A Deviation from the Bipolar-Tetrapolar Mating Paradigm in an Early Diverged Basidiomycete

In fungi, sexual identity is determined by specialized genomic regions called MAT loci which are the equivalent to sex chromosomes in some animals and plants. Usually, only two sexes or mating types exist, which are determined by two alternate sets of genes (or alleles) at the MAT locus (bipolar system). However, in the phylum Basidiomycota, a unique tetrapolar system emerged in which four different mating types are generated per meiosis. This occurs because two functionally distinct molecular recognition systems, each encoded by one MAT region, constrain the selection of sexual partners. Heterozygosity at both MAT regions is a pre-requisite for mating in both bipolar and tetrapolar basidiomycetes. Tetrapolar mating behaviour results from the absence of genetic linkage between the two regions bringing forth up to thousands of mating types. The subphylum Pucciniomycotina, an early diverged lineage of basidiomycetes encompassing important plant pathogens such as the rusts and saprobes like Rhodosporidium and Sporidiobolus, has been so far poorly explored concerning the content and organization of MAT loci. Here we show that the red yeast Sporidiobolus salmonicolor has a mating system unlike any previously described because occasional disruptions of the genetic cohesion of the bipolar MAT locus originate new mating types. We confirmed that mating is normally bipolar and that heterozygosity at both MAT regions is required for mating. However, a laboratory cross showed that meiotic recombination may occur within the bipolar MAT locus, explaining tetrapolar features like increased allele number and evolution rates of some MAT genes. This pseudo-bipolar system deviates from the classical bipolar–tetrapolar paradigm and, to our knowledge, has never been observed before. We propose a model for MAT evolution in the Basidiomycota in which the pseudo-bipolar system may represent a hitherto unforeseen gradual form of transition from an ancestral tetrapolar system to bipolarity

Idéologie(s) et roman pour la jeunesse au xxie siècle

Né juste après la Révolution française pour désigner la science des idées, le mot « idéologie » s'est dévalué au cours du xxe siècle et il suscite aujourd'hui le débat à plusieurs titres, au premier chef lorsqu'il s'agit de le définir. Dans le domaine du livre de jeunesse, la conjonction entre idéologie, instruction publique et éducation s'inscrit au cœur des enjeux d'une littérature adressée et sous surveillance que l'auteur, l'éditeur, le médiateur ont toujours cherché à encadrer à des fins éducatives. C'est dans ce champ particulier que l'on se propose d'affronter la complexité d'une notion « labile et fourbe », d'après Bruno Blanckeman, pour en circonvenir les manifestations et les effets dans les entreprises romanesques de l'extrême contemporain. Faute de définition stable et univoque, sans doute convient-il ici d'embrasser la notion au pluriel et de concevoir les idéologies comme des « systèmes fixes de valeurs ordonnancées » qui trouvent un terrain de prédilection dans le roman, lui-même genre pluriel, « archi-genre » qui orchestre une polyphonie de discours et s'accommode de toutes les hybridités. En observant certains de ses sous-genres - roman-miroir, roman de fantasy, roman dystopique, roman post-colonial - les différents contributeurs sont conduits à se demander dans quelle mesure le roman contemporain pour la jeunesse met en œuvre une « poétique des valeurs » et s'il rend possible l'émergence de ces « fictions critiques » que Dominique Viart définit comme des textes où « le discours met en crise la pensée ». Les articles réunis ici interrogent dans les romans pour la jeunesse l'approche, souvent paradoxale, des grandes questions soulevées par les évolutions du monde contemporain. Au moment où l'actualité concernant l'école en France se cristallise à nouveau sur le sujet de l'enseignement de la morale, la réflexion s'attache notamment aux corpus romanesques prescrits par l'institution scolaire et à leur enseignement

Processing quality of potato tubers produced during autumn and spring and stored at different temperatures Qualidade de processamento de tubérculos de batata produzidos no outono e na primavera e armazenados em diferentes temperaturas

The objective of this work was to access processing quality of potato clones (Solanum tuberosum) Asterix, SMINIA793101-3, and Missaukee cultivated during spring and autumn growing seasons and stored at 4, 8, 12, or 25ºC. Clones grown in spring had shorter dormancy than clones grown in autumn. Potato tubers grown in spring and autumn and stored at 4ºC, as well as tubers grown in autumn and stored at 8ºC had no sprouting for six months. Among clones grown in autumn, the longest dormancy period during storage at 12ºC was observed in the clone SMINIA793101-3, and at 25ºC was in the clone Asterix. In potato tubers grown in spring, the longest dormancy period during storage at 8ºC was observed in the clones SMINIA793101-3 and Missaukee, at 12ºC was in the clone SMINIA793101-3, and at 25ºC was in the clones Asterix and Missaukee. Potato tubers grown in spring had higher dry matter, starch content, and respiration rates, and lower reducing sugar, and total polyphenol content. The only exception was the Missaukee that had similar dry matter content in both growing seasons. In general, storage at 4ºC and 8ºC were more effective in reducing respiration rates and maintaining higher dry mater content of potato tubers. Chip darkening, reducing sugars, and total polyphenol content increased during storage of potato tubers. Darker chip color, higher reducing sugars and polyphenol content were obtained during storage at temperatures of 4ºC and 8ºC. These results suggest that the best storage temperature depends on genotype, tuber physiological age, and growing conditions.<br>O objetivo deste trabalho foi determinar a qualidade de processamento dos clones de batata (Solanum tuberosum) Asterix, SMINIA793101-3, e Missaukee cultivados durante outono e primavera e armazenados a 4, 8, 12, ou 25ºC. Clones produzidos na primavera tiveram menor período de dormência que clones produzidos no outono. Tubérculos produzidos na primavera e outono e armazenados a 4ºC, assim como tubérculos produzidos no outono e armazenados a 8ºC não apresentaram brotação por seis meses. Entre os clones cultivados no outono, o maior período de dormência durante o armazenamento a 12ºC foi observado no clone SMINIA793101-3, e a 25ºC foi no clone Asterix. Em tubérculos produzidos na primavera, o maior período de dormência durante o armazenamento a 8ºC foi observado nos clones SMINIA793101-3 e Missaukee, a 12ºC foi no clone SMINIA793101-3, e a 25ºC foi nos clones Asterix e Missaukee. Tubérculos produzidos na primavera continham maiores teores de massa seca e amido, maiores taxas respiratórias, e menores concentrações de açucares redutores e polifenóis totais. A única excessão foi o clone Missaukee que apresentou teores de matéria seca similares em ambas as épocas de cultivo. De modo geral, as temperaturas de armazenamento, 4ºC e 8ºC, foram mais efetivas na redução da respiração e na prevenção da redução dos teores de matéria seca de tubérculos. Escurecimento de chip, concentração de açúcares redutores e polifenóis totais aumentaram durante o armazenamento dos tubérculos. Os maiores valores de escurecimento de chip, açúcares redutores e polifenóis totais foram obtidos com o armazenamento a 4ºC e 8ºC. Os resultados sugerem que a melhor temperatura de armazenamento depende do genótipo, idade fisiológica do tubérculo, e condições de cultivo