Noves associacions rupicoles dels Pirineus catalans

La vegetado ruplcola dels Pirineus inclou, com ja se sap, una gran proporció d'espécies particulars, tant per la seva forta adequació a 1'ambient rupestre com pel seu acusat grau d'endemisme; aixó fa que les comunitats vegetáis siguin en general molt ben caracteritzades i d'área ben delimitada. En aquesta nota descrivim una nova associació, propia de les roques calcináis assolellades, que tot i no posseint caracterís tiques exclusives, resulta perfectament definida dins el sector oriental de la serralada. També proposem una nova comunitat del Centrantho-Parietarion, exclusiva dels hábits rupestres ruderalitzats.

Consequences of lineage-specific gene loss on functional evolution of surviving paralogs: ALDH1A and retinoic acid signaling in vertebrate genomes

Genome duplications increase genetic diversity and may facilitate the evolution of gene subfunctions. Little attention, however, has focused on the evolutionary impact of lineage-specific gene loss. Here, we show that identifying lineage-specific gene loss after genome duplication is important for understanding the evolution of gene subfunctions in surviving paralogs and for improving functional connectivity among human and model organism genomes. We examine the general principles of gene loss following duplication, coupled with expression analysis of the retinaldehyde dehydrogenase Aldh1a gene family during retinoic acid signaling in eye development as a case study. Humans have three ALDH1A genes, but teleosts have just one or two. We used comparative genomics and conserved syntenies to identify loss of ohnologs (paralogs derived from genome duplication) and to clarify uncertain phylogenies. Analysis showed that Aldh1a1 and Aldh1a2 form a clade that is sister to Aldh1a3-related genes. Genome comparisons showed secondarily loss of aldh1a1 in teleosts, revealing that Aldh1a1 is not a tetrapod innovation and that aldh1a3 was recently lost in medaka, making it the first known vertebrate with a single aldh1a gene. Interestingly, results revealed asymmetric distribution of surviving ohnologs between co-orthologous teleost chromosome segments, suggesting that local genome architecture can influence ohnolog survival. We propose a model that reconstructs the chromosomal history of the Aldh1a family in the ancestral vertebrate genome, coupled with the evolution of gene functions in surviving Aldh1a ohnologs after R1, R2, and R3 genome duplications. Results provide evidence for early subfunctionalization and late subfunction-partitioning and suggest a mechanistic model based on altered regulation leading to heterochronic gene expression to explain the acquisition or modification of subfunctions by surviving ohnologs that preserve unaltered ancestral developmental programs in the face of gene loss.

Analysis of a Plant Complex Resistance Gene Locus Underlying Immune-Related Hybrid Incompatibility and Its Occurrence in Nature

Mechanisms underlying speciation in plants include detrimental (incompatible) genetic interactions between parental alleles that incur a fitness cost in hybrids. We reported on recessive hybrid incompatibility between an Arabidopsis thaliana strain from Poland, Landsberg erecta (Ler), and many Central Asian A. thaliana strains. The incompatible interaction is determined by a polymorphic cluster of Toll/interleukin-1 receptor-nucleotide binding-leucine rich repeat (TNL) RPP1 (Recognition of Peronospora parasitica1)-like genes in Ler and alleles of the receptor-like kinase Strubbelig Receptor Family 3 (SRF3) in Central Asian strains Kas-2 or Kond, causing temperature-dependent autoimmunity and loss of growth and reproductive fitness. Here, we genetically dissected the RPP1-like Ler locus to determine contributions of individual RPP1-like Ler (R1R8) genes to the incompatibility. In a neutral background, expression of most RPP1-like Ler genes, except R3, has no effect on growth or pathogen resistance. Incompatibility involves increased R3 expression and engineered R3 overexpression in a neutral background induces dwarfism and sterility. However, no individual RPP1-like Ler gene is sufficient for incompatibility between Ler and Kas-2 or Kond, suggesting that co-action of at least two RPP1-like members underlies this epistatic interaction. We find that the RPP1-like Ler haplotype is frequent and occurs with other Ler RPP1-like alleles in a local population in Gorzów Wielkopolski (Poland). Only Gorzów individuals carrying the RPP1-like Ler haplotype are incompatible with Kas-2 and Kond, whereas other RPP1-like alleles in the population are compatible. Therefore, the RPP1-like Ler haplotype has been maintained in genetically different individuals at a single site, allowing exploration of forces shaping the evolution of RPP1-like genes at local and regional population scales.

Ximpanzés maltractadors de femelles

De vegades els ximpanzés es comporten de manera agressiva cap als seus congèneres. Fa temps que s'estudien les batusses que de tant en tant mantenen els mascles de diferents grups, i se sap que en alguns casos diversos mascles s'han associat per assassinar un company que s'hagi mostrat especialment dominant. Joseph T. Feldblum i els seus col·laboradors, en diverses universitats i centres de recerca dels EUA, han analitzat un comportament agressiu molt específic que manifesten alguns ximpanzés mascle cap a les femelles del seu grup. Els resultats, publicats a Current Biology, indiquen que, paradoxalment, aquests mascles tenen més descendents que els no agressius, perquè les femelles que s'han aparellat amb ells rebutgen posteriors còpules amb altres mascles.

Intel·lecte plaent

Una de les maneres com els instints afavoreixen la seva satisfacció és associant-la a plaer. Tothom sap que quan realitzem les funcions vitals, com per exemple quan mengem, bevem o practiquem el sexe, experimentem un plaer físic associat als sentits.Quan un individu sent plaer, el seu cervell indueix la producció d'hormones com l'endorfina, l'oxitocina i la serotonina,que causen un estat general de benestar. Tanmateix, el plaer físic, que habitualment ha estat considerat com el més baix dels plaers, no n'és pas l'única forma. Una altra forma de plaer és l'emocional, que ve de la satisfacció de les necessitats d'afecte i admiració,i que es relaciona directament amb la capacitat social humana [...].