤12.5 μM). Spiroplasma cells were apparently not protected by the presence of spiralin on their surface. The activities of the six trichorzins PA were not influenced by their sequence variations and no synergistic effect was observed. Consistent with the marginal effect of cholesterol on the incorporation of the trichorzins PA into liposome bilayers, the antibiotic activity was independent of the amount of cholesterol in the membranes of the different mollicutes. The trichorzins PA and alamethicin inhibited the motility of Spiroplasma melliferum, the helical cells being deformed and split into coccoid forms. Membrane potential measurements in Acholeplasma laidlawii and S. melliferum showed that trichorzin PA V and alamethicin F50 very efficiently depolarized the plasma membrane of mollicutes. This was consistent with fluorescence and 23Na NMR measurements on liposomes that revealed the permeabilisation of the lipid bilayer and the nonselective ionophoric activity of the trichorzins PA. These data suggest that the bactericidal activity exhibited by the trichorzins PA on mollicutes is due to the permeabilisation of the plasma membrane

Ma Orthologous Genes in Prunus spp. Shed Light on a Noteworthy NBS-LRR Cluster Conferring Differential Resistance to Root-Knot Nematodes

Root-knot nematodes (RKNs) are considerable polyphagous pests that severely challenge plants worldwide and especially perennials. The specific genetic resistance of plants mainly relies on the NBS-LRR genes that are pivotal factors for pathogens control. In Prunus spp., the Ma plum and RMja almond genes possess different spectra for resistance to RKNs. While previous works based on the Ma gene allowed to clone it and to decipher its peculiar TIR-NBS-LRR (TNL) structure, we only knew that the RMja gene mapped on the same chromosome as Ma. We carried out a high-resolution mapping using an almond segregating F2 progeny of 1448 seedlings from resistant (R) and susceptible (S) parental accessions, to locate precisely RMja on the peach genome, the reference sequence for Prunus species. We showed that the RMja gene maps in the Ma resistance cluster and that the Ma ortholog is the best candidate for RMja. This co-localization is a crucial step that opens the way to unravel the molecular determinants involved in the resistance to RKNs. Then we sequenced both almond parental NGS genomes and aligned them onto the RKN susceptible reference peach genome. We produced a BAC library of the R parental accession and, from two overlapping BAC clones, we obtained a 336-kb sequence encompassing the RMja candidate region. Thus, we could benefit from three Ma orthologous regions to investigate their sequence polymorphism, respectively, within plum (complete R spectrum), almond (incomplete R spectrum) and peach (null R spectrum). We showed that the Ma TNL cluster has evolved orthologs with a unique conserved structure comprised of five repeated post-LRR (PL) domains, which contain most polymorphism. In addition to support the Ma and RMja orthologous relationship, our results suggest that the polymorphism contained in the PL sequences might underlie differential resistance interactions with RKNs and an original immune mechanism in woody perennials. Besides, our study illustrates how PL exon duplications and losses shape TNL structure and give rise to atypical PL domain repeats of yet unknown role

Biomphalysin, a new β pore-forming toxin involved in Biomphalaria glabrata immune defense against Schistosoma mansoni.

International audienceAerolysins are virulence factors belonging to the β pore-forming toxin (β-PFT) superfamily that are abundantly distributed in bacteria. More rarely, β-PFTs have been described in eukaryotic organisms. Recently, we identified a putative cytolytic protein in the snail, Biomphalaria glabrata, whose primary structural features suggest that it could belong to this β-PFT superfamily. In the present paper, we report the molecular cloning and functional characterization of this protein, which we call Biomphalysin, and demonstrate that it is indeed a new eukaryotic β-PFT. We show that, despite weak sequence similarities with aerolysins, Biomphalysin shares a common architecture with proteins belonging to this superfamily. A phylogenetic approach revealed that the gene encoding Biomphalysin could have resulted from horizontal transfer. Its expression is restricted to immune-competent cells and is not induced by parasite challenge. Recombinant Biomphalysin showed hemolytic activity that was greatly enhanced by the plasma compartment of B. glabrata. We further demonstrated that Biomphalysin with plasma is highly toxic toward Schistosoma mansoni sporocysts. Using in vitro binding assays in conjunction with Western blot and immunocytochemistry analyses, we also showed that Biomphalysin binds to parasite membranes. Finally, we showed that, in contrast to what has been reported for most other members of the family, lytic activity of Biomphalysin is not dependent on proteolytic processing. These results provide the first functional description of a mollusk immune effector protein involved in killing S. mansoni

