The effect of distamycin A on heterochromatin condensation of Drosophila chromosomes

Larval neuroblasts of four species of Drosophila (melanogaster, hydei, virilis and funebris) were treated with distamycin A, a DNA ligand which induces distinct undercondensation in AT-rich heterochromatin. For each species the patterns of undercondensation were correlated with distribution of quinacrine-bright regions and of satellite DNAs. An overlapping of distamycin A-sensitive and quinacrine-bright heterochromatic regions was demonstrated for D. melanogaster and D. virilis, but not for D. hydei and D. funebris. Distamycin A undercondensation is thus a further criterion for resolving heterochromatin into different parts and enables identification of the steps of the condensation process within heterochromatic regions.     

Divergence in the neural control of oviposition in Drosophila

Of several species of Drosophila tested, only D. melanogaster was capable of ovipositing after decapitation. Two other species (D. tripunctata and D. pseudoobscura) were also capable of reflex oviposition during the operation but D. virilis and D. palustris were not. This divergence of neural control mechanisms suggests the existence of at least two alternate circuits for the control of insect oviposition.     

Evolution of single-copy DNA and the ADH gene in seven drosophilids

Summary Single-copy DNA was isolated fromDrosophila melanogaster and hybridized with total genomic DNA ofD. melanogaster, D. mauritiana, D. simulans, D. pseudoobscura, D. willistoni, D. hydei andD. virilis. The duplexes were thermally eluted from hydroxyapatite and the data used to assess the relatedness of each species toD. melanogaster. The general pattern of relatedness was similar to that predicted by morphological methods but with some notable exceptions. The rate of nucleotide substitution was estimated to be greater than 0.66% of bases per million years. An unexpected, rapidly evolving component ofD. melanogaster single-copy DNA was identified. The relatedness of these species was also studied with respect to the gene coding for alcohol dehydrogenase (ADH). The ADH gene, previously cloned fromD. melanogaster (Goldberg 1980), was hybridized with Southern blots of genomic digests of the seven species. The intensity and position of the hybridizing bands suggest the amount of divergence of the gene. Divergence was quantitated by reassociation of a fragment of the cloned ADH gene with total DNA of the seven drosophilids and thermal elution of the resultant duplexes from hydroxyapatite. The ADH gene was isolated from genomic clone libraries ofD. melanogaster, D. simulans andD. mauritiana and further studied by comparison of position of restriction sites. Species relationships deduced from comparison of total single-copy DNA and the ADH gene were consistent, demonstrating that a single gene can reflect divergence of the entire genome.     

A quantified ethogram for oviposition behavior and oviposition preference in the hemipterophagous butterfly Spalgis epius (Westwood) (Lepidoptera: Lycaenidae)

In this study, we examined the oviposition behavior and preference of Spalgis epius, a potential predator of mealybug crop pests. An ethogram of oviposition behavior was constructed based on observations made in an oviposition cage. Ovipositional behavioral acts were catalogued and separated into two behavioral repertoires: searching and egg laying. Gravid females of S. epius oviposited similar numbers of eggs on three mealybug species. Females preferred eggs and adults to nymphs of mealybugs for oviposition. Among three species of mealybugs attended by ants, females laid fewer eggs in the mealybug mass attended by Oecophylla smaragdina than on mealybugs attended by Tapinoma melanocephalum and Camponotus variegatus. Females preferred mealybug masses already containing conspecific eggs to mealybug masses containing conspecific larvae or Cryptolaemus montrouzieri larvae for egg deposition. Gravid females laid larger numbers of eggs under bright sunlight than in diffused sunlight or shade. The results of this study showed that S. epius can effectively attack any species of mealybugs, avoid intra- and interspecific competition, and co-exist with some species of ants attending mealybugs. With the knowledge of these behaviors, this predator can be effectively utilized as a major biological control agent of mealybugs.     

