Fig. 2. Temperature-sensitive tsr mutantions. (A) Sequence comparisons of yeast, human and Drosophila cofilin sequences (Lappalainen et al., 1997). The cof1-22 mutation that gave a temperature sensitive phenotype in yeast is in red and denoted above the sequence. This mutation was used to predict and engineer a similar temperature-sensitive mutation in Drosophila, tsr¹³⁹, that is in red and denoted below the sequence. The position of the tsr^V27Q mutation is also indicated. (B) The cross generating tsr^V27Q/tsr¹³⁹; tsr⁹⁶ progeny. The conditional alleles P[w⁺, tsr¹³⁹] and P[w⁺, tsr^V27Q] together rescued the lethality caused by the tsr⁹⁶ mutation at the permissive temperature and allowed analysis of PCP defects in different tissues.