TRANSMISSION AND MODIFICATION OF TRANSFORMATION MARKERS DURING AN INDUCED PARASEXUAL CYCLE IN PENICILLIUM-ROQUEFORTI

Protoplasts of two wild-type strains of Penicillium roqueforti were transformed to hygromycin B and phleomycin resistance using resistance genes. DNAs were stably integrated into the fungal chromosomes. Protoplasts from transformed strains have been fused to produce diploid hybrids. After induced haploidization, seg-regants characterized by a reassortment of the parental genetic markers were isolated indicating that recombination had occurred during the parasexual cycle. Southern blot hybridization experiments revealed that transmission of the transformed phenotype was accompanied by extensive rearrangement and/or deletions dependent on the number of integrated plasmid copies. Methylation of cytosine residues of integrated DNA was also detected. These observations suggest that foreign DNA sequences transmitted during the parasexual cycle undergo modifications similar to the rearrangement of transformed characters induced premeiotically (RIP) through sexual crosses.