Rapid sequence divergence in a heat shock locus of Drosophila

In situ hybridization of cRNA transcribed from cloned D. melanogaster heat shock sequences to D. hydei chromosomes has shown that the D. hydei locus 2–32 A corresponds to the D. melanogaster locus 87 A/C and the D. hydei locus 2–36 A to the D. melanogaster locus 95 D, while the D. hydei locus 4–81 B corresponds to the D. melanogaster locus 63 BC. No hybridization to D. hydei chromosomes was found with cRNA transcribed from a clone containing the sequences encoded by the D. melanogaster locus 87 C. Neither D. melanogaster heat shock RNA nor D. virilis heat shock RNA hybridized significantly to the D. hydei heat shock locus 2–48 B. Furthermore, D. hydei heat shock RNA did not hybridize to the cytological homologs of locus 2–48 B found in D. repleta or in D. virilis. D, hydei heat shock. RNA did hybridize to the cytological homologs of locus 2–48 B in D. neohydei and D. eohydei, both of which belong to the hydei subgroup.     

椰子木蛾的产卵节律及其对寄主植物的产卵选择性

【背景】椰子木蛾是近年来新入侵我国棕榈科植物的害虫,研究其产卵习性可为监测和防治该虫提供参考。【方法】在室内条件下,观察、记录了椰子木蛾雌成虫的产卵节律及其对不同寄主植物的产卵选择性。【结果】椰子木蛾最高日产卵量可达34.4粒·头-1,且主要集中在羽化后4 d内产卵,占总产卵量的54.1%;产卵活动主要发生在夜间23:00到次日8:00;在椰子、蒲葵、大王棕、槟榔和散尾葵等寄主植物上的产卵量无显著差异,为89.3~147.7粒·头-1,但产卵位置存在差别。【结论与意义】椰子木蛾雌成虫具有较强的繁殖能力和产卵节律性,且在不同寄主植物上的产卵量一致。     

Genetics of esterases in Drosophila. III. Influence of different chromosomes on esterase pattern in Drosophila

The present report presents the results of starch and polyacrylamide gel electrophoretic studies of the influence of the X chromosome on the expression of esterase-6 in D. melanogaster × D. simulans hybrids heterozygous for locus Est-6 as well as studies of the influence of autosomes on esterase expression in Drosophila of the virilis group. A differential expression of esterase-6 has been detected in D. melanogaster × D. simulans hybrid males. A differential decrease in the activity of esterase-6 (both F and S allozymes) derived from D. melanogaster has been noted. In hybrid females, the activity of parental esterases is the same. It is suggested that the X chromosome regulates the expression of esterase-6 in D. melanogaster. Analysis of individuals obtained in different schemes of crosses between different species of Drosophila of the virilis group by use of stocks marked with mutations in various chromosomes indicates that other autosomes (in particular, autosomes 4 and 5) also influence the phenotypic expression of esterases (which are controlled by genes located on the second chromosome).     

OVIPOSITION SITE SELECTION BY DROSOPHILA MELANOGASTER AND DROSOPHILA SIMULANS

The effects of texture and larval residues in the medium on oviposition site selection (OSS) by Drosophila melanogaster and Drosophila simulans were studied. Drosophila melanogaster laid over 95% of its eggs in sieved medium (vs. unsieved medium); D. simulans laid all of its eggs in sieved medium. Surgical removal of antennal segments, and of fore-, mid-, or hindtarsi did not affect this result, indicating that sense organs involved in discriminating between sieved and unsieved medium are not confined to only one of the tested structures. In a “multiple choice” experiment, females were allowed to lay eggs in sieved medium of three types: unconditioned (fresh) medium, medium conditioned by D. melanogaster larvae (i.e., medium containing larval residues of D. melanogaster), and medium conditioned by D. simulans larvae. This choice experiment was performed with D. melanogaster and with D. simulans, using three densities of females (10, 20, and 40 per experimental unit). Both species laid more eggs in unconditioned medium than in either of the conditioned media, and density had no effect. D. melanogaster laid more eggs near the edges of food patches than in the center, whereas D. simulans showed no preference for edge or center. Under crowded conditions, both species survived at a higher rate in conditioned media (egg-to-adult survival) than in unconditioned medium, leading to the anomalous conclusion that females of these species seem not to maximize the survival of their offspring. This anomaly was partially resolved by the finding that medium already containing larvae gave lower survival rates than unoccupied medium.     

