Fig. 7. Arl1p regulates the integrity of the cell wall and localization of Gas1p in a GTP-dependent manner. (A) Congo Red hypersensitivity of an arl1 mutant overexpressing constitutively active Arl1p (Arl1Q72L), constitutively inactive Arl1p (Arl1T32N), and wild-type Arl1p. Different forms of Arl1p under the control of an ADH1 promoter were integrated into wild-type or arl1-mutant cells on the leu2 locus. Transformants were serially diluted and spotted on plates of YPAD, Congo Red (100 µg/ml), and Congo Red (100 µg/ml) containing 1.2 M sorbitol to examine their hypersensitivity. (B) The expression of constitutively inactive Arl1p (Arl1T32N) caused Congo Red hypersensitivity in wild-type cells. As described in A, different forms of Arl1p were introduced into wild-type cells and hypersensitivity to Congo Red was examined. (C) Effects of different forms of Arl1p in wild-type and arl1-mutant cells on localization of GFP-GPI (Gas1p). GFP-GPI was transformed into wild-type or arl1-mutant cells expressing different forms of Arl1p. After galactose induction, living cells were imaged using a Zeiss microscope.