Molecular cloning of alpha-amylase genes from Drosophila melanogaster. I. Clone isolation by use of a mouse probe

Genetic Localization and Action of Regulatory Genes and Elements for Tissue-Specific Expression of alpha-Amylase in DROSOPHILA MELANOGASTER

Regulation of tissue-specific alpha-amylase (Amy) expression in Drosophila melanogaster was investigated with a newly developed method that detects the distribution of alpha-amylase allozymes in midguts of single adults or third-instar larvae. Trans regulation was found for alpha-amylase production in the posterior midgut (PMG) of adults, whereas cis regulation was demonstrated for the larval midgut. Independent regulation of components of the duplicated Amy locus was found in larvae. Recombination between the components of the Amy locus did not result in separation of the putative, very closely linked (less than 0.1 cM) cis-acting regulatory elements for alpha-amylase expression in the anterior midgut (AMG) of larvae. The expression of one of the components of the duplicated Amy locus in the AMG of larvae was influenced by a regulatory gene that was mapped at 2-79.1. alpha-Amylase expression in the adult PMG was controlled by a trans-acting regulatory gene localized at 2-79.0, in agreement with the data of Abraham and Doane.

Effect of nucleotide polymorphism in cis-regulatory and coding regions on amylase activity and fitness in Drosophila melanogaster

In natural populations of Drosophila melanogaster, there are many amylase (AMY) isozymes encoded by the duplicated genes, but their adaptive significance remains unclear. One approach to elucidate this issue is to understand the molecular basis of functional differences between the allelic classes. In this study, the effects of nucleotide polymorphism in 5'-flanking (cis-regulatory) and coding regions on AMY activity were examined, both on glucose and starch food media and in larvae and adults, using three chimeric Amylase (Amy) genes, Amy(c111), Amy(c161) and Amy(fc661). In this notation, the first number in the superscript indicates the sequence of the 5'-flnaking region (similar to Amy1 or Amy6), the second number refers to the coding region and the third number to the 3'-flanking region. We found that effect of nucleotide polymorphism in the coding region differed between larvae and adults. In larvae, the coding sequence of the Amy6 allele resulted in higher AMY activity than that of Amy1 allele, indicating the post-transcriptional differences between them. The cis-regulatory region derived from the Amy6 allele resulted in higher AMY activity in both larvae and adults. Thus, two fitness components, developmental time and productivity, were measured to examine whether polymorphism in the cis-regulatory region between the two alleles has an effect on them, but no significant difference was detected. We raise the implications for the evolution of subfunctionalization in multigene families.

Exploring the evolutionary history of the alcohol dehydrogenase gene (Adh) duplication in species of the family tephritidae

In the olive fruit fly Bactrocera oleae and the med fly Ceratitis capitata previous studies have shown the existence of two Adh genes in each species. This observation, in combination with the former finding that various Drosophila species of virilis and repleta group encode two isozymes of ADH which are the result of a gene duplication, challenged us to address a scenario dealing with the evolutionary history of the Adh gene duplication in Tephritidae. In our lab we proceeded to the cloning and sequence analysis of Adh genes from more tephritid species, a prerequisite for further study of this issue. Here we show that phylogenetic trees produced from either the nucleotide or the amino acid sequences of 14 tephritid Adh genes consisted of two main clusters, with Adh sequences of the same "type" grouping together (i.e., Adh1 sequences form a cluster and Adh2 sequences form a second one), as expected if there was one duplication event before speciation within the family Tephritidae. We used the amount of divergence between the two isozymic forms of Adh of the species carrying both Adh1 and Adh2 genes to obtain an estimate of the age of the duplication event. Interestingly, our data again support the hypothesis that the duplication of an ancestral Adh single gene in the family Tephritidae occurred before the emergence of the genera Bactrocera and Ceratitis, thus suggesting that Adh duplication was based on a prespeciation rather than a postspeciation event that might have involved two independent duplication events, one in each of the two genera.