Aurora,a non-mobile retrotransposon in Drosophila melanogaster heterochromatin

A novel retrotransposon, aurora, containing 324 by long terminal repeats (LTRs) was detected in Drosophila melanogaster as a 5 kb insertion in the heterochromatic Stellate gene. This insertion causes a 5 bp duplication of the integration site. Southern analysis and in situ hybridization data show that all detectable copies of aurora are immobilized in the D. melanogaster heterochromatin. However, mobile copies of aurora were revealed in the cuchromatin of D. simulans. The element was also found in various species of the melanogaster subgroup and in the D. virilis genome.     

Reduced Fertility of Drosophila melanogaster Hybrid male rescue (Hmr) Mutant Females Is Partially Complemented by Hmr Orthologs From Sibling Species

The gene Hybrid male rescue (Hmr) causes lethality in interspecific hybrids between Drosophila melanogaster and its sibling species. Hmr has functionally diverged for this interspecific phenotype because lethality is caused specifically by D. melanogaster Hmr but not by D. simulans or D. mauritiana Hmr. Hmr was identified by the D. melanogaster partial loss-of-function allele Hmr¹, which suppresses hybrid lethality but has no apparent phenotype within pure-species D. melanogaster. Here we have investigated the possible function of Hmr in D. melanogaster females using stronger mutant alleles. Females homozygous for Hmr mutants have reduced viability posteclosion and significantly reduced fertility. We find that reduced fertility of Hmr mutants is caused by a reduction in the number of eggs laid as well as reduced zygotic viability. Cytological analysis reveals that ovarioles from Hmr mutant females express markers that distinguish various stages of wild-type oogenesis, but that developing egg chambers fail to migrate posteriorly. D. simulans and D. mauritiana Hmr⁺ partially complement the reduced fertility of a D. melanogaster Hmr mutation. This partial complementation contrasts with the complete functional divergence previously observed for the interspecific hybrid lethality phenotype. We also investigate here the molecular basis of hybrid rescue associated with a second D. melanogaster hybrid rescue allele, In(1)AB. We show that In(1)AB is mutant for Hmr function, likely due to a missense mutation in an evolutionarily conserved amino acid. Two independently discovered hybrid rescue mutations are therefore allelic.     

Comparison of dot chromosome sequences from D. melanogaster and D. virilis reveals an enrichment of DNA transposon sequences in heterochromatic domains

Background

Chromosome four of Drosophila melanogaster, known as the dot chromosome, is largely heterochromatic, as shown by immunofluorescent staining with antibodies to heterochromatin protein 1 (HP1) and histone H3K9me. In contrast, the absence of HP1 and H3K9me from the dot chromosome in D. virilis suggests that this region is euchromatic. D. virilis diverged from D. melanogaster 40 to 60 million years ago.

Results

Here we describe finished sequencing and analysis of 11 fosmids hybridizing to the dot chromosome of D. virilis (372,650 base-pairs) and seven fosmids from major euchromatic chromosome arms (273,110 base-pairs). Most genes from the dot chromosome of D. melanogaster remain on the dot chromosome in D. virilis, but many inversions have occurred. The dot chromosomes of both species are similar to the major chromosome arms in gene density and coding density, but the dot chromosome genes of both species have larger introns. The D. virilis dot chromosome fosmids have a high repeat density (22.8%), similar to homologous regions of D. melanogaster (26.5%). There are, however, major differences in the representation of repetitive elements. Remnants of DNA transposons make up only 6.3% of the D. virilis dot chromosome fosmids, but 18.4% of the homologous regions from D. melanogaster; DINE-1 and 1360 elements are particularly enriched in D. melanogaster. Euchromatic domains on the major chromosomes in both species have very few DNA transposons (less than 0.4 %).

Conclusion

Combining these results with recent findings about RNAi, we suggest that specific repetitive elements, as well as density, play a role in determining higher-order chromatin packaging.     

BrdU incorporation reveals DNA replication in non dividing glial cells in the larval abdominal CNS ofDrosophila

Glial cells are of significant importance for central nervous system development and function. In insects, knowledge of the types and development of CNS glia is rather low. This is especially true for postembryonic glial development. Using bromodeoxyuridine incorporation and enhancer trap lines we identified a reproducible spatial and temporal pattern of DNA replicating cells in the abdominal larval CNS (A3-7 neuromeres) ofDrosophila melanogaster. These cells correspond to embryonically established glial cells in that region. Except for a specific subfraction, these cells apparently do not divide during larval life. Similar patterns were found in two otherDrosophila species,D. virilis andD. hydei.     

