Skip to main content
. 2000 Oct;11(10):3525–3537. doi: 10.1091/mbc.11.10.3525

Figure 5.

Figure 5

DAPI staining and electron microscopy of wild-type and mps1 mutant strains reveals a spore wall defect. Cells were fixed for 15 min with 3.7% formaldehyde and stained with 1 μg/ml DAPI for <5 min (see MATERIALS AND METHODS). DAPI permeation into the interior of the spore is retarded by mature spore walls in wild-type MPS1 (YUMY4B1) (A). Lack of complete spore wall formation in the mps1 mutant strains allows DAPI to readily stain DNA within individual spores of mps1-1237 (YUMY4C6) (B), mps1-412 (YUMY4B5) (C), mps1-1 (YUMY4C9) (D), and mps1-3796 (YUMY4C2) (E). Note that in D and E, meiotic chromosome segregation fails as expected, and the cells build defective spore walls. Also note the fragmentation of DAPI-staining material within the mutant spores. Thin-section electron microscopy of MPS1 (YUMY4F4) (F), mps1-1237 (YUMY071) (G), and mps1-3796 (YUMY070) (H) strains displays the heterogeneous nature of the spore wall defect caused by mps1 mutation. (F) Wild-type spores have a four-layered structure that is relatively uniform in thickness. Mature spores are tightly associated in a tetrahedral array within a condensed ascus. Darkly staining material defines the outer, dityrosine-containing layer of the spore wall, and electron-dense material is seen adjoining individual spores (arrow). (G) Two to four spores are produced in mps1-1237 strains, and individual spores lack the organization of the spore wall seen in wild-type. Spore wall thickness is more variable than in wild- type, with component layers of spore wall material not organized as in wild-type. The electron-dense outer layer of the mutant spores is often missing, and the asci tend not to condense around tightly adherent spores. Note that the very electron-dense material connecting the MPS1 spores is disrupted in the mps1-1237 ascus (arrow). Up to 15% of cells containing the mps1-3796 allele eventually form an aberrant single spore body (H, arrowhead). The spore produced in these cells reveals similar structural defects as in a mps1-1237 strain. Bars, 0.7 μm