Fig. 3.

Confirmation of the lack of complete disruption of FTR1 in the multinucleated R. oryzae. (A) DAPI stain of swollen R. oryzae spores showing the presence of multiple nuclei with a single spore. Arrows denote nuclei. Original magnification, x1000. (B) Gel electrophoresis showing lack of amplification of FTR1 after 14 passages of the putative null mutants on iron-rich medium (1000 μM FeCl₃) and amplification of the FTR1 from the same isolate following growth on iron-depleted medium (i.e. 100 μM ferrioxamine) for 96 h. Amplification of actin (600 bp) was used to confirm the integrity of DNA used as template and the absence of PCR inhibitors. (C) Southern blot confirming the integration of the disruption cassette in the putative ftr1 (7380 bp band is present only in DNA sample extracted from putative ftr1 grown in iron-rich medium) and almost complete elimination of the FTR1 copy (lack of 1960 bp in DNA sample extracted from putative ftr1 grown in iron-rich medium).