FIG. 9.

Schematic representations of the fate of bisformyl dityrosine in sporulating wild-type and mutant cells. Bisformyl dityrosine (black circles) is synthesized from free l-tyrosine (gray circles) in the cytoplasm of the prospores in a two-step reaction catalyzed by Dit1p, the cytochrome P-450 Dit2p, and the NADPH-cytochrome P-450 reductase Cpr1p. (A) In the wild type, bisformyl dityrosine is transported through the prospore membrane by Dtr1p and incorporated into the maturing spore wall. (B) The absence of Dtr1p results in the accumulation of bisformyl dityrosine in the prospore cytoplasm and often in an altered structure of the spore surface. (C) In cda1,cda2-Δ cells, bisformyl dityrosine is translocated through the prospore membrane by Dtr1p but not incorporated into the spore wall because of the altered spore wall structure. From the ascal cytoplasm, bisformyl dityrosine eventually diffuses through the ascus wall and accumulates in the medium. (D) The additional deletion of DTR1 in cda1,cda2,dtr1-Δ cells prevents the release into the medium, because bisformyl dityrosine is retained within the prospore. PSM, prospore membrane; SW, spore wall; AW, ascus wall.