DISRUPTION OF THE GENE ENCODING THE 78-KILODALTON SUBUNIT OF THE PERIPHERAL ARM OF COMPLEX-I IN NEUROSPORA-CRASSA BY REPEAT INDUCED POINT MUTATION (RIP)

We have used the procedure of sheltered RIP to generate mutants of the 78-kDa protein of the peripheral arm of Neurospora crassa complex I. The nuclei containing the mutations were initially isolated as one com ponent of a heterokaryon but subsequent analysis showed that nuclei co ntaining null alleles of the gene could be propagated as homokaryons. This demonstrates that the gene does not serve an essential function. Sequence analysis of one allele shows that 61 transition mutations wer e created resulting in 39 amino-acid changes including the introductio n of four stop codons. Mutant strains grow at a slower rate than wild- type and exhibit a decrease in the production of conidia. Electron par amagnetic spectroscopy of mutant mitochondria suggest that they are de ficient in Fe-S clusters N-1, N-3, and N-4.