RESUMO
In heterothallic ascomycetes one mating partner serves as the source of female tissue and is fertilized with spermatia from a partner of the opposite mating type. The role of pheromone signaling in mating is thought to involve recognition of cells of the opposite mating type. We have isolated two putative pheromone precursor genes of Magnaporthe grisea. The genes are present in both mating types of the fungus but they are expressed in a mating type-specific manner. The MF1-1 gene, expressed in Mat1-1 strains, is predicted to encode a 26-amino-acid polypeptide that is processed to produce a lipopeptide pheromone. The MF2-1 gene, expressed in Mat1-2 strains, is predicted to encode a precursor polypeptide that is processed by a Kex2-like protease to yield a pheromone with striking similarity to the predicted pheromone sequence of a close relative, Cryphonectria parasitica. Expression of the M. grisea putative pheromone precursor genes was observed under defined nutritional conditions and in field isolates. This suggests that the requirement for complex media for mating and the poor fertility of field isolates may not be due to limitation of pheromone precursor gene expression. Detection of putative pheromone precursor gene mRNA in conidia suggests that pheromones may be important for the fertility of conidia acting as spermatia.
Assuntos
Proteínas Fúngicas/genética , Genes Fúngicos , Genes Fúngicos Tipo Acasalamento , Magnaporthe/genética , Feromônios/genética , Precursores de Proteínas/genética , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , Cosmídeos/genética , DNA Complementar , DNA Fúngico/genética , Proteínas Fúngicas/química , Proteínas Fúngicas/metabolismo , Magnaporthe/crescimento & desenvolvimento , Magnaporthe/metabolismo , Dados de Sequência Molecular , Feromônios/biossíntese , Feromônios/química , Feromônios/metabolismo , Precursores de Proteínas/química , Precursores de Proteínas/metabolismo , RNA Fúngico/isolamento & purificação , Análise de Sequência de DNAAssuntos
Arsenicais/farmacologia , Células Eucarióticas/efeitos dos fármacos , Células Procarióticas/efeitos dos fármacos , Proteínas de Saccharomyces cerevisiae , Proteínas de Schizosaccharomyces pombe , Fatores de Transcrição , Animais , Arsenicais/química , Arsenicais/uso terapêutico , Bactérias/efeitos dos fármacos , Bactérias/metabolismo , Proteínas de Ligação a DNA/efeitos dos fármacos , Proteínas de Ligação a DNA/genética , Resistência a Medicamentos , Eucariotos/efeitos dos fármacos , Células Eucarióticas/parasitologia , Leucemia Experimental/tratamento farmacológico , Óperon/efeitos dos fármacos , Óperon/fisiologia , Saccharomyces cerevisiae/efeitos dos fármacosRESUMO
The cluster of three genes, ACR1, ACR2, and ACR3, previously was shown to confer arsenical resistance in Saccharomyces cerevisiae. The overexpression of ACR3 induced high level arsenite resistance. The presence of ACR3 together with ACR2 on a multicopy plasmid was conducive to increased arsenate resistance. The function of ACR3 gene has now been investigated. Amino acid sequence analysis of Acr3p showed that this hypothetical protein has hydrophobic character with 10 putative transmembrane spans and is probably located in yeast plasma membrane. We constructed the acr3 null mutation. The resulting disruptants were 5-fold more sensitive to arsenate and arsenite than wild-type cells. The acr3 disruptants showed wild-type sensitivity to antimony, tellurite, cadmium, and phenylarsine oxide. The mechanism of arsenical resistance was assayed by transport experiments using radioactive arsenite. We did not observe any significant differences in the accumulation of 76AsO33- in wild-type cells, acr1 and acr3 disruptants. However, the high dosage of ACR3 gene resulted in loss of arsenite uptake. These results suggest that arsenite resistance in yeast is mediated by an arsenite transporter (Acr3p).
Assuntos
Arsenitos/metabolismo , Proteínas Fúngicas/genética , Genes Fúngicos , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , Intoxicação por Arsênico , Transporte Biológico , Resistência Microbiana a Medicamentos , Proteínas de Membrana Transportadoras , Mutagênese Insercional , FenótipoRESUMO
A 4.2 kb region from Saccharomyces cerevisiae chromosome XVI was isolated as a yeast fragment conferring resistance to 7 mM-sodium arsenite (NaAsO2), when put on a multicopy plasmid. Homology searches revealed a cluster of three new open reading frames named ACR1, ACR2 and ACR3. The hypothetical product of the ACR1 gene is similar to the transcriptional regulatory proteins, encoded by YAP1, and YAP2 genes from S. cerevisiae. Disruption of the ACR1 gene conduces to an arsenite and arsenate hypersensitivity phenotype. The ACR2 gene is indispensable for arsenate but not for arsenite resistance. The hypothetical product of the ACR3 gene shows high similarity to the hypothetical membrane protein encoded by Bacillus subtilis ORF1 of the skin element and weak similarity to the ArsB membrane protein of the Staphylococcus aureus arsenical-resistance operon. Overexpression of the ACR3 gene confers an arsenite- but not an arsenate-resistance phenotype. The presence of ACR3 together with ACR2 on a multicopy plasmid expands the resistance phenotype into arsenate. These findings suggest that all three novel genes: ACR1, ACR2 and ACR3 are involved in the arsenical-resistance phenomenon in S. cerevisiae.
Assuntos
Intoxicação por Arsênico , Genes Fúngicos , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/genética , Sequência de Aminoácidos , Fatores de Transcrição de Zíper de Leucina Básica , Clonagem Molecular , Proteínas de Ligação a DNA/genética , Resistência Microbiana a Medicamentos/genética , Proteínas Fúngicas/genética , Amplificação de Genes , Dados de Sequência Molecular , Fenótipo , Proteínas Repressoras/genética , Mapeamento por Restrição , Homologia de Sequência de AminoácidosRESUMO
The gem2ts mutant of bacteriophage Mu induced synchrony of cell division on bacteria surviving infection. Induction of synchronous growth could also be observed as a response to the entire infected bacterial population, as in the case of infection of hic mutants, a peculiar class of gyrB alleles. After Mu wild-type or Mu gem2ts infection of hic mutants, there was a lack of viral DNA integration and replication, while phage gene expression (including that of A gene, coding for the transposase) seemed to be quite normal. These data indicate that the mechanism of bacterial synchronization induced by Mu gem2ts does not require integration nor replication of the phage DNA.
