Analysis of the Sequence and Phenotype of Drosophila Sex combs reduced Alleles Reveals Potential Functions of Conserved Protein Motifs of the Sex combs reduced Protein (original) (raw)

The Drosophila Hox gene, Sex combs reduced (Scr), is required for patterning the larval and adult, labial and prothoracic segments. Fifteen Scr alleles were sequenced and the phenotypes analyzed in detail. Six null alleles were nonsense mutations (Scr 2 , Scr 4 , Scr 11 , Scr 13 , Scr 13A , and Scr 16) and one was an intragenic deletion (Scr 17). Five hypomorphic alleles were missense mutations (Scr 1 , Scr 3 , Scr 5 , Scr 6 , and Scr 8) and one was a small protein deletion (Scr 15). Protein sequence changes were found in four of the five highly conserved domains of SCR: the DYTQL motif (Scr 15), YPWM motif (Scr 3), Homeodomain (Scr 1), and C-terminal domain (CTD) (Scr 6), indicating importance for SCR function. Analysis of the pleiotropy of viable Scr alleles for the formation of pseudotracheae suggests that the DYTQL motif and the CTD mediate a genetic interaction with proboscipedia. One allele Scr 14 , a missense allele in the conserved octapeptide, was an antimorphic allele that exhibited three interesting genetic properties. First, Scr 14 /Df had the same phenotype as Scr 1 /Df. Second, the ability of the Scr 14 allele to interact intragenetically with Scr alleles mapped to the first 82 amino acids of SCR, which contains the octapeptide motif. Third, Scr 6 , which has two missense changes in the CTD, did not interact genetically with Scr 14 .