Different effects of temperature on recombination in lines of Neurospora crassa selected for high and for low recombination frequency

Abstract

Wild-type isolates of Neurospora crassa, picked out from lines selected for high and for low frequency of second division segregation (SDS) at 25oC for asco in linkage group (LG) VI, were scored for temperature effects on SDS-frequency for asco and on recombination frequencies in two adjacent intervals in LG II. Results obtained at 25oC and 17oC were compared. In the high selection line, the SDS-frequency for asco in both mating types (mt:s) decreased at 17oC compared to results obtained at 25oC. In the low selection line the SDS-frequency for asco in mt A increased at 17oC compared to results obtained at 25oC, while no significant effect of temperature on SDS-frequency for asco could be established in mt a. In LG II, temperature effects on recombination frequencies could only be established in the interval spanning the centromere, in one of the crosses involving an isolate from the high selection line. The recombination frequency increased at 17oC compared to results obtained at 25oC. The results are interpreted in terms of varying access in different genotypes, to gene products promoting and obstructing meiotic recombination, respectively.