RESUMO
Colletotrichum coccodes (Wallr.) Hughes is an asexual fungus with five vegetative compatibility groups. It was postulated that C. coccodes was isolated at the center of origin of potato at one time, and due to the movement of potato around the globe, the fungus was established on each continent but became bottlenecked and genetically unable to form stable heterokaryons via vegetative compatibility grouping (VCG) studies. The objectives of this study were (i) to determine if the VCGs around the world are related to the VCGs in Chile, (ii) to determine the diversity of C. coccodes populations in Chile, and (iii) to find any evidence for a cryptic sexual life cycle for this fungus. Worldwide C. coccodes populations have been found to be genetically correlated and belong to one or more C. coccodes-identified VCGs. The most distributed VCG in Chile was VCG2, which is the most common VCG in North America. We hypothesize that one or more VCGs had spread from Chile to the rest of the world. Precautions and further studies should be investigated by using other molecular markers and gene sequencing.
RESUMO
The fungal zinc finger transcription factor NsdC is named after, and is best known for, its essential role in sexual reproduction (never in sexual development). In previous studies with Aspergillus nidulans, it was also shown to have roles in promotion of vegetative growth and suppression of asexual conidiation. In this study, the function of the nsdC homologue in the opportunistic human pathogen A. fumigatus was investigated. NsdC was again found to be essential for sexual development, with deletion of the nsdC gene in both MAT1-1 and MAT1-2 mating partners of a cross leading to complete loss of fertility. However, a functional copy of nsdC in one mating partner was sufficient to allow sexual reproduction. Deletion of nsdC also led to decreased vegetative growth and allowed conidiation in liquid cultures, again consistent with previous findings. However, NsdC in A. fumigatus was shown to have additional biological functions including response to calcium stress, correct organization of cell wall structure, and response to the cell wall stressors. Furthermore, virulence and host immune recognition were affected. Gene expression studies involving chromatin immunoprecipitation (ChIP) of RNA polymerase II (PolII) coupled to next-generation sequencing (Seq) revealed that deletion of nsdC resulted in changes in expression of over 620 genes under basal growth conditions. This demonstrated that this transcription factor mediates the activity of a wide variety of signaling and metabolic pathways and indicates that despite the naming of the gene, the promotion of sexual reproduction is just one among multiple roles of NsdC.IMPORTANCEAspergillus fumigatus is an opportunistic human fungal pathogen and the main causal agent of invasive aspergillosis, a life-threatening infection especially in immunocompromised patients. A. fumigatus can undergo both asexual and sexual reproductive cycles, and the regulation of both cycles involves several genes and pathways. Here, we have characterized one of these genetic determinants, the NsdC transcription factor, which was initially identified in a screen of transcription factor null mutants showing sensitivity when exposed to high concentrations of calcium. In addition to its known essential roles in sexual reproduction and control of growth rate and asexual reproduction, we have shown in the present study that A. fumigatus NsdC transcription factor has additional previously unrecognized biological functions including calcium tolerance, cell wall stress response, and correct cell wall organization and functions in virulence and host immune recognition. Our results indicate that NsdC can play novel additional biological functions not directly related to its role played during sexual and asexual processes.
Assuntos
Aspergillus fumigatus/genética , Aspergillus fumigatus/metabolismo , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Animais , Aspergilose/microbiologia , Aspergilose/patologia , Aspergillus fumigatus/patogenicidade , Parede Celular , Modelos Animais de Doenças , Feminino , Regulação Fúngica da Expressão Gênica , Genes Fúngicos/genética , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Mutação , Fenótipo , Reprodução Assexuada , Transdução de Sinais , Transcriptoma , Virulência/genética , Fatores de Virulência/genéticaRESUMO
Toxoplasma gondii is a widely prevalent protozoan parasite member of the phylum Apicomplexa. It causes disease in humans with clinical outcomes ranging from an asymptomatic manifestation to eye disease to reproductive failure and neurological symptoms. In farm animals, and particularly in sheep, toxoplasmosis costs the industry millions by profoundly affecting their reproductive potential. As do all the parasites in the phylum, T. gondii parasites go through sexual and asexual replication in the context of an heteroxenic life cycle involving members of the Felidae family and any warm-blooded vertebrate as definitive and intermediate hosts, respectively. During sexual replication, merozoites differentiate into female and male gametes; their combination gives rise to a zygotes which evolve into sporozoites that encyst and are shed in cat's feces as environmentally resistant oocysts. During zygote formation T. gondii parasites are diploid providing the parasite with a window of opportunity for genetic admixture making this a key step in the generation of genetic diversity. In addition, oocyst formation and shedding are central to dissemination and environmental contamination with infectious parasite forms. In this minireview we summarize the current state of the art on the process of gametogenesis. We discuss the unique structures of macro and microgametes, an insight acquired through classical techniques, as well as the more recently attained molecular understanding of the routes leading up to these life forms by in vitro and in vivo systems. We pose a number of unanswered questions and discuss these in the context of the latest findings on molecular cues mediating stage switching, and the implication for the field of newly available in vitro tools.
