Isolation of heterothallic haploid
In order to get heterothallic haploid fom homothallic strains, spores of homothallic strains were mated with heterothallic haploid cells. Tetrads derived from homothallic diploid strains weresplit and arrayedonto 2% YPD plates. Then, a singlecdl of heterothallic NAM51-11D (MATu dse2 : : k{inMKsedl : : S17 bteura3ÅO) was attached to each spore and incubated at 30 ° C. Growing colonies were transferred to a 2% YPDA plate, incubated overnight at 30 ° C, and inoculated onto a SD+G418 plate. After a 24 h incubation at 30 ° C, colony: orming strains (uracil prototroph and G418-resistant) were considered diploids from the mating of NAM51-11D with the germinaced a-mating type spores, and these srraîns were then subjected to tetrad analysis to obtain acid-tolerant heterothalïic haploids.