Histone content in relation to amount of heterochromatin and developmental stage in three species of Drosophila

Relative amounts of various histone fractions in Drosophila chromatin were estimated densitometrically on electrophoretic gel separations. Several consistent and highly significant differences were obtained between larval and adult chromatin. The arginine-rich histones showed the most conspicuous changes: higher amounts of H4 in larvae, higher H3 in adults. The level of modification of these histones was clearly higher in larval than in adult chromatin. The modification of the two slower subfractions of H4 involved, in all probability, phosphorylation as well as acetylation. In all types of Drosophila chromatin studied 50% or more of the H2a molecules were phosphorylated—a remarkably high proportion. The species differences observed in relative amounts of histone were consistent in both stages of development. D. melanogaster differed from D. hydei and D. virilis in all histones except H2b, while the latter two species were generally similar. The interspecific variation in histone pattern was generally not correlated to differences in content of heterochromatin. The level of modification of H3 was, however, presumably an exception, as it was significantly lower for both larvae and adults in D. virilis than in the other two species. These differ from D. virilis in containing appreciably lower proportions of heterochromatic chromosome segments.     

A comparative investigation of the mating system of Drosophila hydei

Drosophila hydei mating system characteristics were studied and compared to what has been observed for two other Drosophila species. Hydei females will copulate when they are 3 days old, while males do not exhibit courtship behaviour until they are 9 days old. Unlike any other Drosophila, D. hydei females will re-mate as often as four times in one morning. However, re-mating in the same morning does not increase the number of progeny a female produces. Male D. hydei appear to deal with the continual receptivity of females and the pressures of sperm competition by passing less material to any given female but maintaining a constant level of fertility across numerous successive copulations. D. hydei is a cosmopolitan species which utilizes a wide variety of resources. As in D. melanogaster, another cosmopolitan species which is not closely related to it, male success appears to be dependent upon genetic quality only. This pattern differs from that observed in its relative D. mojavensis, a cactiphilic species endomic to the Sonoran desert, in which males contribute material benefits to females in their ejaculate.     

Protein metabolism of Drosophila male accessory glands—II: Species-specificity of secretion proteins

The male accessory gland proteins of six Drosophila species belonging to three subgenera are compared with respect to their one- and two-dimensional electrophoretic properties. The species are: D. melanogaster, D. busckii, D. funebris, D. hydei, D. nigromelanica and D. virilis. In addition, the enhancing effect of the gland's secretion on ovulation is examined in heterospecific secretion injection experiments. Clear-cut differences in the electrophoretic protein patterns of the six species are observed on native and dissociative gels. The patterns reveal that the species differ with regard to the occurrence of some protein fractions and the relative abundance of others. The heterospecific secretions fail to induce ovulation in D. melanogaster. The results thus provide unequivocal evidence that the male accessory gland products in Drosophila are highly species-specific.     

Regulation of Nadp-Malic Enzyme in the Eye-Antennal Disc of D. melanogaster/D. simulans Hybrids: Evidence for cis- and trans-Regulation

Pattern regulation of malic enzyme (ME) distribution in D. melanogaster/D. simulans (mel/sim) hybrid eye-antennal discs was investigated. Both cis- and trans-regulation of the spatial distribution pattern was observed within the eye portion of the disc complex. D. simulans possesses gene(s) that operate in trans in the hybrids to suppress ME staining along the morphogenetic furrow, a region that always stains in D. melanogaster. ME structural genes of both species were expressed in cis within the ommatidial preclusters and clusters of the hybrids. Malic enzyme was not expressed elsewhere in the eye disc of either species. Restoration of the D. melanogaster furrow pattern element occurred in partial hybrids that were homozygous for the D. melanogaster 3R where the structural gene resides. Therefore, a dominant gene(s) in the D. simulans 3R suppresses the D. melanogaster furrow pattern, while a recessive gene(s) in the D. melanogaster 3R restores the pattern when the trans-suppressor is removed. These conclusions agree with those found for regulation of aldehyde oxidase distribution in D. melanogaster/D. simulans hybrid wing discs.     