Assuntos
Toxoplasma , Toxoplasmose Animal , Animais , Gatos , Feminino , Gametogênese , Masculino , Oocistos , Ovinos , Esporozoítos , Toxoplasma/genéticaRESUMO
The genus Colletotrichum comprises species with different lifestyles but is mainly known for phytopathogenic species that infect crops of agronomic relevance causing considerable losses. The fungi of the genus Colletotrichum are distributed in species complexes and within each complex some species have particularities regarding their lifestyle. The most commonly found and described lifestyles in Colletotrichum are endophytic and hemibiotrophic phytopathogenic. Several of these phytopathogenic species show wide genetic variability, which makes long-term maintenance of resistance in plants difficult. Different mechanisms may play an important role in the emergence of genetic variants but are not yet fully understood in this genus. These mechanisms include heterokaryosis, a parasexual cycle, sexual cycle, transposable element activity, and repeat-induced point mutations. This review provides an overview of the genus Colletotrichum, the species complexes described so far and the most common lifestyles in the genus, with a special emphasis on the mechanisms that may be responsible, at least in part, for the emergence of new genotypes under field conditions.
Assuntos
Colletotrichum/crescimento & desenvolvimento , Colletotrichum/genética , Variação Genética/genética , Doenças das Plantas/microbiologia , Elementos de DNA Transponíveis/genética , Endófitos , Genoma Fúngico/genética , Especificidade de Hospedeiro , Sequências Repetitivas de Ácido Nucleico/genética , Especificidade da EspécieRESUMO
Objetivo. Estudiar el ciclo sexual y la fecundidad del pejerrey patagónico, especie de alto valor comercial y deportivo, en el embalse Ezequiel Ramos Mexía (Neuquén, Río Negro; Argentina). Materiales y métodos. Se colectaron 9307 ejemplares. El ciclo sexual se estudió mediante la observación macroscópica de las gónadas y la fecundidad absoluta se calculó con la técnica volumétrica. Resultados. La talla de primera madurez sexual (Lm 50%) se estimó a través del ajuste de una curva logística. El desove tuvo lugar en primavera y principios de verano (septiembre a diciembre). La talla de primera madurez sexual, en las hembras, fue de 244,37 mm (Lt). La fecundidad absoluta varió entre 3.976 ovocitos en una hembra de 296 mm (Lt) y 190 g y 20.879 ovocitos en una hembra de 420 mm (Lt) y 704 g. Conclusiones. No se observó una relación significativa entre la fecundidad relativa y la longitud total de los ejemplares. La proporción de sexos resultó equilibrada en las clases de longitud intermedias, pero mostró una preponderancia de hembras en las mayores. El ciclo ovárico es altamente estacional y coincide con el de poblaciones de la especie en otros ambientes patagónicos. La fecundidad, en cambio, resultó más elevada que la observada en el lago Moreno, situado en la región cordillerana.
Objective. To study the sexual cycle and fecundity of the Patagonian silverside, a species of high commercial and sport value, from Ezequiel Ramos Mexia reservoir (Neuquen, Rio Negro; Argentina ). Materials and methods. Sampling was conducted between 1982 and 1986, and 9307 specimens were collected. The sexual cycle was studied by macroscopic observation of the gonads and fecundity was assessed using the volumetric method. Results. Length at first maturity (Lm 50%) was estimated by fitting a logistic curve. Spawning took place in spring and early summer (September to December). Length at first maturity was 244.37 mm (Lt) in females. Absolute fecundity ranged between 3.976 oocytes in a 296 mm (Lt), 190 g female and 20.879 oocytes in a 420 mm (Lt), 704 g female. Conclusions. No significant relation was found between relative fecundity and total length. The sex ratio was approximately 1:1 at intermediate length classes, but females predominated in the larger classes. The ovarian cycle was highly seasonal and coincided with that of populations from other Patagonian environments. Fecundity, on the other hand, was higher than that observed at Moreno Lake, in the Andean region.
