Odor-guided behavior in Drosophila requires calreticulin

Two calcium-binding chaperones from the fat body of the Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) involved in diapause

Molecular chaperones are crucial for the correct folding of newly synthesized polypeptides, in particular, under stress conditions. Various studies have revealed the involvement of molecular chaperones, such as heat shock proteins, in diapause maintenance and starvation; however, the role of other chaperones in diapause and starvation relatively is unknown. In the current study, we identified two lectin-type chaperones with calcium affinity, a calreticulin (LdCrT) and a calnexin (LdCnX), that were present in the fat body of the Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) during diapause. Both proteins possessed an N-globular domain, a P-arm domain, and a highly charged C-terminal domain, while an additional transmembrane domain was present in LdCnX. Phylogenetic analysis revealed distinction at the order level. Both genes were expressed in multiple tissues in larval and adult stages, and constitutively throughout development, though a starvation response was detected only for LdCrT. In females, diapause-related expression analysis in the whole body revealed an upregulation of both genes by post-diapause, but a downregulation by diapause only for LdCrT. By contrast, males revealed no alteration in their diapause-related expression pattern in the entire body for both genes. Fat body-specific expression analysis of both genes in relation to diapause revealed the same expression pattern with no alteration in females and downregulation in males by post-diapause. This study suggests that calcium-binding chaperones play similar and possibly gender-specific roles during diapause.

Interpopulational Variations of Odorant-Binding Protein Expression in the Black Cutworm Moth, Agrotis ipsilon

Simple Summary

Odorant-binding proteins (OBPs) are small soluble transporter proteins that are believed to play a key role in insect olfaction. However, there is an emerging set of data that shows a role in insecticide resistance for similar families of binding proteins. The black cutworm Agrotis ipsilon is a migrant species of moth known to feed on multiple types of crops (polyphagous) worldwide. It is therefore likely that the olfactory system of this species can be modulated to adapt to different environments. We compared gene expression between American and European continental populations of the moth. We found continental-specific expression of antennal binding protein X (ABPX) and general odorant-binding protein 2 (GOBP2), suggesting a function of these proteins in migration, environment recognition, crop change and adaptation that are required for a polyphagous species such as A. ipsilon.

Abstract

A long-range migrant species of moth (Agrotis ipsilon) has served as a model to compare the expression profiles of antennal proteins between different continental populations. Our results showed that the American and French populations of the black cutworm moth, A. ipsilon, expressed the same odorant-binding proteins (OBPs), but apparently in different levels. Electrophoretic analysis of antennal protein profiles and reverse transcription polymerase chain reaction using RNA as a template showed significant differences between the two populations in the expression of antennal binding protein-X (ABPX) and general odorant-binding protein-2 (GOBP2). However, the two A. ipsilon populations showed no differences in RNA levels coding for pheromone binding proteins (PBPs), suggesting that the expression of generalist OBPs is population-specific and could be affected by specific odor and/or chemical changes in external environmental conditions. To support the role of ABPX and GOBP2 with expression, the role of ABPX and GOBP2 is discussed in regard to odor detection, memorization and/or degradation of toxic chemical insecticides.

A journey into the world of insect lipid metabolism

Lipid metabolism is fundamental to life. In insects, it is critical, during reproduction, flight, starvation, and diapause. The coordination center for insect lipid metabolism is the fat body, which is analogous to the vertebrate adipose tissue and liver. Fat body contains various different cell types; however, adipocytes and oenocytes are the primary cells related to lipid metabolism. Lipid metabolism starts with the hydrolysis of dietary lipids, absorption of lipid monomers, followed by lipid transport from midgut to the fat body, lipogenesis or lipolysis in the fat body, and lipid transport from fat body to other sites demanding energy. Lipid metabolism is under the control of hormones, transcription factors, secondary messengers and posttranscriptional modifications. Primarily, lipogenesis is under the control of insulin-like peptides that activate lipogenic transcription factors, such as sterol regulatory element-binding proteins, whereas lipolysis is coordinated by the adipokinetic hormone that activates lipolytic transcription factors, such as forkhead box class O and cAMP-response element-binding protein. Calcium is the primary-secondary messenger affecting lipid metabolism and has different outcomes depending on the site of lipogenesis or lipolysis. Phosphorylation is central to lipid metabolism and multiple phosphorylases are involved in lipid accumulation or hydrolysis. Although most of the knowledge of insect lipid metabolism comes from the studies on the model Drosophila; other insects, in particular those with obligatory or facultative diapause, also have great potential to study lipid metabolism. The use of these models would significantly improve our knowledge of insect lipid metabolism.