Oviposition of resistant and susceptible strains of Drosophila melanogaster in the presence of deltamethrin

Oviposition of three strains of Drosophila melanogaster in the presence of deltamethrin was observed. These strains had different levels of physiological susceptibility to deltamethrin. Two-choice tests were conducted with couples of flies in petri-dish arenas containing two oviposition dishes. On the first day of the experiment, females were given a choice between a treated oviposition dish and an untreated control dish. On the second day of the experiment, two control oviposition dishes were given to females. Although individual females showed a tendency to aggregate their eggs in one of the dishes, control experiments demonstrated an overall equal distribution of eggs between the dishes. When one of the two oviposition dishes in the arena was treated with deltamethrin, the percentage of females ovipositing and the mean number of eggs laid by females were reduced, compared with control arenas. Females avoided the treated oviposition dish and laid significantly more eggs on the control dish. Furthermore, when the deltamethrin concentration was increased on the first day, female flies postponed their oviposition and laid significantly more eggs on the second day. The resistant strain, SR, demonstrated the same capacity to select the untreated site for oviposition as the susceptible strain, but it showed a smaller oviposition reduction and egg retention. The relationship between physiological and behavioural susceptibility to deltamethrin is discussed.     

Differential Under-replication of Satellite DNAs during <Emphasis Type="Italic">Drosophila</Emphasis> Development

SATELLITE DNAs are heavily concentrated in the centromeric heterochromatin of metaphase chromosomes^1–3. Satellites and other repeated polynucleotide sequences are under-represented in the polytene, salivary gland cells of Drosophila melanogaster, D. virilis and D. hydei larvae but are fully represented in diploid cells from embryos and imaginal disks^4–6. This under-representation in polytene cells stems from the association of heterochromatin in the chromocentre and the progressive under-replication of the chromocentre during larval development^7,8.     

Gypsy homologous sequences inDrosophila subobscura (gypsyDS)

Summary Characterization of sequences homologous to theDrosophila melanogaster gypsy transposable element was carried out inDrosophila subobscura (gypsyDS). They were found to be widely distributed among natural populations of this species. From Southern blot and in situ analyses, these sequences appear to be mobile in this species.GypsyDS sequences are located in both euchromatic and heterochromatic regions. A completegypsyDS sequence was isolated from aD. subobscura genomic library, and a 1.3-kb fragment which aligns with the ORF2 of theD. melanogaster gypsy element was sequenced. Comparisons of this sequence in three species (D. subobscura, D. melanogaster, and D. virilis) indicate that there is greater similarity between theD. subobscura-D. virilis sequences than betweenD. subobscura andD. melanogaster. Molecular divergence ofgypsy sequences betweenD. virilis andD. subobscura is estimated at 16 MY, whereas the most likely divergence time of these two species is more than 60 MY. These data strongly suggest thatgypsy sequences have been horizontally transferred between these species.Offprint requests to: T.M. Alberola     

The hobo transposable element has transposase-dependent and-independent excision activity in drosophilid species

Mobility of the hobo transposable element was determined for several strains of Drosophila melanogaster and several Drosophila species. Mobility was assessed by use of an in vivo transient assay in the soma of developing embryos, which monitored hobo excision from injected indicator plasmids. Excision was detected in a D. melanogaster strain (cn; ry ⁴²) devoid of endogenous hobo elements only after co-injection of a helper plasmid containing functional hobo transposase under either heat shock or normal promoter regulation. Excision was also detected in D. melanogaster without helper in strains known to contain genomic copies of hobo. In Drosophila species confirmed not to contain hobo, hobo excision occurred at significant rates both in the presence and absence of co-injected helper plasmid. In four of the seven species tested, excision frequencies were two- to fivefold lower in the presence of plasmid-borne hobo. hobo excision donor sites were sequenced in indicator plasmids extracted from D. melanogaster cn; ry ⁴² and D. virilis embryos. In the presence of hobo transposase, the predominant excision sites were identical in both species, having breakpoints at the hobo termini with an inverted duplication of proximal insertion site DNA. However, in the absence of hobo transposase in D. virilis, excision breakpoints were apparently random and occurred distal to the hobo termini. The data indicate that hobo is capable of functioning in the soma during embryogenesis, and that its mobility is unrestricted in drosophilids. Furthermore, drosophilids not containing hobo are able to mobilize hobo, presumably by a hobo-related cross-mobilizing system. The cross-mobilizing system in D. virilis is not functionally identical to hobo with respect to excision sequence specificity.