Pedigree analysis of 220 almond genotypes reveals two world mainstream breeding lines based on only three different cultivars

Loss of genetic variability is an increasing challenge in tree breeding programs due to the repeated use of a reduced number of founder genotypes. However, in almond, little is known about the genetic variability in current breeding stocks, although several cases of inbreeding depression have been reported. To gain insights into the genetic structure in modern breeding programs worldwide, marker-verified pedigree data of 220 almond cultivars and breeding selections were analyzed. Inbreeding coefficients, pairwise relatedness, and genetic contribution were calculated for these genotypes. The results reveal two mainstream breeding lines based on three cultivars: “Tuono”, “Cristomorto”, and “Nonpareil”. Descendants from “Tuono” or “Cristomorto” number 76 (sharing 34 descendants), while “Nonpareil” has 71 descendants. The mean inbreeding coefficient of the analyzed genotypes was 0.041, with 14 genotypes presenting a high inbreeding coefficient, over 0.250. Breeding programs from France, the USA, and Spain showed inbreeding coefficients of 0.075, 0.070, and 0.037, respectively. According to their genetic contribution, modern cultivars from Israel, France, the USA, Spain, and Australia trace back to a maximum of six main founding genotypes. Among the group of 65 genotypes carrying the Sf allele for self-compatibility, the mean relatedness coefficient was 0.125, with “Tuono” as the main founding genotype (24.7% of total genetic contribution). The results broaden our understanding about the tendencies followed in almond breeding over the last 50 years and will have a large impact into breeding decision-making process worldwide. Increasing current genetic variability is required in almond breeding programs to assure genetic gain and continuing breeding progress.info:eu-repo/semantics/publishedVersio

Transposons played a major role in the diversification between the closely related almond and peach genomes: Results from the almond genome sequence

We sequenced the genome of the highly heterozygous almond Prunus dulcis cv. Texas combining short and long‐read sequencing. We obtained a genome assembly totaling 227.6 Mb of the estimated 238 Mb almond genome size, of which 91% is anchored to eight pseudomolecules corresponding to its haploid chromosome complement, and annotated 27,969 protein‐coding genes and 6,747 non‐coding transcripts. By phylogenomic comparison with the genomes of 16 additional close and distant species we estimated that almond and peach (P. persica) diverged around 5.88 Mya. These two genomes are highly syntenic and show a high degree of sequence conservation (20 nucleotide substitutions/kb). However, they also exhibit a high number of presence/absence variants, many attributable to the movement of transposable elements (TEs). TEs have generated an important number of presence/absence variants between almond and peach, and we show that the recent history of TE movement seems markedly different between them. TEs may also be at the origin of important phenotypic differences between both species, and in particular, for the sweet kernel phenotype, a key agronomic and domestication character for almond. Here we show that in sweet almond cultivars, highly methylated TE insertions surround a gene involved in the biosynthesis of amygdalin, whose reduced expression has been correlated with the sweet almond phenotype. Altogether, our results suggest a key role of TEs in the recent history and diversification of almond and its close relative peach.info:eu-repo/semantics/publishedVersio

Simulation Modifies Prehension: Evidence for a Conjoined Representation of the Graspable Features of an Object and the Action of Grasping It

Movement formulas, engrams, kinesthetic images and internal models of the body in action are notions derived mostly from clinical observations of brain-damaged subjects. They also suggest that the prehensile geometry of an object is integrated in the neural circuits and includes the object's graspable characteristics as well as its semantic properties. In order to determine whether there is a conjoined representation of the graspable characteristics of an object in relation to the actual grasping, it is necessary to separate the graspable (low-level) from the semantic (high-level) properties of the object. Right-handed subjects were asked to grasp and lift a smooth 300-g cylinder with one hand, before and after judging the level of difficulty of a “grasping for pouring” action, involving a smaller cylinder and using the opposite hand. The results showed that simulated grasps with the right hand exert a direct influence on actual motor acts with the left hand. These observations add to the evidence that there is a conjoined representation of the graspable characteristics of the object and the biomechanical constraints of the arm

Estrategias lúdicas para el desarrollo del razonamiento lógico matemático.

