Assuntos
Masculino , Feminino , Humanos , Genética/classificação , Genética/educação , Genética/instrumentaçãoAssuntos
Humanos , Masculino , Feminino , Genética/classificação , Genética/educação , Genética/instrumentaçãoAssuntos
Masculino , Feminino , Humanos , Genética/classificação , Genética/educação , Genética/instrumentaçãoAssuntos
Humanos , Masculino , Feminino , Genética/classificação , Genética/educação , Genética/instrumentaçãoRESUMO
Actin has a pivotal function in hyphal morphogenesis in filamentous fungi, but it is not certain whether its function is equivalent to that of a morphogen, or if it is simply part of a mechanism that executes orders given by another regulatory entity. To address this question we selected for cytochalasin A resistance and isolated act1, the first actin mutant in Neurospora crassa. This mutant branches apically and shows an altered distribution of actin at the tip. Based on the properties of this mutant, we propose a model of tip growth and branching in which actin effects tip growth by regulating the rate of vesicle flow from proximal to distal regions of a hypha, thereby controlling the tip-high gradient of cytoplasmic calcium. The actin-controlled calcium gradient at the tip is necessary for maintenance of tip growth as well as the dominance of one polarized site at the hyphal tip. The phenotype of act1 indicates that actin controls the balance between lateral and apical branching.
Assuntos
Actinas/genética , Actinas/fisiologia , Genes Fúngicos , Neurospora crassa/crescimento & desenvolvimento , Neurospora crassa/genética , Actinas/metabolismo , Cálcio/metabolismo , Polaridade Celular , Clonagem Molecular , Citocalasinas/farmacologia , Citoplasma/química , Vesículas Citoplasmáticas/metabolismo , Proteínas do Citoesqueleto/genética , Proteínas do Citoesqueleto/fisiologia , Farmacorresistência Fúngica/genética , Proteínas Fúngicas/genética , Proteínas Fúngicas/fisiologia , Hifas/citologia , Hifas/crescimento & desenvolvimento , Morfogênese/genética , Mutação , Neurospora crassa/citologia , Seleção Genética , TemperaturaRESUMO
In N. crassa and N. intermedia, the kalilo plasmid triggers senescence by insertion into mitochondrial DNA. To investigate the cell death pathway induced by this plasmid, juvenile and senescent subcultures of several senescent strains were examined by light and transmission electron microscopy, and at the DNA level. There were no signs of apoptotic events, such as shrinkage of the cytoplasm away from the cell wall, apoptotic bodies, internucleosomal DNA fragmentation or condensation of the cytoplasm while retaining mitochondria and endomembrane structure. Instead, swollen mitochondria lacking cristae and containing amorphous inclusions, and disruption of nuclear and mitochondrial membranes indicated a necrotic mode of cell death.