A cloned 1.3-kb cDNA that hybridizes to genomic clone 549, containing genes predominantly expressed in the head of Drosophila melanogaster, was characterized. DNA sequencing showed that the cDNA-encoded protein is similar to a family of mammalian proteins, called 14-3-3, which activate tyrosine hydroxylase (TyrOHase) and tryptophan hydroxylase (TrpOHase), the two key enzymes regulating biosynthesis of biogenic monoamine neurotransmitters, such as dopamine and serotonin, in the brain. The putative D. melanogaster 14-3-3 protein (D14-3-3) shares 72.4, 74.3 and 78.3% amino acid (aa) sequence identity and 83.5, 87.7 and 85.9% aa sequence similarity with the beta, gamma and eta forms of bovine 14-3-3 protein, respectively. A lower (71%), but significant level of aa sequence identity was also found between D14-3-3 and sheep brain protein kinase C inhibitor protein (KCIP). The D14-3-3 gene expresses 1.0-, 1.9- and 2.9-kb mRNAs which show differential expression patterns. While the 2.9-kb mRNA is expressed only in the head, the other two mRNAs are found both in the head and body. Compared to the 1.9- and 2.9-kb mRNAs, the 1.0-kb mRNA is more abundant in the ovary and is probably maternally inherited. The 1.9-kb mRNA is the most predominant species in the embryos and its level peaks between 6-15 h of embryogenesis. The D14-3-3 gene is predominantly expressed in the ventral nerve cord of the embryo, and in the neural tissues of the head.(ABSTRACT TRUNCATED AT 250 WORDS)