Repeat-induced point mutations of HSP80 gene of Neurospora crassa: methylation of duplicated DNA sequences in the vegetative state.

The process of repeat-induced point mutations (RIP) was used to disrupt the gene encoding the 80-kDa heat-inducible protein of Neurospora crassa. Germinated conidia of the wild-type recipient strain were electrotransformed with a plasmid containing a 7-kb fragment harbouring the complete hsp80 gene sequence. Some of the transformants with a duplication of hsp80 gene sequence showed extensive methylation of these sequences even in vegetatively growing cells.

Disruption of the NAD(+)-specific glutamate dehydrogenase gene of Neurospora crassa by means of the RIP (repeat-induced point mutations) process.

The structural gene for the catabolite-repressed, substrate-induced NAD(+)-specific glutamate dehydrogenase (gdh-1) of Neurospora crassa was disrupted using the process of repeat-induced point mutation (RIP). Plasmids containing incomplete copies of the gene, along with selectable markers, were introduced into germinated conidia by electroporation. The sexual progeny of a transformant containing an ectopically integrated copy of a plasmid, harbouring the 5' flanking region and a part of the coding sequence of gdh-1 DNA, was examined for the occurrence of RIP by (i) Southern blot analysis of the genomic DNA digested with the isoschizomers MboI and Sau3A, (ii) Northern blot analysis of total RNA in cultures subjected to repression and induction conditions for NAD-GDH, (iii) direct assessment of enzymatic activity, and (iv) evaluation of protein levels by Western blot analysis using a polyclonal anti-GDH IgG preparation.

NAD(+)-specific glutamate dehydrogenase of Neurospora crassa: cloning, complete nucleotide sequence, and gene mapping.

The NAD(+)-specific glutamate dehydrogenase (NAD-GDH) of the filamentous fungus Neurospora crassa is a tetrameric enzyme, regulated by catabolite repression. The amino acid sequence of this enzyme had been published several years ago. With the object of investigating the molecular mechanism of catabolite repression, the nucleotide sequence of genomic clones containing the coding region, along with 5'- and 3'-flanking noncoding segments of the NAD-GDH transcription unit, was obtained.