The Amylase gene cluster on the evolving sex chromosomes of Drosophila miranda

On the basis of chromosomal homology, the Amylase gene cluster in Drosophila miranda must be located on the secondary sex chromosome pair, neo-X (X2) and neo-Y, but is autosomally inherited in all other Drosophila species. Genetic evidence indicates no active amylase on the neo-Y chromosome and the X2-chromosomal locus already shows dosage compensation. Several lines of evidence strongly suggest that the Amy gene cluster has been lost already from the evolving neo-Y chromosome. This finding shows that a relatively new neo-Y chromosome can start to lose genes and hence gradually lose homology with the neo-X. The X2-chromosomal Amy1 is intact and Amy2 contains a complete coding sequence, but has a deletion in the 3'-flanking region. Amy3 is structurally eroded and hampered by missing regulatory motifs. Functional analysis of the X2-chromosomal Amy1 and Amy2 regions from D. miranda in transgenic D. melanogaster flies reveals ectopic AMY1 expression. AMY1 shows the same electrophoretic mobility as the single amylase band in D. miranda, while ectopic AMY2 expression is characterized by a different mobility. Therefore, only the Amy1 gene of the resident Amy cluster remains functional and hence Amy1 is the dosage compensated gene.

Amyrel, a paralogous gene of the amylase gene family in Drosophila melanogaster and the Sophophora subgenus

We describe a gene from Drosophila melanogaster related to the alpha-amylase gene Amy. This gene, which exists as a single copy, was named Amyrel. It is strikingly divergent from Amy because the amino acid divergence is 40%. The coding sequence is interrupted by a short intron at position 655, which is unusual in amylase genes. Amyrel has also been cloned in Drosophila ananassae, Drosophila pseudoobscura, and Drosophila subobscura and is likely to be present throughout the Sophophora subgenus, but, to our knowledge, it has not been detected outside. Unexpectedly, there is a strong conservation of 5' and 3' flanking regions between Amyrel genes from different species, which is not the case for Amy and which suggests that selection acts on these regions. In contrast to the Amy genes, Amyrel is transcribed in larvae of D. melanogaster but not in adults. However, the protein has not been detected yet. Amyrel evolves about twice as fast as Amy in the several species studied. We suggest that this gene could result from a duplication of Amy followed by accelerated and selected divergence toward a new adaptation.

Distribution and evolution of introns in Drosophila amylase genes

While the two amylase genes of Drosophila melanogaster are intronless, the three genes of D. pseudoobscura harbor a short intron. This raises the question of the common structure of the Amy gene in Drosophila species. We have investigated the presence or absence of an intron in the amylase genes of 150 species of Drosophilids. Using polymerase chain reaction (PCR), we have amplified a region that surrounds the intron site reported in D. pseudoobscura and a few other species. The results revealed that most species contain an intron, with a variable size ranging from 50 to 750 bp, although the very majoritary size was around 60-80 bp. Several species belonging to different lineages were found to lack an intron. This loss of intervening sequence was likely due to evolutionarily independent and rather frequent events. Some other species had both types of genes: In the obscura group, and to a lesser extent in the ananassae subgroup, intronless copies had much diverged from intron-containing genes. Base composition of short introns was found to be variable and correlated with that of the surrounding exons, whereas long introns were all A-T rich. We have extended our study to non-Drosophilid insects. In species from other orders of Holometaboles, Lepidoptera and Hymenoptera, an intron was found at an identical position in the Amy gene, suggesting that the intron was ancestral.

Evolutionary relationships and sequence variation of alpha-amylase variants encoded by duplicated genes in the Amy locus of Drosophila melanogaster

To infer the genealogical relationships of alpha-amylase electromorphs of Drosophila melanogaster, we determined the nucleotide sequences of a collection of electromorphs sampled throughout the world. On average there were 1.0 amino acid substitutions between identical electromorphs and 3.9 between different electromorphs, respectively. We found that the evolution of AMY1 through AMY6 electromorphs occurred by sequential accumulation of single amino acid substitutions each causing one charge difference. The nucleotide diversities at synonymous sites within Amy1,Amy2,Amy3,Amy4 and Amy6 were 0.0321, 0.0000, 0.0355, 0.0059 and 0.0030, respectively. We also obtained evidence of genetic exchanges, such as intrachromosomal recombination, interchromosomal recombination or gene conversion, between the two duplicated Amy genes as well as among the alleles.