Microenvironmental Gene Expression Plasticity Among Individual Drosophila melanogaster

Differences in phenotype among genetically identical individuals exposed to the same environmental condition are often noted in genetic studies. Despite this commonplace observation, little is known about the causes of this variability, which has been termed microenvironmental plasticity. One possibility is that stochastic or technical sources of variance produce these differences. A second possibility is that this variation has a genetic component. We have explored gene expression robustness in the transcriptomes of 730 individual Drosophila melanogaster of 16 fixed genotypes, nine of which are infected with Wolbachia. Three replicates of flies were grown, controlling for food, day/night cycles, humidity, temperature, sex, mating status, social exposure, and circadian timing of RNA extraction. Despite the use of inbred genotypes, and carefully controlled experimental conditions, thousands of genes were differentially expressed, revealing a unique and dynamic transcriptional signature for each individual fly. We found that 23% of the transcriptome was differentially expressed among individuals, and that the variability in gene expression among individuals is influenced by genotype. This transcriptional variation originated from specific gene pathways, suggesting a plastic response to the microenvironment; but there was also evidence of gene expression differences due to stochastic fluctuations. These observations reveal previously unappreciated genetic sources of variability in gene expression among individuals, which has implications for complex trait genetics and precision medicine.

Infection with Plasmodium berghei ookinetes alters protein expression in the brain of Anopheles albimanus mosquitoes

Background

The behaviour of Anopheles spp. mosquitoes, vectors for Plasmodium parasites, plays a crucial role in the propagation of malaria to humans. Consequently, it is important to understand how the behaviour of these mosquitoes is influenced by the interaction between the brain and immunological status. The nervous system is intimately linked to the immune and endocrine systems. There is evidence that the malaria parasite alters the function of these systems upon infecting the mosquito. Although there is a complex molecular interplay between the Plasmodium parasite and Anopheles mosquito, little is known about the neuronal alteration triggered by the parasite invasion. The aim of this study was to analyse the modification of the proteomic profile in the An. albimanus brain during the early phase of the Plasmodium berghei invasion.

Results

At 24 hours of the P. berghei invasion, the mosquito brain showed an increase in the concentration of proteins involved in the cellular metabolic pathway, such as ATP synthase complex alpha and beta, malate dehydrogenase, alanine transaminase, enolase and vacuolar ATP synthase. There was also a rise in the levels of proteins with neuronal function, such as calreticulin, mitofilin and creatine kinase. Concomitantly, the parasite invasion repressed the expression of synapse-associated proteins, including enolyl CoA hydratase, HSP70 and ribosomal S60 proteins.

Conclusions

Identification of upregulated and downregulated protein expression in the mosquito brain 24 hours after Plasmodium invaded the insect midgut paves the way to better understanding the regulation of the neuro-endocrine-immune system in an insect model during parasite infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1830-9) contains supplementary material, which is available to authorized users.

De novo sequencing and transcriptome analysis of venom glands of endoparasitoid Aenasius arizonensis (Girault) (=Aenasius bambawalei Hayat) (Hymenoptera, Encyrtidae)

Aenasius bambawalei Hayat (Encyrtidae: Hymenoptera) has been synonymized with Aenasius arizonensis (Girault) is a small, newly discovered endoparasitoid of the cotton mealybug Phenacoccuss solenopsis Tinsley (Pseudococcidae: Hemiptera), which completes its life cycle inside the body of its host and it is a potential insect control tool. Despite the acquired knowledge regarding host-parasitoid interaction, little information is available on the factors of parasitoid origin able to modulate mealybug physiology. The components of A. arizonensis venom have not been well studied but venom from other parasitoids and wasps contain biologically active proteins that have potential applications in pest management or may be of medicinal importance. To provide an insight into the transcripts expressed in the venom gland of A. arizonensis, a transcriptomic database was developed utilizing high throughput RNA sequencing approaches to analyze the genes expressed in venom glands of this endoparasitic wasp. The resulting A. arizonensis RNA sequences were assembled de-novo with contigs then blasted against the NCBI non-redundant sequence database. Contigs which matched database sequences were mostly homologous to genes from hymenopteran parasitoids such as Nasonia vitripennis, Copidosoma floridanum, Fopius arsenus and Pteromalas puparium. Further analysis of the A. arizonensis database was then performed which focused on selected genes encoding proteins potentially involved in host developmental arrest, disrupting the host immune system, host paralysis, and transcripts that support these functions. Sequenced mRNAS predicted to encode full length ORFs of Calreticulin, Serine Protease Precursor and Arginine kinase proteins were identified and the tissue specific expression of these putative venom genes was analyzed by RT-PCR. In addition, results also demonstrate that de novo transcriptome assembly allows useful venom gene expression analysis in a species lacking a genome sequence database and may provide useful information for devising control tools for insect pests and other applications.

