Variation in the amount and activity of esterase 6 in a natural population of Drosophila melanogaster

Abstract

Forty-two homozygous lines each isoallelic for the Esterase 6 (Est-6) locus were extracted from a natural population of Drosophila melanogaster. Homogenates of 4-5 day old virgin adults of each sex from several replicate cultures of each line were assayed for EST6 activity. Depending on the line, males had from three to nine times more EST6 activity than females. Both sexes showed highly significant differences in EST6 activity among lines, with 32 and 27 fold differences between highest and lowest lines for males and females respectively. However, the variation in EST6 activity among lines was only weakly correlated across the two sexes. Female EST6 activity did not differ significantly across the six electrophoretic variants of EST6 found among the 42 lines. On the other hand, a significant proportion of the variation among lines in male EST6 activity could be explained by differences among the six electromorphs. However, most of these differences were due to the relatively high activities of males from two relatively rare electromorphs and there were no significant differences in male activity among the four more common EST6 electromorphs. Radial immunodiffusion assays with polyclonal anti-EST6 antibody established that differences among lines in male EST6 activity were largely due to differences in the number of EST6 protein molecules, with negligible differences in their specific activities. It is concluded that the natural population segregates for genetic variance with large effects on the amount of EST6 protein; that there is little overlap in the variance expressed in the two sexes; and that most of the variance is different from the polymorphisms for electrophoretically detectable variants of EST6.

The number and distribution of esterase 6 alleles in populations of Drosophila melanogaster

“…(1979) as modified by Game and Oakeshott (1989), except that the assay volume was scaled down to 210 iA and the reactions were carried out in microtitre plates and read in a Titertek® Multiskan Elisa plate reader. The thermostability of EST6 in each homogenate was expressed as the angular transform of the ratio of the mean activity of the two replicate treated 30 l aliquots to three times the mean activity of the two replicate untreated 10 pA aliquots.…”

Associations between restriction site polymorphism and enzyme activity variation for esterase 6 in Drosophila melanogaster.

“…The second measure, virgin adult male activity, comprises contributions from the same tissues as females but, in addition, includes high levels of EST6 activity in the anterior sperm ejaculatory duct (RICHMOND et al 1990). As a result, total male activity is from three to nine times higher than total female activity in the 42 lines studied here; threefold heritable differences occur among the lines for both measures, but the variation in the two sexes is largely independent (GAME and OAKESHOTT 1989).…”

“…The 42 lines have also been assayed for variation in EST6 activity (GAME and OAKESHOTT 1989). The activity in 4-5day-old virgins of each sex shows heritable threefold variation across the 42 lines.…”

Nucleotide polymorphism in the 5' promoter region of esterase 6 in Drosophila melanogaster and its relationship to enzyme activity variation.

“…The lines were extracted by COOKE et al (1987) from a natural population at Coffs Harbour in New South Wales and were derived from field-trapped males by a backcrossing program using the third chromosome balancer line TM3. The previously determined EST6 allozyme (COOKE et al 1987) and activity (GAME and OAKESHOTT 1989) phenotypes of the 17 lines appear in Figure 1.…”