Fig. 5. An atypical histidine in the switch I region of AgRho1a. (A) Alignment of the switch I region of Rho-type proteins from several model organisms. Non-homologous residues are shaded gray. The residue corresponding to position 39 of AgRho1a is boxed. (B) An A. gossypii mutant with an exchange of histidine 39 for tyrosine (C115T) in AgRho1a can complement the lethality of Agrho1b. Spores from mycelia that are heterokaryotic for the indicated mutation were spotted on plates selective for the markers of the mutations. Plates were incubated for 4 days at 30°C. (C) Growth speed of the mutants shown in B. Identically sized inoculums of homokaryotic mycelia were placed on full medium plates and incubated at 30°C for 4 days. Growth speed was determined as the quotient of mycelial diameter and incubation time. (D) The AgRho1aH39Y mutant is able to complement the deletion of ScRHO1 in S. cerevisiae. Yeast cells were grown at 25°C in liquid medium to OD₆₀₀=1 and diluted. The indicated cell numbers were spotted on agar plates and were incubated at the indicated temperatures for 2 days. (E) GFP-AgRho1aH39Y displays an altered localization pattern at 25°C compared with GFP-AgRho1a. Growth conditions were identical to Fig. 3. Bar, 10 µm.