Inhibition of host cell encapsulation through inhibiting immune gene expression by the parasitic wasp venom calreticulin

Parasitoid wasps inject venom into the host to protect their offspring against host immune responses. In our previous study, we identified a calreticulin (CRT) in Pteromalus puparum venom. In this study, we expressed the wild-type and the coiled-coil domain deletion mutant P. puparum calreticulins (PpCRTs) in Escherichia coli and prepared polyclonal antibody in rabbit against PpCRT. Western blot analysis showed that PpCRT protein was not only present in the venom but also in all the tissues tested. Real time PCR results indicated that PpCRT mRNA was highly expressed in the venom gland. The transcript level of PpCRT in the venom gland was peaked at 2 days post-eclosion, while the PpCRT protein in the venom was maintained at a constant level. Both recombinant wild-type and mutant PpCRT proteins could bind to the surface of P. puparum eggs. Recombinant PpCRT inhibited hemocyte spreading and cellular encapsulation of the host Pieris rapae in vitro, and the coiled-coil domain is important for the inhibitory function of PpCRT. Immunocytochemistry results showed that PpCRT entered P. rapae hemocytes, and the coiled-coil domain played a role in this process. After injection of recombinant PpCRT into P. rapae pupae, real time PCR results showed that PpCRT inhibited transcript levels of host encapsulation-related genes, including calreticulin and scavenger receptor genes. In conclusion, our results suggest that P. puparum venom protects its offspring against host cellular immune responses via its functional component PpCRT to inhibit the expression of host cellular response-related genes.

Molecular cloning and functional study of calreticulin from a lepidopteran pest, Pieris rapae

Insects have an effective innate immune system to protect themselves from exogenous invaders. Calreticulin is a multifunctional protein mainly involved in directing proper conformation of proteins, controlling calcium level, and participating in immune responses. Previous suppression subtractive hybridization assay showed that the expression of Pieris rapae calreticulin (PrCRT) was suppressed after injection of Pteromalus puparum venom. In this study, we obtained a full length cDNA of PrCRT and expressed recombinant wild type and the N-domain deleted mutant PrCRT in bacteria. Real time quantitative PCR and western blot analyses showed that PrCRT mRNA and protein were expressed in hemocytes, Malpighian tubule, midgut, epidermis and fat body, with a higher level in hemocytes. PrCRT was probably located in endoplasmic reticulum distributing in the cytoplasm of hemocytes. Recombinant PrCRT was first able to attach and then enter the hemocytes by endocytosis. PrCRT mRNA in hemocytes was significantly induced after injection of yeast or beads, but did not change noticeably after injection of Escherichia coli or Micrococcus lysodeikticus. Recombinant PrCRT enhanced cellular encapsulation by P. rapae hemocytes in vitro, and the N-domain of PrCRT was required for encapsulation. RNAi of PrCRT by dsRNA injection impaired the ability of hemocytes to encapsulate beads. After parasitization by P. puparum, PrCRT mRNA and protein levels in P. rapae pupal hemocytes were significantly suppressed compared to non-parasitized control. Our results suggest that PrCRT is involved in cellular encapsulation and the pupal parasitoid P. puparum can decrease PrCRT expression to impair host cellular immune response.