Molecular evolution of the duplicated Amy locus in the Drosophila melanogaster species subgroup: concerted evolution only in the coding region and an excess of nonsynonymous substitutions in speciation

From the analysis of restriction maps of the Amy region in eight sibling species belonging to the Drosophila melanogaster species subgroup, we herein show that the patterns of duplication of the Amy gene are almost the same in all species. This indicates that duplication occurred before speciation within this species subgroup. From the nucleotide sequence data, we show a strong within-species similarity between the duplicated loci in the Amy coding region. This is in contrast to a strong similarity in the 5' and 3' flanking regions within each locus (proximal or distal) throughout the species subgroup. This means that concerted evolution occurred only in the Amy coding region and that differentiated evolution between the duplication occurred in the flanking regions. Moreover, when comparing the species, we also found a significant excess of nonsynonymous substitutions. In particular, all the fixed substitutions specific to D. erecta were found to be nonsynonymous. We thus conclude that adaptive protein evolution occurred in the lineage of D. erecta that is a "specialist" species for host plants and probably also occurs in the process of speciation in general.

Molecular analysis of cis-regulatory sequences of the alpha-amylase gene in D. melanogaster: a short 5'-flanking region of Amy distal gene is required for full expression of Amy proximal gene

The structural locus for alpha-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 AMY1,3 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-d3 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-d3.

A short 5'-flanking region mediates glucose repression of amylase gene expression in Drosophila melanogaster

Expression of the alpha-amylase gene is highly repressed by dietary glucose in Drosophila melanogaster larvae. Here, we show that glucose repression is controlled by DNA sequences that are located upstream of the transcribed region. Recombinant gene constructions, in which the amylase promoter sequences were fused with the transcribed region of the Adh gene, were expressed in transgenic Drosophila larvae. The expression of ADH from the recombinant gene was shown to be subject to glucose repression. The function of potential regulatory cis-acting elements within the glucose responsive upstream region was examined by deletion analysis and by site-directed mutagenesis, coupled with expression assays in transformed larvae. The upstream deletion analysis showed that essential elements, both for overall activity and for glucose repression of the amylase gene, are located within a 109-bp region upstream of the transcription start site. Site-directed mutagenesis of these upstream sequences showed that the TATA motif, at position -31, and a novel 36-bp element, at position -109, were necessary for full activity of the amylase promoter. None of the introduced mutations resulted in loss of glucose responsiveness. These results indicate that glucose repression, in Drosophila, is mediated by transcriptional mechanisms that involve multiple, functionally redundant DNA elements.

The salivary glands of the vector mosquito, Aedes aegypti, express a novel member of the amylase gene family

Several cDNA clones with similarity to alpha-amylases have been characterized from a library made from adult female salivary gland RNA isolated from the vector mosquito, Aedes aegypti. The corresponding gene, designated Amylase I (Amy I), is expressed specifically in the proximal-lateral lobes of the adult female salivary gland, a pattern overlapping that of another gene, Mal I, involved in carbohydrate metabolism. The deduced amino acid sequence of Amy I indicates that this gene encodes a protein, approximate M(r) = 81,500, that appears to be a novel member of the amylase gene family. The mosquito protein contains a putative signal peptide for secretion and several consensus sites for asparagine-linked glycosylation. The Amy I protein shows significant similarity to invertebrate and vertebrate amylases including the conservation of four reactive and substrate binding sites. However, the amino-terminal region of the Amy-I protein is unique to the mosquito. Similarity with the Drosophila melanogaster protein is evident only after the first 260 amino acids in the mosquito sequence. The identification of this gene and its expression pattern adds to the observed relationship between spatial-specific gene expression in the female salivary glands and the specific feeding mode of the adult mosquito.