"Los juegos durante cientos de generaciones han constituido la base de educación del hombre espontanea, permitiendo la transmisión de las normas de convivencias social, mejorar las tradiciones y el desarrollo de la capacidad creadora. Esto propiciara la camarería, el interés, el gusto por las matemáticas ya que el juego estimula y fomenta a que el estudiante sea más creativo. Luego de un arduo trabajo de investigación en la escuela de niña Nº 13 Manuela Cañizares hemos detectado que una gran cantidad de alumnas tienen problema en el desarrollo del razonamiento lógico en el área de matemática, lo cual nos vimos en la necesidad de buscar soluciones. Llegando a la conclusión que si aplicamos las estrategias lúdicas dejamos a un lado la educación tradicionalista con eso rompemos el esquema y formamos un nuevo paradigma. Es importante, que la elección de las estrategias lúdicas dejamos a un lado la educación tradicionalista con eso rompemos el esquema y formamos un nuevo paradigma. Es importante, que la elección de las estrategias lúdicas siga bajo criterios realista y de forma equilibrada, en el sentido de que sea positiva no solo para las alumnas que en un momento u otro experimenta dificultades para aprender, sino para la globalidad del grupo de clase. En nuestro proyecto se habla de elegir diversas alternativas como el de enseñar a los estudiantes a tomar decisiones ante problema que puedan surgir en su vida. Garantizar la posibilidad de la adquisición de una experiencia práctica del razonamiento, ya que el proyecto despierte el interés hacia la asignatura permitiendo comprobar el nivel de conocimiento alcanzado. Por medio de la guía elaborada por los investigadores, nos permitirá ayudar a las estudiantes a desarrollar habilidades, consolidar sus conocimientos y fortalecer los valores. Ya que el juego didáctico permitirá el perfeccionamiento de las capacidades de los estudiantes en el desarrollo de la capacidad de análisis. Por eso es necesario que se aplique las estrategias lúdicas para el éxito académico del educando.

Pedigree analysis of 220 almond genotypes reveals two world mainstream breeding lines based on only three different cultivars

[ES]: Reducir la pérdida de variabilidad genética es un reto en los programas de mejora debido al repetido uso de un escaso número de genotipos. Para estudiar la variabilidad genética del almendro en su mejora a nivel mundial se utilizaron datos genealógicos de 222 variedades y selecciones provenientes de Argentina, Australia, Francia, Grecia, Israel, Italia, Rusia, España y EE. UU. Se calculó la consanguinidad, las relaciones por parejas y la contribución genética para todos los genotipos. Los resultados señalan dos principales líneas de mejora basadas en tres cultivares ‘Tuono’–‘Cristomorto’ y ‘Nonpareil’. Existen 75 descendientes directos (compartiendo 30) de ‘Tuono’ o ‘Cristomorto’ mientras que ‘Nonpareil’ tiene 72 descendientes directos. El coeficiente medio de consanguinidad de los genotipos analizados fue 0,036, con 13 presentando una elevada consanguinidad. Los programas de mejora de EE. UU. (0,06), Francia (0,05) y España (0,03) mostraron consanguinidad. De acuerdo con su contribución genética, las variedades modernas de Israel, Francia, EE. UU., España y Australia, se basan en seis, cinco, cuatro, cuatro y dos genotipos fundadores principales respectivamente. Entre el grupo de 65 genotipos con el alelo Sf de autocompatibilidad, el coeficiente medio de relación fue de 0,133, con ‘Tuono’ como principal fundador (23,75% de la contribución genética total).[EN]: Loss of genetic variability is a challenge increasing when breeding due to the repeated use of a reduced number of founders. Pedigree data of 222 almond cultivars and selections were used to study worldwide genetic variability in modern programs from Argentina, Australia, France, Greece, Israel, Italy, Russia, Spain and USA. Inbreeding coefficients, pairwise relatedness and genetic contribution were calculated. The results reveal two mainstream breeding lines based in three cultivars: ‘Tuono’–‘Cristomorto’ and ‘Nonpareil’. Direct descendants from ‘Tuono’ or ‘Cristomorto’ account to 75 (sharing 30 descendants), while ‘Nonpareil’ has 72 direct descendants. The mean inbreeding coefficient of the analyzed genotypes was 0.036, with 13 genotypes presenting a high inbreeding coefficient. Breeding programs from USA (0.06), France (0.05) and Spain (0.03) showed inbreeding. According to their genetic contribution, modern cultivars from Israel, France, USA, Spain and Australia, trace back to six, five, four, four and two main founders respectively. Among the group of 65 genotypes with the Sf allele for self–compatibility, the mean relatedness coefficient was 0.133, with ‘Tuono’ as main founder (23.75% of total genetic contribution).Peer reviewe