Dosage compensation and dietary glucose repression of larval amylase activity inDrosophila miranda

Abstract

The functional locus for alpha-amylase (Amy) in Drosophila miranda is in the evolutionarily new X2 chromosome. X2 evolved from an autosome in response to an ancestral autosome-Y translocation that gave rise to the "neo-Y" chromosome of this species. Y-linked Amy, if still present in the ancestrally translocated element, is unexpressed. Dosage compensation for amylase activity was examined in larvae of the S 204 strain. Since dietary glucose is known to repress Amy expression in Drosophila melanogaster, dosage compensation of amylase activity in male larvae of D. miranda was tested by rearing larvae of both sexes on yeast diets with or without a glucose supplement. The WT 10 strain of Drosophila persimilis, a sibling species in which Amy is autosomally linked, was used as a reference for tests of amylase activity differences between the sexes. On the diet with glucose, Amy expression was repressed in both WT 10 and S 204 larvae and male larvae of S 204 displayed dosage compensation for amylase activity. On the nonrepressing diet consisting of yeast alone, S 204 continued to display dosage compensation.

Evolution of the response patterns to dietary carbohydrates and the developmental differentiation of gene expression of ?-amylase in Drosophila

“…First, glucose repression is a wellconserved trait through the developmental stages, while starch induction is observed mainly at the larval stage. Amylase expression of D. miranda, D. persimilis, and D. virilis is previously reported to be repressed by dietary glucose at the larval and adult stages (Norman and Doane 1990;Magoulas et al 1993). Second, the degree of induction or repression differs among species since a significant species × medium interaction was found.…”

“…As for the changes, Powell et al (1980) found that midgut patterns of amylase expression are highly variable both within and between species of the obscura and willistoni groups. Other changes include acquisition of dosage compensation associated with the translocation of the Amy gene to a novel X 2 chromosome in D. miranda (Norman and Doane 1990) and developmental changes of the expression pattern found in D. ananassae (Da Lage and Cariou 1993).…”

X chromosomal regulation in flies: when less is more

“…But in addition, a Robertsonian translocation of an autosome (Muller C element) to the Y chromosome generated a neo-Y chromosome (Macknight 1939). The fusion event is thought to occur about 2 million years ago and the homologue pair is kept in the male cells (neo-X chromosome) (Norman and Doane 1990). After the fusion event, neo-Y chromosome had undergone extensive random degeneration, including retrotransposition, duplication and nonsense mutations but most loci are still intact (Bachtrog 2006).…”

Rhythmic oscillations of α-amylase protein and its enzymatic activity levels in Drosophila melanogaster (Diptera: Drosophilidae)

“…The regulation of -amylase in D. melanogaster is known largely in terms of differences between the expression of its activity in various strains of flies, and on various diets (Hickey & Benkel, 1982;Hickey et al, 1994;Yamate & Yamazaki, 1999). It has been shown that most strains usually express one or two amylase isoforms differing slightly in molecular mass and widely in their activity levels (Doane, 1967;Norman & Doane, 1990). The differences in the activity levels of various isoforms of the enzyme are thought to be mostly caused by differences in protein levels rather than catalytic efficiency, but that the latter does make some contribution (Yamate & Yamazaki, 1999).…”

“…The expression of this enzyme is strongly repressed by increased dietary glucose (Hickey & Benkel, 1982;Magoulas et al, 1992Magoulas et al, , 1993Thompson et al, 1992). The downregulation pertains to the rate of synthesis of the enzyme, since its mRNA level becomes altered, but the catalytic efficiency of individual enzyme molecules does not (Norman & Doane, 1990). Catalytic efficiency does vary somewhat between strains of D. melanogaster (Yamate & Yamazaki, 1999).…”