Molecular analysis of cis-regulatory sequences at the alpha-amylase locus in Drosophila melanogaster

The Amylase locus in Drosophila melanogaster contains duplicate, divergently transcribed structural genes for alpha-amylase, AmyA and AmyB. A sensitive and reliable transient expression assay was developed for testing amylase activities produced by exogenous Amy genes in somatically transformed larvae of an amylase-null strain of flies. Alleles tested, AmyA and AmyB, came from recombinant clone lambda Dm65, which contains genomic DNA from a Canton-S strain. The transient assay was used in a deletion analysis aimed at locating cis-regulatory sequences within the 5' region of AmyB. Results suggest that upstream regulatory sequences for correct spatial expression of AmyA and AmyB in third-instar larvae are located within 446 and 430 bp of their respective starts for transcription. A sequence required for high levels of AmyB expression was located within its 5' upstream region between the base pairs at -332 and -219. AmyA does not appear to have a comparable regulatory element in its 5'-flanking sequence. Barely detectable expression of AmyB was observed when it was flanked by only 92 bp of upstream sequence. A model is proposed for incomplete coordinate control of the duplicate Amy genes.

Tissue-specific and dietary control of alpha-amylase gene expression in the adult midgut of Drosophila melanogaster

The regulatory effects of allelic substitution at the trans-acting mapP locus and of dietary glucose on the expression of the duplicate genes for alpha-amylase (Amy) in Drosophila melanogaster were examined in the anterior midgut and posterior midgut regions of mature flies. The levels of amylase activity and amylase protein, as well as the abundance of amylase-specific RNA, were quantified. All 3 parameters of Amy expression were concordant. Results indicate that the effects of both mapP and dietary glucose are exerted at the level of amylase RNA. However, the tissue-specific effects of mapP are restricted to the posterior midgut and can therefore be distinguished from the effects of glucose in food medium, which influences amylase RNA levels in both the anterior and posterior midgut regions. Our data suggest that, in large part, strain-specific effects of dietary glucose can be explained on the basis of alternate alleles at the mapP locus in different homozygous strains of flies. Levels of amylase RNA in tissue extracts of flies from an amylase-null strain were also measured. Low levels were observed in both anterior and posterior midgut extracts. These were unresponsive to dietary conditions.

Multiple amylase genes in Drosophila ananassae and related species

The number and organization of amylase genes in Drosophila ananassae were investigated through classical genetic methods and in situ and filter hybridizations. At least four genes may be active in D. ananassae, organized as two independent pairs of closely linked copies on the 2L and 3L chromosomal arms. Several other species of the D. ananassae subgroup were studied and show the same chromosomal locations, suggesting an ancient duplication event. However, the number of Amy copies seems to be higher in the D. ananassae multigene family, and there is a striking intraspecific molecular differentiation.

The genetic structure of natural populations of Drosophila melanogaster. XXII. Comparative study of DNA polymorphisms in northern and southern natural populations

Restriction map variation in four gene regions (Adh, Amy, Pu and Gpdh) was surveyed for 86 second chromosomes from northern (Aomori) and southern (Ogasawara) Japanese populations of Drosophila melanogaster (43 chromosomes from each population). The regions examined cover a total of 62 kilobases. Estimates of nucleotide diversity (pi) were approximately constant across the gene regions and populations examined. The distribution of restriction site polymorphisms was compatible with the expectation from the neutral mutation-random genetic drift hypothesis, but insertion/deletion polymorphisms were not consistent with it. While the two populations shared a majority of restriction site polymorphisms, frequencies of individual restriction site variants were significantly different between the two populations at 7 out of 35 segregating sites. In addition, an insertion in the Amy region was found in 15 chromosomes from the Ogasawara sample but absent in the Aomori sample. A considerable difference was observed in the number of rare insertions and deletions between the two populations. The numbers of aberrations uniquely represented were 16 in the Ogasawara sample and only 3 in the Aomori sample. These findings suggest that the two populations were differentiated from each other to some degree by means of random genetic drift and/or other factors.

