Comparison on ebony gene from three ebony mutants

ROSSI, F.A.; QUESADA-ALLUÉ, L.A.; PÉREZ, M.M.

DROSOPHILA INFORMATION SERVICE

University of Oklahoma

Lugar: Oklahoma; Año: 2014 vol. 97 p. 30 - 32

0070-7333

Drosophila melanogaster ebony mutant is easily recognizable by its black pigmentation instead of the normal brown color of the wild type strains. This mutant is defective for the synthesis of β-alanyl derivatives such as N-β-alanyldopamine (NBAD) or N-β-alanylhistamine (carcinine), which are the products of the conjugation of β-alanine with dopamine or histamine respectively. Besides body color defect, other well-known features of this mutant are the neurological and behavioral disorders, such as abnormal electroretinograms, lacking ?on? and ?off? transients and abnormal circadian rhythm. We previously demonstrated that NBAD-synthase is an enzyme induced in epidermis with a narrow window of expression at the beginning of pupariation, the transition from pharate adult to imago, during the first hours after the ecdysis and in epidermal tissues of D. melanogaster embryos. We also found that this activity is also expressed constitutively in nervous system. The expression of Ebony in different brain regions suggests that this enzyme plays a role in the metabolism of histamine in visual system and in the metabolism of other neurotransmitters like dopamine, octopamine and serotonin. We previously analyzed the in vitro activity of NBAD-synthase in the ebony mutants e1 and e4 and we found that they are unable to synthesize β-alanyderivatives. We have also cloned and sequenced the e4 mutant gene, showing that it has a 447 base pairs deletion in its first exon, synthesizing a protein without activity. Despite being mutants for the same gene, some slight physiological differences exist among the different ebony mutants, with e4 being the less drastic phenotype. We characterized molecularly e1 and e11 to better understand their phenotypes. None of these 3 ebony mutants were able to synthesize NBAD. cDNA sequence analysis, showed that the nature of e1 defect is different from the previously sequenced e4. The e1 cDNA sequence from the beginning of the 3rd exon to the C-terminal region of the gene resulted impossible to amplified and cloned, suggesting that something complex such as an insertion or inversion may occur. The e11 sequence, surprisingly, was similar to that of e4, with the same deletion of 447 bp in the first exon.