Fig. 1.

Spontaneous iprodione resistance occurs through mutation of the hos1 gene. a Positions and nature of spontaneous mutations in iprodione resistant strains from four wild type strains relative to the exon (blue) and intron (grey) structure of the hos1 gene. The sequence alignments are of the wild type and mutant strains, with the nucleotide mutations that occurred in the four strains in red bold, and the predicted amino acid sequences underneath. The mutations in strains 14P290 and D2 cause frame shifts (the stop codon in the D2 mutant is underlined, in 14P290 the new stop codon is beyond the sequence shown). The mutations in M1 and D3 cause amino acid substitutions in residues that are invariant across hos1 homologs in the fungi. b A mutation in hos1 co-segregates with iprodione resistance. Growth of two parents and 14 progeny (from 28 total) of a D13 × D3-Ip^R cross between the parents on PDA with or without iprodione. The alleles of hos1 were assessed by PCR from genomic DNA of the two parents and 14 progeny from a cross between them, and subsequent digestion with AgeI restriction enzyme. M is the Invitrogen 1 kb + ladder. c Complementation of iprodione resistance back to sensitivity by the wild type hos1 gene. Mycelial plugs were inoculated onto PDA medium with or without iprodione (10 μg/ml) and cultured 4 days. The strains are four wild type strains, four spontaneous mutants derived from them, and the four strains whereby the wild type copy of hos1 was transformed into the mutants. The wild type copy of hos1 returned the strains to the wild type sensitive phenotype