FIG 4 .

IRD truncation abrogates RasA function. (A) Comparison of germination rates between the control strain and the RasAΔIRD mutant. Equal numbers of conidia were inoculated onto AMM broth and incubated at 37°C. At the noted time points, samples were removed, and 100 random conidia from each strain were scored for germ tube production (polarity establishment). Data are presented as the percentage of germinated conidia for each time point. (B) Representative micrographs of germinating conidia from each strain after 5 h of incubation at 37°C. Note the irregular conidial size of the RasAΔIRD mutant, indicating higher variability in the timing of germination initiation. (C) Representative micrographs of hyphal development aberrancies in the RasAΔIRD mutant after 16 h of growth at 37°C. Conidia from each strain were cultured as described for the germination studies. Note the stunted, highly branched hyphae produced by RasAΔIRD. (D) Representative micrographs of conidiophore development in the control strain and RasAΔIRD mutant. After 24 h of culture at 37°C on AMM agar, the control strain produced conidiophores with swollen vesicles and numerous conidia arranged in chains (left panel). The RasAΔIRD mutant produced no conidiophores at 24 h of identical culture (data not shown) and produced distorted conidiophore structures by 48 h (right panel), characterized by minimally swollen vesicles and few conidia.