Studies on a Temperature-sensitive Irreparable Mutant of Neurospora Crassa

Abstract

(1) Three temperature-sensitive mutants were obtained from a microconidial wild type strain of Neurospora crassa. One of them is irreparable at 34°C; that is, it grows as well as the wild type at 23°C, but does not grow on any (including omplete) medium so far tested at 34°C. This mutant was the major subject of this report.
(2) The temperature-sensitive irreparable mutant b39 differs from the parent strain by a single gene mutation. The gene responsible for the irreparable character is located on the first linkage group (mating type chromosome), about 30cM left of the centromere.
(3) This mutant does not inhibit the growth of the other temperature-sensitive strains in the heterocaryotic condition.
(4) The possibility of the accumulation of inhibitory substances by the mutant is unlikely, because the culture filtrate of the mutant did not inhibit the growth of the mutant at an intermediate temperature.
(5) The growth characteristics of the mutant when the culture was transfered from 23°C to 34°C, and from 34°C to 23°C were determined.
(6) The nature of the defect in an irreparable mutant was discussed.