Genetics of Neurospora

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Ongoing projects take advantage of this laboratory's long experience with Neurospora biology and genetics. The projects concern mutational and epigenetic gene silencing, developmental events in the ascus, meiotic drive, and the delineation of species. Most of the experiments center on the sexual phase of the life cycle and exploit features of Neurospora that make it advantageous for investigations that cannot be readily carried out with yeast. Examples include the following: (1) Genetics and programming of ascus development. The expression and sites of action of genes known to affect the sexual phase will be examined using green fluorescent protein (GFP). Microscopic studies will continue on the effect of unpaired DNA in silencing genes that are expressed in the sexual phase.. (2) The reproductive genetics and biology of N. tetrasperma. Ascus development in this species is reprogrammed to produce self-fertile heterokaryotic products. Crossing over is abolished between the mating type locus and the centromere and recombination is also blocked over most of the mating-type chromosome. The genetic basis of the block is being studied, and modes of ascus programming are being examined in 4-spored species of other genera. (3) Cryptic drive elements in N. tetrasperma. In 8-spored asci, ascospores with sensitive nuclei are killed in crosses that are heterozygous for a Spore-killer meiotic drive element (Sk). Sensitive nuclei survive, however, if they are enclosed in the same ascospore with a killer nucleus. Because N. tetrasperma normally has two types of nuclei in each heterokaryotic ascospore, Sk elements may be present even though they are not apparent. Experiments with strains from natural populations will examine this possibility. (4) A locus-specific mutator. Crosses involving a particular allele of the eas gene in N. crassa produce progeny that are mutated at a specific unlinked locus. The behavior suggests that a duplicate copy of the target gene is linked to the eas mutation, resulting in RIP (repeat induced point mutation). This hypothesis is being tested using crosses homozygous for a mutant that is deficient in RIP.This laboratory has long been devoted to developing Neurospora as a model organism. Model organisms are great assets to science, for the insights gained from them can be used to guide and often accelerate studies of other related but less well-understood organisms. The vast store of genetic and biological information to which the laboratory has contributed makes Neurospora an ideal reference organism with which to compare other filamentous fungi, including plant and animal pathogens, commercially important species, and innumerable ecologically important forms.