CaLC4036: To generate a SWI4 homozygous deletion mutant, the NAT flipper cassette (pLC49)60 was PCR amplified using primers oLC3472 in combination with oLC3473 and transformed into CaLC239 (SN95). NAT-resistant transformants were PCR tested with oLC275 in combination with oLC3474 and oLC274 in combination with oLC3427. The SAP2 promoter was induced to drive expression of FLP recombinase to excise the NAT flipper cassette. Once again, the NAT flipper cassette (pLC49)60 was PCR amplified using primers oLC3472 in combination with oLC3473 and transformed into SWI4/swi4::FRT. NAT-resistant transformants were PCR tested as described above. The absence of a wild-type allele was verified with oLC3426 in combination with oLC3427, and the presence of deleted allele was verified by oLC3473 in combination with oLC3427. The SAP2 promoter was induced to drive expression of FLP recombinase to excise the NAT flipper cassette.