Molecular evolution of inversions in Drosophila pseudoobscura: the amylase gene region

The amylase region of the third chromosome of Drosophila pseudoobscura has been cloned and localized to cytological band 73A. It is contained within a series of highly polymorphic inversions and serves as a convenient tool for a molecular evolutionary analysis of the inverted gene arrangements. Amylase in D. pseudoobscura is a family of three genes, and some chromosomes have deletions for one or two of them. Two overlapping clones covering 26 kilobases were isolated and used as probes to survey DNA restriction map polymorphism among 28 lines, representing five of the major inversion types found in natural populations, as well as single chromosomes from the closely related species Drosophila persimilis and Drosophila miranda. Restriction-site differences are considerably greater among the various gene arrangements than among chromosomes with the same gene arrangement. Clustering the restriction map haplotypes yielded a dendrogram concordant with the phylogeny generated independently from cytogenetic considerations. The inversion polymorphism is estimated to be about 2 million years old.

DNA sequence evolution of the amylase multigene family in Drosophila pseudoobscura

The alpha-Amylase locus in Drosophila pseudoobscura is a multigene family of one, two or three copies on the third chromosome. The nucleotide sequences of the three Amylase genes from a single chromosome of D. pseudoobscura are presented. The three Amylase genes differ at about 0.5% of their nucleotides. Each gene has a putative intron of 71 (Amy1) or 81 (Amy2 and Amy3) bp. In contrast, Drosophila melanogaster Amylase genes do not have an intron. The functional Amy1 gene of D. pseudoobscura differs from the Amy-p1 gene of D. melanogaster at an estimated 13.3% of the 1482 nucleotides in the coding region. The estimated rate of synonymous substitutions is 0.398 +/- 0.043, and the estimated rate of nonsynonymous substitutions is 0.068 +/- 0.008. From the sequence data we infer that Amy2 and Amy3 are more closely related to each other than either is to Amy1. From the pattern of nucleotide substitutions we reason that there is selection against synonymous substitutions within the Amy1 sequence; that there is selection against nonsynonymous substitutions within the Amy2 sequence, or that Amy2 has recently undergone a gene conversion with Amy1; and that Amy3 is nonfunctional and subject to random genetic drift.

Restriction map and alpha-amylase activity variation among Drosophila mutation accumulation lines

The specific activities of alpha-amylase were measured for two sets of mutation accumulation lines, each set having originated from a different lethal-carrying second chromosome and SM1(Cy) chromosome and having been maintained by a balanced lethal system for about 300 generations. Significant variation was found to have accumulated among lines of both sets. Because of dysgenic crosses in the early generations of mutation accumulation, insertions or deletions of transposable elements in the Amy gene region were suspected of being the cause of this variation. In order to test this possibility, the structural changes in the 14 kb region of these chromosomes that includes the structural genes for alpha-amylase were investigated by restriction map analysis. We found that most part of the activity variation is due to replacements of a chromosomal region of SM1(Cy), including the structural genes for alpha-amylase, by the corresponding regions of the lethal chromosomes. One line also contained an insertion in this region but this line has an intermediate activity value. Thus, insertions of transposable elements into the Amy gene region were not found to be responsible for the new variation observed in alpha-amylase activity. If we remove those lines with structural changes from the analysis, the genetic variance of alpha-amylase specific activity among lines becomes non-significant in both sets of chromosomes.