Assuntos
Fertilidade , Argentina , ReproduçãoRESUMO
Physalaemus henselii (Peters, 1872) es un pequeño leiupérido que no ha sido estudiado desde los años 60. Aquí redescribimos su canto de anuncio, y determinamos su ciclo sexual femenino y el período reproductivo en base al análisis macroscópico de los ovarios y de observaciones de campo. Fue calculado el Factor de Tamaño Ovárico (FTO). El estudio fue realizado en el Departamento de Rivera, norte de Uruguay. El canto nupcial consiste en notas cortas (177 ± 21ms) y multipulsadas (20 ± 3 pulsos/nota), con una tasa de repetición de notas de 1.57 ± 0.13 notas/s. Physalaemus henselii tiene un ciclo sexual femenino con distribución unimodal de hembras maduras, las que están presentes de Febrero a Setiembre. El FTO y la tasa "hembras con ovocitos maduros / hembras sin ovocitos maduros" alcanzó los valores más altos desde Abril a Junio. El número y tamaño de los ovocitos estuvieron correlacionados positivamente con el tamaño de las hembras. La hembra más pequeña (SVL =18.94mm, masa =0.78g) con ovocitos maduros fue encontrada en Julio. El ciclo sexual observado, con un solo periodo reproductivo anual durante la estación fría (otoño e invierno temprano), constituye un hecho poco frecuente en las especies de anuros de la región.
Physalaemus henselii (Peters, 1872) is a little known leiuperid frog that has not been studied since the 1960s. Herein, we redescribe its advertisement call, and assess the female sexual cycle and the reproductive period on the basis of the macroscopic analysis of the ovaries and field observations. The Ovarian Size Factor (OSF) was calculated. The study was made in Departamento de Rivera, northern Uruguay. The advertisement call consists of short (177 ± 21ms), multipulsed (20 ± 3 pulses/note) notes, with a note repetition rate of 1.57 ± 0.13 notes/s. Physalaemus henselii has a female sexual cycle with unimodal distribution of gravid females, which are present from February to September. The OSF and the ratio "females with mature oocytes / females without mature oocytes" reached the highest values from April to June. The number and size of oocytes were positively correlated with female size. The smallest female (SVL =18.94mm, weight =0.78g) with mature oocytes was found in July. The observed sexual cycle with a single annual reproductive period during the cold season (autumn and early winter), is an uncommon fact for anuran species in the region.
RESUMO
Physalaemus henselii (Peters, 1872) es un pequeño leiupérido que no ha sido estudiado desde los años 60. Aquí redescribimos su canto de anuncio, y determinamos su ciclo sexual femenino y el período reproductivo en base al análisis macroscópico de los ovarios y de observaciones de campo. Fue calculado el Factor de Tamaño Ovárico (FTO). El estudio fue realizado en el Departamento de Rivera, norte de Uruguay. El canto nupcial consiste en notas cortas (177 ± 21ms) y multipulsadas (20 ± 3 pulsos/nota), con una tasa de repetición de notas de 1.57 ± 0.13 notas/s. Physalaemus henselii tiene un ciclo sexual femenino con distribución unimodal de hembras maduras, las que están presentes de Febrero a Setiembre. El FTO y la tasa "hembras con ovocitos maduros / hembras sin ovocitos maduros" alcanzó los valores más altos desde Abril a Junio. El número y tamaño de los ovocitos estuvieron correlacionados positivamente con el tamaño de las hembras. La hembra más pequeña (SVL =18.94mm, masa =0.78g) con ovocitos maduros fue encontrada en Julio. El ciclo sexual observado, con un solo periodo reproductivo anual durante la estación fría (otoño e invierno temprano), constituye un hecho poco frecuente en las especies de anuros de la región.
Physalaemus henselii (Peters, 1872) is a little known leiuperid frog that has not been studied since the 1960s. Herein, we redescribe its advertisement call, and assess the female sexual cycle and the reproductive period on the basis of the macroscopic analysis of the ovaries and field observations. The Ovarian Size Factor (OSF) was calculated. The study was made in Departamento de Rivera, northern Uruguay. The advertisement call consists of short (177 ± 21ms), multipulsed (20 ± 3 pulses/note) notes, with a note repetition rate of 1.57 ± 0.13 notes/s. Physalaemus henselii has a female sexual cycle with unimodal distribution of gravid females, which are present from February to September. The OSF and the ratio "females with mature oocytes / females without mature oocytes" reached the highest values from April to June. The number and size of oocytes were positively correlated with female size. The smallest female (SVL =18.94mm, weight =0.78g) with mature oocytes was found in July. The observed sexual cycle with a single annual reproductive period during the cold season (autumn and early winter), is an uncommon fact for anuran species in the region.