(A) Model of the subunit arrangement in the yeast septin hetero-octamer (McMurray & Thorner, 2008); Cdc3 (blue), Cdc10 (brown); Cdc11 (pink); Cdc12 (green). (B) Sequence conservation of the Trp contact residue in the G interface. (C) Cultures of the indicated genotypes were grown in YPGal, spotted in five-fold serial dilutions onto agar plates containing SCGal-Leu medium in the absence (left) or presence (right) of FOA to select against URA3-containing cells, and photographed after incubation at RT for 5–6 dy. Far right, schematic depiction of septin composition in cells that have lost the URA3 plasmid; red asterisk, W267A mutation at G interface of Cdc12. (D) Strains MJY201 and JTY3631 were crossed, generating (after loss of a URA3-marked plasmid) the indicated cdc11Δ0::HIS3MX/CDC11+ shs1Δ0::kanMX/SHS1+ diploid, which was subjected to sporulation and tetrad dissection. Shown are representative meiotic progeny of the indicated genotypes after incubation on YPD medium at 26° for 4 dy. Far right, representative image of the type of microcolony formed by the cdc11Δ SHS1+ spores, which all failed to form a viable clone. (E) As in (C), except that the cdc11Δ cells also lacked Shs1. See also Figure S1.