Extensive epistasis for olfactory behaviour, sleep and waking activity in Drosophila melanogaster

Epistasis is an important feature of the genetic architecture of quantitative traits, but the dynamics of epistatic interactions in natural populations and the relationship between epistasis and pleiotropy remain poorly understood. Here, we studied the effects of epistatic modifiers that segregate in a wild-derived Drosophila melanogaster population on the mutational effects of P-element insertions in Semaphorin-5C (Sema-5c) and Calreticulin (Crc), pleiotropic genes that affect olfactory behaviour and startle behaviour and, in the case of Crc, sleep phenotypes. We introduced Canton-S B (CSB) third chromosomes with or without a P-element insertion at the Crc or Sema-5c locus in multiple wild-derived inbred lines of the Drosophila melanogaster Genetic Reference Panel (DGRP) and assessed the effects of epistasis on the olfactory response to benzaldehyde and, for Crc, also on sleep. In each case, we found substantial epistasis and significant variation in the magnitude of epistasis. The predominant direction of epistatic effects was to suppress the mutant phenotype. These observations support a previous study on startle behaviour using the same D. melanogaster chromosome substitution lines, which concluded that suppressing epistasis may buffer the effects of new mutations. However, epistatic effects are not correlated among the different phenotypes. Thus, suppressing epistasis appears to be a pervasive general feature of natural populations to protect against the effects of new mutations, but different epistatic interactions modulate different phenotypes affected by mutations at the same pleiotropic gene.

Evolutionary Genomics of Genes Involved in Olfactory Behavior in the Drosophila melanogaster Species Group

Previous comparative genomic studies of genes involved in olfactory behavior in Drosophila focused only on particular gene families such as odorant receptor and/or odorant binding proteins. However, olfactory behavior has a complex genetic architecture that is orchestrated by many interacting genes. In this paper, we present a comparative genomic study of olfactory behavior in Drosophila including an extended set of genes known to affect olfactory behavior. We took advantage of the recent burst of whole genome sequences and the development of powerful statistical tools to analyze genomic data and test evolutionary and functional hypotheses of olfactory genes in the six species of the Drosophila melanogaster species group for which whole genome sequences are available. Our study reveals widespread purifying selection and limited incidence of positive selection on olfactory genes. We show that the pace of evolution of olfactory genes is mostly independent of the life cycle stage, and of the number of life cycle stages, in which they participate in olfaction. However, we detected a relationship between evolutionary rates and the position that the gene products occupy in the olfactory system, genes occupying central positions tend to be more constrained than peripheral genes. Finally, we demonstrate that specialization to one host does not seem to be associated with bursts of adaptive evolution in olfactory genes in D. sechellia and D. erecta, the two specialists species analyzed, but rather different lineages have idiosyncratic evolutionary histories in which both historical and ecological factors have been involved.

Multiple measures of functionality exhibit progressive decline in a parallel, stochastic fashion in Drosophila Sod2 null mutants

Oxidative damage has been proposed as an important factor in the progression of pathological and non-pathological age-related functional declines. Here, we examine functional deterioration in short-lived flies mutant for the mitochondrial antioxidant Manganese Superoxide Dismutase (Sod2). We find that the decline of several functional measures of aging occurs, in an accelerated fashion, in Sod2 mutants. Olfactory behavior, locomotor ability and cardiac performance were all seen to decline rapidly in Sod2 mutants. On average, functional declines in Sod2 mutants occur in a pattern similar to that seen in late-life Drosophila with a normal complement of Sod2. In longitudinal experiments, however, we find that functional failures occur in every possible sequence in Sod2 mutants. Significantly, failure of these functional measures is not irreversible, as spontaneous functional recovery was sometimes observed. These findings support a model where ROS-related damage strikes at multiple organ systems in parallel, rather than a "chain of dominos" model, in which primary organ failure contributes to the deterioration of further organ systems.

A forward genetic screen in Drosophila implicates insulin signaling in age-related locomotor impairment

Age-related locomotor impairment (ARLI) is one of the most detrimental changes that occurs during aging. Elderly individuals with ARLI are at increased risks for falls, depression and a number of other co-morbidities. Despite its clinical significance, little is known about the genes that influence ARLI. We consequently performed a forward genetic screen to identify Drosophila strains with delayed ARLI using negative geotaxis as an index of locomotor function. One of the delayed ARLI strains recovered from the screen had a P-element insertion that decreased expression of the insulin signaling gene phosphoinositide-dependent kinase 1 (PDK1) Precise excision of the P-element insertion reverted PDK1 expression and ARLI to the same as control flies, indicating that disruption of PDK1 leads to delayed ARLI. Follow-up studies showed that additional loss of function mutations in PDK1 as well as loss of function alleles of two other insulin signaling genes, Dp110 and Akt (the genes for the catalytic subunit of phosphoinositide 3-kinase and AKT), also forestalled ARLI. Interestingly, only some of the strains with delayed ARLI had elevated resistance to paraquat, indicating that enhanced resistance to this oxidative stressor is not required for preservation of locomotor function across age. Our studies implicate insulin signaling as a key regulator of ARLI in Drosophila.

