Carrefour Mme. Gras: a wild-isolated Neurospora crassa strain that suppresses meiotic silencing by unpaired DNA and uncovers a novel ascospore stability defect

Abstract

Ordinarily, RIP-induced erg-3 mutant Neurospora crassa ascospores and their erg⁺ siblings do not differ in stability during long-term storage. Consequently, the frequency of RIP-induced erg-3 mutants remains about constant regardless of the time that has elapsed between ascospore harvest and germination. We found, however, that RIP-induced erg-3 mutants were apparently selectively lost with time from among the ascospores stored from a cross with the wild-isolated Carrefour Mme. Gras strain from Haiti. The Haitian strain was also found to exert a dominant suppression of meiotic silencing by unpaired DNA. Similar loss of RIP-induced erg-3 mutant ascospores was seen among the stored ascospores from a subset of crosses heterozygous for the semi-dominant Sad-1 or Sad-2 suppressors of meiotic silencing. Our results suggest that crosses suppressed in meiotic silencing can compromise the stability during storage of ascospores that inherit RIP-induced mutations.