Although the full genome sequence is known, this is just the beginning of what has been called the "postgenomic era". Projects are under way to annotate the function of each of the genes revealed by sequencing. An important part of this program is to systematically knock out each gene to see its effect on phenotype.
2. SILENCING MECHANISMS
There are three interesting silencing processes, all of which concern the fate of extra copies of genetic material. First, RIP (repeat-induced point mutation) induces GC to AT mutations in duplicated material, just prior to meiosis during a cross. Second, meiotic silencing inactivates any meiotic gene that is unpaired at meiosis (the MAT alleles are an exception). Third, quelling postranscriptionally silences duplicate sequences in asexual cells.
3. SELF-NONSELF RECOGNITION
In natural populations there are polymorphisms for heterokaryon incompatibility (het) genes. If two strains are different for any pair of het alleles, they will not form a heterokaryon; instead their contact promotes a cell death reaction. The mechanisms of death are a subject of current research. Some have counterparts in higher eukaryote apoptosis; others resemble prion mechanisms.
4. DIURNAL RHYTHM
Neurospora strains show a 24 hour rhythm of conidiation. This is produced by a genetic program in combination with various environmental inputs. This system is highly amenable to genetic analysis through mutations that change the working of the endogenous "clock".
5. MORPHOGENESIS
Apical growth and branching (keys to morphogenesis) have been called the "Hallmark" of fungi, yet their mechanisms are not well understood. Many useful mutations affecting this progress are available, whose effects are being deciphered. Current models involve delivery of membrane/wall vesicles by the cytoskeleton to the apical Spizenkörper, an organelle that seems to distribute vesicles to the expanding dome.
6. BIOGEOGRAPHY AND EVOLUTION
The species of Neurospora with their different life cycles are found all over the world, in many climates and in many habitats. This provides a useful system for the study of adaptation and speciation.
7. MITOCHONDRIAL BIOGENESIS
Although the mitochondrial DNA sequence has been known for many years, the piecing-together of the mechanisms whereby nucleus- and mitochondrially-encoded proteins functionally unite in the mitochondrion is an ongoing challenge. In addition, wild Neurosporas have many natural plasmids whose origin and significance are still a mystery.
Last modified 8/5/04 KMC