Fig. 1

General diagram representing gene replacement via allelic exchange at the Y locus, and excision of the MLS^R marker by the FLP recombinase to create an unmarked Y deletion mutant. The boxed regions of X and Z genes represent approximatively the regions of homology incorporated into the replicative plasmid used for the double-crossover event (~ 1 kbp each). a Initial strategy used for the construction of the MGCΔcac1502 and MGCΔcac1502Δupp strains, b counter-selection strategy with the 5-FU/upp system used for the construction of the MGCΔcac1502ΔuppΔcac3535 strain