The structural locus for a-amylase (AMY) in
Drosophila melanogaster is duplicated and divergently transcribed. These two genes are designated as
Amy-p and
Amy-d, respectively. We searched for the
cis-acting regulatory elements for full expression of the duplicated
Amy-p and
Amy-d loci, by injecting plasmid constructs containing sequences from the
Amy locus into preblastoderm embryos of an AMY-null strain and measuring exogenous AMY activity produced in transformed host larvae (i.e., the transient expression assay). Relative activities of endogenous amylase isozymes, AMY-1 and AMY-3, in extracts of AMY
1,3 larvae of a Canton-S are almost the same. However, three independently isolated
Amy-p1 constructs with only the 5' upstream regions of
Amy-p1 expressed a very low AMY-1 activity. Two other
Amy-p1 constructs with the 5' upstream region of
Amy-d3 in addition to that of
Amy-p1 produced a high activity. Thus, the 5' upstream region of
Amy-d3 is necessary for full expression of
Amy-p1. In order to locate
cis-regulatory elements within the 5' region of
Amy-d3, a series of hybrid constructs including this region were tested to locate them. Our results clearly show that the cis-acting regulatory sequences required for full expression of
Amy-p1 are located between the base pairs at -304 and -372 upstream of
Amy-d3 gene. In other words, only a short region located upstream of
Amy-d 3 was found to be necessary and sufficient for the full expression of
Amy-p1 in addition to its promoter. This region seems also necessary for the expression of
Amy-d 3.
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