INT1-induced filamentous growth is reduced by specific actin mutations. Shown are DIC micrographs of strains carrying the indicated ACT1 alleles (ACT1, YJB2603; act1-101, YJB2604; act1-104, YJB2614; act1-124, YJB2610; act1-129, YJB2611; act1-120, YJB2608) and expressing INT1 after growth on galactose for 16 h. Strains are listed in Tables 1 and 2.