RESUMEN
Discovery of sexual development in the ascomycete Trichoderma reesei (Hypocrea jecorina) as well as detection of a novel class of peptide pheromone precursors in this fungus indicates promising insights into its physiology and lifestyle. Here we investigated the role of the two pheromone receptors HPR1 and HPR2 in the H. jecorina pheromone-system. We found that these pheromone receptors show an unexpectedly high genetic variability among H. jecorina strains. HPR1 and HPR2 confer female fertility in their cognate mating types (MAT1-1 or MAT1-2, respectively) and mediate induction of fruiting body development. One compatible pheromone precursor-pheromone receptor pair (hpr1-hpp1 or hpr2-ppg1) in mating partners was sufficient for sexual development. Additionally, pheromone receptors were essential for ascospore development, hence indicating their involvement in post-fertilisation events. Neither pheromone precursor genes nor pheromone receptor genes of H. jecorina were transcribed in a strictly mating type dependent manner, but showed enhanced expression levels in the cognate mating type. In the presence of a mating partner under conditions favoring sexual development, transcript levels of pheromone precursors were significantly increased, while those of pheromone receptor genes do not show this trend. In the female sterile T. reesei strain QM6a, transcriptional responses of pheromone precursor and pheromone receptor genes to a mating partner were clearly altered compared to the female fertile wild-type strain CBS999.97. Consequently, a delayed and inappropriate response to the mating partner may be one aspect causing female sterility in QM6a.
Asunto(s)
Regulación Fúngica de la Expresión Génica/genética , Hypocrea/fisiología , Receptores de Feromonas/genética , Secuencia de Aminoácidos , ADN de Hongos/genética , Cuerpos Fructíferos de los Hongos/citología , Cuerpos Fructíferos de los Hongos/genética , Cuerpos Fructíferos de los Hongos/crecimiento & desarrollo , Cuerpos Fructíferos de los Hongos/fisiología , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Regulación del Desarrollo de la Expresión Génica , Genes del Tipo Sexual de los Hongos , Variación Genética , Hypocrea/citología , Hypocrea/genética , Hypocrea/crecimiento & desarrollo , Datos de Secuencia Molecular , Feromonas/metabolismo , Receptores de Feromonas/metabolismo , Alineación de Secuencia , Análisis de Secuencia de ADN , Eliminación de Secuencia , Esporas Fúngicas/citología , Esporas Fúngicas/genética , Esporas Fúngicas/crecimiento & desarrollo , Esporas Fúngicas/fisiologíaRESUMEN
The European species Hypocrea epimyces (Hypocreales, Ascomycota, Fungi) is redescribed based on the holotype including the drawing on its envelope by Saccardo and freshly collected material. The holomorphs of two closely related species, H. alni and H. brunneoviridis, are described as new species of the genus. They are characterized with morphological and molecular methods, including culture studies and phylogenetic analyses with internal transcribed spacers 1 and 2 as a part of the ribosomal RNA gene cluster, calmodulin, endochitinase, intron 4 of the translation elongation factor 1-alpha gene, and a part of the RNA polymerase II subunit B gene as phylogenetic markers. All species described here have green ascospores. Although phylogenetically closely related to H. lixii, they form reddish brown instead of green to black stromata. Except for H. brunneoviridis, forming nearly gliocladium-like conidiophores, the anamorphs of these species are similar to each other but vary in the angles of conidiophore branches and phialides, in phenotypic arrangement of conidiation on growth plates and in growth rates of cultures.