Figure 1. Conditional rac and cdc-42 mutants reveal cell polarity defects and aberrant hyphal morphogenesis.

(A) Stereomicroscopic analysis of N. crassa wild type, cdc42(18-4) and rac(7-1) grown at permissive conditions and shifted to 37°C for the indicated time or germinated at restrictive temperature. (B) Higher magnification and staining with FM4-64 revealed severe morphological defects of cdc42(18-4) and rac(7-1) grown at 37°C. Note that the dye accumulates within the apical region of the hyphal tip (white arrows), but a typical Spk (black arrow in wild type) is not formed. Arrowheads mark septa in the conditional strains.