Quantitative genetic analysis of sleep in Drosophila melanogaster

Although intensively studied, the biological purpose of sleep is not known. To identify candidate genes affecting sleep, we assayed 136 isogenic P-element insertion lines of Drosophila melanogaster. Since sleep has been negatively correlated with energy reserves across taxa, we measured energy stores (whole-body protein, glycogen, and triglycerides) in these lines as well. Twenty-one insertions with known effects on physiology, development, and behavior affect 24-hr sleep time. Thirty-two candidate insertions significantly impact energy stores. Mutational genetic correlations among sleep parameters revealed that the genetic basis of the transition between sleep and waking states in males and females may be different. Furthermore, sleep bout number can be decoupled from waking activity in males, but not in females. Significant genetic correlations are present between sleep phenotypes and glycogen stores in males, while sleep phenotypes are correlated with triglycerides in females. Differences observed in male and female sleep behavior in flies may therefore be related to sex-specific differences in metabolic needs. Sleep thus emerges as a complex trait that exhibits extensive pleiotropy and sex specificity. The large mutational target that we observed implicates genes functioning in a variety of biological processes, suggesting that sleep may serve a number of different functions rather than a single purpose.

Phenotypic plasticity and genotype by environment interaction for olfactory behavior in Drosophila melanogaster

Genotype by environment interactions (GEI) play a major part in shaping the genetic architecture of quantitative traits and are confounding factors in genetic studies, for example, in attempts to associate genetic variation with disease susceptibility. It is generally not known what proportion of phenotypic variation is due to GEI and how many and which genes contribute to GEI. Behaviors are complex traits that mediate interactions with the environment and, thus, are ideally suited for studies of GEI. Olfactory behavior in Drosophila melanogaster presents an opportunity to systematically dissect GEI, since large numbers of genetically identical individuals can be reared under defined environmental conditions and the olfactory system of Drosophila and its behavioral response to odorants have been well characterized. We assessed variation in olfactory behavior in a population of 41 wild-derived inbred lines and asked to what extent different larval-rearing environments would influence adult olfactory behavior and whether GEI is a minor or major contributing source of phenotypic variation. We found that approximately 50% of phenotypic variation in adult olfactory behavior is attributable to GEI. In contrast, transcriptional analysis revealed that only 20 genes show GEI at the level of gene expression [false discovery rate (FDR) < 0.05], some of which are associated with physiological responses to environmental chemicals. Quantitative complementation tests with piggyBac-tagged mutants for 2 of these genes (CG9664 and Transferrin 1) demonstrate that genes that show transcriptional GEI are candidate genes for olfactory behavior and that GEI at the level of gene expression is correlated with GEI at the level of phenotype.

Reduced mitochondrial SOD displays mortality characteristics reminiscent of natural aging

Manganese superoxide dismutase (MnSOD or SOD2) is a key mitochondrial enzymatic antioxidant. Arguably the most striking phenotype associated with complete loss of SOD2 in flies and mice is shortened life span. To further explore the role of SOD2 in protecting animals from aging and age-associated pathology, we generated a unique collection of Drosophila mutants that progressively reduce SOD2 expression and function. Mitochondrial aconitase activity was substantially reduced in the Sod2 mutants, suggesting that SOD2 normally ensures the functional capacity of mitochondria. Flies with severe reductions in SOD2 expression exhibited accelerated senescence of olfactory behavior as well as precocious neurodegeneration and DNA strand breakage in neurons. Furthermore, life span was progressively shortened and age-dependent mortality was increased in conjunction with reduced SOD2 expression, while initial mortality and developmental viability were unaffected. Interestingly, life span and age-dependent mortality varied exponentially with SOD2 activity, indicating that there might normally be a surplus of this enzyme for protecting animals from premature death. Our data support a model in which disruption of the protective effects of SOD2 on mitochondria manifests as profound changes in behavioral and demographic aging as well as exacerbated age-related pathology in the nervous system.

