Figure 2.

The Smc5–Smc6 complex acts after DSB formation and strand invasion during meiotic recombination. (A) Cells lacking Nse6 or Nse5 form aberrant asci following meiosis. Mature asci (phase microscopy on the left or DAPI stained on the right) outlined with a dashed line, from genetic crosses of wild-type, nse5Δ, nse6Δ and mus81Δ cells. Two days after mating, wild-type asci show four spores of equal size, each containing DNA. nse5Δ, nse6Δ and mus81Δ mutants do not form well-defined spores, with progeny often having only one large spore. (B) The low spore viability of nse6Δ, mus81Δ and the nse6Δ mus81Δ double mutant is rescued by deleting rec12. The percentage of asci with either a wild-type appearance (four well-defined spores of equal size) or aberrant phenotypes including triads, dyads (typical for rec12Δ), or a single large spore, or four very small spores (as observed in nse6Δ cells) was determined. Spore viabilities were scored for crosses of the indicated genotypes. Data shown are the averages from three independent crosses, and around 100 asci were counted for each cross. (C) Nse6 acts after the Rad51 and Dmc1 strand-exchange proteins. The percentage of asci produced from a genetic cross of rec12Δ, rad51Δ, dmc1Δ and mus81Δ strains (either as single or double mutants) in the presence or absence of Nse6 is shown. Black areas indicate spores of various sizes and shapes.