Cloning and Expression of a Schwanniomyces occidentalis α-Amylase Gene in Saccharomyces cerevisiae

An α-amylase gene ( AMY ) was cloned from Schwanniomyces occidentalis CCRC 21164 into Saccharomyces cerevisiae AH22 by inserting Sau 3AI-generated DNA fragments into the Bam HI site of YEp16. The 5-kilobase insert was shown to direct the synthesis of α-amylase. After subclones containing various lengths of restricted fragments were screened, a 3.4-kilobase fragment of the donor strain DNA was found to be sufficient for α-amylase synthesis. The concentration of α-amylase in culture broth produced by the S. cerevisiae transformants was about 1.5 times higher than that of the gene donor strain. The secreted α-amylase was shown to be indistinguishable from that of Schwanniomyces occidentalis on the basis of molecular weight and enzyme properties.

Geographical polymorphism of amylase in Drosophila ananassae and its relatives

Strains of Drosophila ananassae from various places in the Tropics were investigated for their electrophoretical amylase pattern. Eleven isoamylases were found in adult flies. African populations were much more polymorphic than those from the Far East, and showed multibanded phenotypes, suggesting a multiplication of the Amy structural gene, with at least four copies per haploid genome in certain populations. Nine other species of the D. ananassae subgroup had weak amylase activity and only one or two variants were found in each species. D. monieri and D. varians are closely related to D. ananassae and showed a single band, similar to the isoamylase 3 of D. ananassae, which suggests that this might be an ancestral allele.

Polymorphism for the number of tandemly multiplicated glycerol-3-phosphate dehydrogenase genes in Drosophila melanogaster

A 26-kilobase-pair region encompassing the sn-glycerol-3-phosphate dehydrogenase (sn-glycerol-3-phosphate:NAD+ 2-oxidoreductase, EC 1.1.1.8) locus in Drosophila melanogaster from two natural populations in Japan was surveyed by restriction mapping. Both tandem duplications and triplications in this region were found in both populations. Detailed analysis of 86 chromosome 2 lines revealed restriction site and allozyme polymorphisms in the transcriptional unit: two restriction sites and the allozymes [fast (F) or slow (S)] were polymorphic among both duplication-bearing chromosomes and those carrying the standard sequence. This finding suggests recurrent recombination and/or gene conversion in this 5-kilobase-pair region. The differences observed for restriction site and allozyme haplotypes among the triplicated sequence both within and between populations, together with the distribution in natural populations, suggest a relatively recent ancestry of the triplication events and an independent origin in respective populations. Such events may represent the process of the formation of multigene families [compare Ohta, T. (1987) Genetics 115, 207-213]. Finally, the evolution of this type of polymorphism is discussed.

Molecular cloning of alpha-amylase genes from Drosophila melanogaster. III. An inversion at the Amy locus in an amylase-null strain

Overlapping clones of the structural gene region for alpha-amylase, Amy, were isolated from a lambda EMBL4 library containing genomic DNA fragments from an amylase-null strain of Drosophila melanogaster. Southern blot analysis and restriction endonuclease mapping of the cloned region indicate that it contains an Amy gene duplication within an inverted repeat sequence as is characteristic of the genomic arrangement for this species. Spacing between the cloned gene copies is similar to that commonly found in other strains. Evidence is presented for the presence of an inversion 4 to 9 kb in length within the cloned Amy region of the null strain. We postulate a causal relationship between the presence of the inversion and the failure of individuals from the null strain to express amylase. A model is proposed that suggests the inversion may have arisen through intramolecular (or sister-strand) recombination mediated by homologous pairing of the inverted repeat sequences at the Amy locus.

DNA rearrangement causes multiple changes in gene expression at the amylase locus in Drosophila melanogaster

A spontaneous null mutation at the alpha-amylase locus in Drosophila melanogaster was recovered from a laboratory population. The mutant strain was found to lack amylase enzyme production and to produce low, but detectable, levels of amylase mRNA. Moreover, the null strain is also lacking the glucose repression of amylase mRNA production which is seen in wild-type strains. The mutant phenotype correlates with a rearrangement in genomic DNA which, in turn, corresponds to a simple inversion in the arrangement observed most frequently in North American populations of D. melanogaster, including the common laboratory strain, Oregon-R. These results have implications for our understanding of both the evolution of the duplicated amylase gene structure and the regulation of amylase gene expression.