Dietary restriction alters demographic but not behavioral aging in Drosophila

Dietary restriction extends lifespan substantially in numerous species including Drosophila. However, it is unclear whether dietary restriction in flies impacts age-related functional declines in conjunction with its effects on lifespan. Here, we address this issue by assessing the effect of dietary restriction on lifespan and behavioral senescence in two wild-type strains, in our standard white laboratory stock, and in short-lived flies with reduced expression of superoxide dismutase 2. As expected, dietary restriction extended lifespan in all of these strains. The effect of dietary restriction on lifespan varied with genetic background, ranging from 40 to 90% extension of median lifespan in the seven strains tested. Interestingly, despite its robust positive effects on lifespan, dietary restriction had no substantive effects on senescence of behavior in any of the strains in our studies. Our results suggest that dietary restriction does not have a global impact on aging in Drosophila and support the hypothesis that lifespan and behavioral senescence are not driven by identical mechanisms.

Dynamic genetic interactions determine odor-guided behavior in Drosophila melanogaster

Understanding the genetic architecture of complex traits requires identification of the underlying genes and characterization of gene-by-gene and genotype-by-environment interactions. Behaviors that mediate interactions between organisms and their environment are complex traits expected to be especially sensitive to environmental conditions. Previous studies on the olfactory avoidance response of Drosophila melanogaster showed that the genetic architecture of this model behavior depends on epistatic networks of pleiotropic genes. We performed a screen of 1339 co-isogenic p[GT1]-element insertion lines to identify novel genes that contribute to odor-guided behavior and identified 55 candidate genes with known p[GT1]-element insertion sites. Characterization of the expression profiles of 10 p[GT1]-element insertion lines showed that the effects of the transposon insertions are often dependent on developmental stage and that hypomorphic mutations in developmental genes can elicit profound adult behavioral deficits. We assessed epistasis among these genes by constructing all possible double heterozygotes and measuring avoidance responses under two stimulus conditions. We observed enhancer and suppressor effects among subsets of these P-element-tagged genes, and surprisingly, epistatic interactions shifted with changes in the concentration of the olfactory stimulus. Our results show that the manifestation of epistatic networks dynamically changes with alterations in the environment.

Endoplasmic Reticulum Stress Response of Bombyx Mori Calreticulin

We isolated a calreticulin cDNA from the silkworm, Bombyx mori. The cDNA encodes 398 amino acid residues of B. mori calreticulin, with an endoplasmic reticulum retentional HDEL motif at its C-terminus and a predicted molecular mass of 45,801 Da. The B. mori calreticulin shows high protein homology with calreticulin from G. mellonella (88%), A. aegypti (71%), D. melanogaster (69%) and H. sapiens (63%). The highest level of mRNA expression of B. mori calreticulin was exhibited in the fat body of this insect. Although expression of B. mori calreticulin was affected by disturbances in intracellular calcium levels, other ER stress conditions such as inhibition of intracellular protein transport, reduction of disulfide formation, glycosylation inhibition, heat shock and oxidative stress did not disrupt induction of B. mori calreticulin.

Functional senescence in Drosophila melanogaster

The fruit fly Drosophila melanogaster is one of the principal model organisms used for studying the biology of aging. Flies are well suited for such studies for a number of reasons. Flies develop to adulthood quickly, have a relatively short life span, and are inexpensive to house. Most of the fly genome has been sequenced, powerful genetic tools are available to manipulate it, and most fly genes have obvious homologues in mammals. While the majority of aging studies in flies have focused on regulation of life span, the fly is emerging as a powerful model system for investigating the biology that underlies age-related functional decline. Key to the use of flies in this way is the striking number of parallels between functional senescence in Drosophila and humans. Here, we review age-related functional declines in Drosophila, human correlates of these age-related declines, and common mechanisms that influence longevity and specific aspects of functional senescence in flies.

Delayed behavioural aging and altered mortality in Drosophila beta integrin mutants

The genetic basis for aging is being intensely investigated in a variety of model systems. Much of the focus in Drosophila has been on the molecular-genetic determinants of lifespan, whereas the molecular-genetic basis for age-related functional declines has been less vigorously explored. We evaluated behavioural aging and lifespan in flies harbouring loss-of-function mutations in myospheroid, the gene that encodes betaPS, a beta integrin. Integrins are adhesion molecules that regulate a number of cellular processes and developmental events. Their role in aging, however, has received limited attention. We report here that age-related declines in locomotor activity are ameliorated and that mean lifespan is increased in myospheroid mutants. The delayed functional senescence and altered mortality in myospheroid flies are independent of changes in body size, reproduction or stress resistance. Our data indicate that functional senescence and age-dependent mortality are influenced by beta integrins in Drosophila.