The expression of esterase S gene of Drosophila virilis in Drosophila melanogaster

Birth and death of genes and functions in the beta-esterase cluster of Drosophila

Here we analyze the molecular evolution of the β-esterase gene cluster in the Drosophila genus using the recently released genome sequences of 12 Drosophila species. Molecular evolution in this small cluster is noteworthy because it contains contrasting examples of the types and stages of loss of gene function. Specifically, missing orthologs, pseudogenes, and null alleles are all inferred. Phylogenetic analyses also suggest a minimum of 9 gene gain–loss events; however, the exact number and age of these events is confounded by interparalog recombination. A previous enigma, in which allozyme loci were mapped to β-esterase genes that lacked catalytically essential amino acids, was resolved through the identification of neighbouring genes that contain the canonical catalytic residues and thus presumably encode the mapped allozymes. The originally identified genes are evolving with selective constraint, suggesting that they have a “noncatalytic” function. Curiously, 3 of the 4 paralogous β-esterase genes in the D. ananassae genome sequence have single inactivating (frame-shift or nonsense) mutations. To determine whether these putatively inactivating mutations were fixed, we sequenced other D. ananassae alleles of these four loci. We did not find any of the 3 inactivating mutations of the sequenced strain in 12 other strains; however, other inactivating mutations were observed in the same 3 genes. This is reminiscent of the high frequency of null alleles observed in one of the β-esterase genes (Est7/EstP) of D. melanogaster.

Complex organization of promoter and enhancer elements regulate the tissue- and developmental stage-specific expression of the Drosophila melanogaster Gld gene

The Drosophila melanogaster Gld gene has multiple and diverse developmental and physiological functions. We report herein that interactions among proximal promoter elements and a cluster of intronically located enhancers and silencers specify the complex regulation of Gld that underlies its diverse functions. Gld expression in nonreproductive tissues is largely determined by proximal promoter elements with the exception of the embryonic labium where Gld is activated by an enhancer within the first intron. A nuclear protein, GPAL, has been identified that binds the Gpal elements in the proximal promoter region. Regulation of Gld in the reproductive organs is particularly complex, involving interactions among the Gpal proximal promoter elements, a unique TATA box, three distinct enhancer types, and one or more silencer elements. The three somatic reproductive organ enhancers each activate expression in male and female pairs of reproductive organs. One of these pairs, the male ejaculatory duct and female oviduct, are known to be developmentally homologous. We report evidence that the other two pairs of organs are developmentally homologous as well. A comprehensive model to explain the full developmental regulation of Gld and its evolution is presented.

Male-predominant carboxylesterase expression in the reproductive system of molluscs and insects: immunochemical and biochemical similarity between Mytilus male associated polypeptide (MAP) and Drosophila sex-specific esterase S

We suggested that sexual differentiation of the reproductive system in gonochoric species of invertebrates can be characterized by common molecular mechanisms in spite of high morphological divergences of reproductive tract organs in different animal groups. The present study focused on this problem and report our observations on biochemical characteristics of male-associated polypeptide (MAP) identified in the gonad tissue of bivalve molluscs, Mytilus galloprovincialis, in comparison to those of male-specific carboxylesterase (esterase S) of Drosophila virilis ejaculatory bulbs. We provide evidences for the immunochemical similarity of Mytilus MAP and Drosophila esterase S. We also show that MAP is characterized by esterase activity toward both, alpha- and beta-naphthyl acetates. Using immunofluorescence, we found MAP in the gonad (mantle) connective tissue, membranes of follicles and around gonad ducts but not in sperm cells. Nevertheless, the levels of MAP expression depend on presence or absence of ripe spermatozoa in the gonad follicles. In mature gonads before spawning, MAP is expressed at high level, while in the spent gonads only traces of this polypeptide could be detected. Using Western immunoblot, MAP was not observed in spermatozoa obtained by biopsy of gonad follicles. In contrast, we found this protein in spawned sperm cells. Thus, we suggest that spawning may be required to establish the trafficking mechanisms that control whether MAP is retained or excreted by the gonad. Taken together, the results indicate that MAP of M. galloprovincialis is structurally and functionally related to esterase S of D. virilis ejaculatory bulbs.