An amylase gene from Drosophila pseudoobscura is expressed in Escherichia coli. Functional selection and biochemical comparisons of the fly- and clone-produced amylases

An amylase gene from Drosophila pseudoobscura was isolated from a genomic library constructed in pBR322 and cloned in Escherichia coli by selecting for the ability of its product to hydrolyze starch, a carbon source not normally utilized by E. coli. Hybridization of pAMY17F to D. pseudoobscura polytene chromosomes shows a positive signal at the amylase pseudogene locus (bank 78, chromosome 3). The chimeric plasmid pAMY17F, has been altered in such a way as to increase amylase expression. Southern and Northern hybridizations to the cloned amylase DNA indicate that the source of the gene is from D. pseudoobscura. Biochemical properties such as pH optima, substrate specificities, electrophoretic analyses, inhibitor sensitivities, heat stabilities, temperature responsiveness and molecular weights indicate that the amylases produced by the fly and bacterial clone are similar and have similar properties. It appears that E. coli/pAMY17F is producing an amylase like that found in D. pseudoobscura.

Genetic and developmental characterization of the aldox-2 locus of Drosophila melanogaster

The aldox-2 locus in Drosophila melanogaster has been shown to affect differentially three molybdoenzymes, aldehyde oxidase, pyridoxal oxidase, and xanthine dehydrogenase. These effects are most obvious at times surrounding the pupal-adult boundary, when the normal organism accumulates large amounts of these enzymes in their active form. This locus has been more precisely mapped genetically to 2-82.9 +/- 2.1, with complete concordance between the effects of all recombinant chromosomes on all three enzymes. The cytogenetic location has also been determined to be between 52E and 54E8, with the likelihood that it lies within the region 54B1-54E8. The aldox-2 mutant allele has no visible phenotype and is completely recessive for enzyme effects at all stages tested. Segmental duplication of this region, including the aldox-2+ allele, has no apparent effect on the visible phenotype or the enzymatic activity. The mutant aldox-2 allele has no effect on the developmental expression of two unrelated enzymes, 6-phosphogluconate dehydrogenase and NADP+-dependent isocitrate dehydrogenase. The effects of this locus on aldehyde oxidase, xanthine dehydrogenase, and pyridoxal oxidase suggest that this locus may code for a product involved in the synthesis of the molybdenum cofactor common to these enzymes.

Separation of large DNA molecules by modified pulsed field gradient gel electrophoresis

Resolution of DNA fragments by pulsed field gradient gel electrophoresis is a function of the pulse time, geometry, and strength of the orthogonal electric fields. The first field geometry described had a number of disadvantages. We show that these disadvantages can be largely overcome by a modified electric field geometry together with an altered switch pattern. These changes are shown to have critical consequences for the technique. Resolution is more uniform across the gel, which permits more samples to be analyzed on the same gel. In addition, DNA molecules follow a migration path that is approximately straight down the gel. This aspect also increases the number of usable wells. One important property of the system described here provides some insight into the mechanism whereby DNA molecules are resolved by this method.

Structural organization of the Amy locus in seven strains of Drosophila melanogaster

Restriction maps were made by Southern blot analysis of the Amy (alpha-amylase) region in 7 strains of D. melanogaster using endonucleases SalI, XhoI and EcoRI. These were compared to the map of lambda Dm65 which contains the cloned Amy region. Strains used produce either two amylase variants, a single variant, or no amylase, yet all 7 strains carry two Amy genes as inverted repeats at the Amy locus. This and the orientation of the repeats resembles the situation in lambda Dm65. Most restriction sites mapped are conserved but two strains contain a large insertion which differs in size and position between strains. A complex anomaly, probably an inversion, exists at the Amy locus in a null strain. Maps for our Amy1,3 strain and the lambda Dm65 clone are identical, the DNA of each having been derived from a Canton-S wild stock. Restriction and genetic maps of the Amy region were aligned and alleles assigned to the proximal and distal genes, Amy-p and Amy-d.