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Huntington's disease is caused by an expansion of CAG repeats in exon 1 of the huntingtin gene encoding an extended PolyQ tract within the Huntingtin protein (mHtt). This expansion results in selective degeneration of striatal medium spiny projection neurons in the basal ganglia. The mutation causes abnormalities during neurodevelopment in human and mouse models. Here, we report that mHtt/PolyQ aggregates inhibit the cell cycle in the Drosophila brain during development. PolyQ aggregates disrupt the nuclear pore complexes of the cells preventing the translocation of cell cycle proteins such as Cyclin E, E2F and PCNA from cytoplasm to the nucleus, thus affecting cell cycle progression. PolyQ aggregates also disrupt the nuclear pore complex and nuclear import in mHtt expressing mammalian CAD neurons. PolyQ toxicity and cell cycle defects can be restored by enhancing RanGAP-mediated nuclear import, suggesting a potential therapeutic approach for this disease., Competing Interests: Madhu G Tapadia and Thomas E Lloyd reports financial support was provided by Department of Science and Technology (DST), New Delhi, Department of Biotechnology (DBT), New Delhi. 10.13039/100000002NIH grants R01NS094239 and R01AG068043 and the Packard Center for 10.13039/100018075ALS Research at 10.13039/100007880Johns Hopkins 10.13039/100008235School of Medicine. Madhu G Tapadia reports a relationship with Department of Science and Technology (DST), New Delhi and Department of Biotechnology (DBT) New Delhi that includes: funding grants. Thomas E Lloyd reports a relationship with 10.13039/100000002NIH grants R01NS094239 and R01AG068043 and the Packard Center for 10.13039/100018075ALS Research at 10.13039/100007880Johns Hopkins 10.13039/100008235School of Medicine that includes: funding grants. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 Published by Elsevier Ltd.)

Polyglutamine (polyQ) induced neurodegeneration is one of the leading causes of progressive neurodegenerative disorders characterized clinically by deteriorating movement defects, psychiatric disability, and dementia. Calcium [Ca 2+ ] homeostasis, which is essential for the functioning of neuronal cells, is disrupted under these pathological conditions. In this paper, we simulated Huntington's disease phenotype in the neuronal cells of the Drosophila eye and identified [Ca 2+ ] pump, sarco-endoplasmic reticulum calcium ATPase (SERCA), as one of the genetic modifiers of the neurodegenerative phenotype. This paper shows genetic and molecular interaction between polyglutamine (polyQ) aggregates, SERCA and DIAP1. We present evidence that polyQ aggregates interact with SERCA and alter its dynamics, resulting in a decrease in cytosolic [Ca 2+ ] and an increase in ER [Ca 2+ ], and thus toxicity. Downregulating SERCA lowers the enhanced calcium levels in the ER and rescues, morphological and functional defects caused due to expanded polyQ repeats. Cell proliferation markers such as Yorkie (Yki), Scalloped (Sd), and phosphatidylinositol 3 kinases/protein kinase B (PI3K/Akt), also respond to varying levels of calcium due to genetic manipulations, adding to the amelioration of degeneration. These results imply that neurodegeneration due to expanded polyQ repeats is sensitive to SERCA activity, and its manipulation can be an important step toward its therapeutic measures., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Huntington's disease occurs when the stretch of CAG repeats in exon 1 of the huntingtin ( htt ) gene crosses the permissible limit, causing the mutated protein (mHtt) to form insoluble aggregates or inclusion bodies. These aggregates are non-typically associated with various essential proteins in the cells, thus disrupting cellular homeostasis. The cells try to bring back normalcy by synthesizing evolutionary conserved cellular chaperones, and Hsp70 is one of the families of heat shock proteins that has a significant part in this, which comprises of heat-inducible and cognate forms. Here, we demonstrate that the heat shock cognate (Hsc70) isoform, Hsc70-4/HSPA8, has a distinct role in polyglutamate (PolyQ)-mediated pathogenicity, and its expression is enhanced in the polyQ conditions in Drosophila . Downregulation of hsc70-4 rescues PolyQ pathogenicity with a notable improvement in the ommatidia arrangement and near-normal restoration of optic neurons leading to improvement in phototaxis response. Reduced hsc70-4 also attenuates the augmented immune response by decreasing the expression of NF-κB and the antimicrobial peptides, along with that JNK overactivation is also restored. These lead to the rescue of the photoreceptor cells, indicating a decrease in the caspase activity, thus reverting the PolyQ pathogenicity. At the molecular level, we show the interaction between Hsc70-4, Polyglutamine aggregates, and NF-κB, which may be responsible for the dysregulation of signaling molecules in polyQ conditions. Thus, the present data provides a functional link between Hsc70-4 and NF-κB under polyQ conditions., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Rai and Tapadia.)

Background: Huntington's disease manifests due to abnormal CAG trinucleotide expansion, in the first exon of the Huntingtin gene and disease progression involves genetic, immune, and environmental components. The pathogenesis is characterized by the formation of Inclusion Bodies, disruption of neuronal circuitry, cellular machinery, and apoptosis, resulting in gradual and progressive loss of neuronal cells, ultimately leading to nervous system dysfunction. Thus, the present study was conducted to assess the effect of two Ayurvedic formulations, Guduchi and Madhuyashti, on Huntington's phenotype, using Drosophila as a model system., Method: The Huntington phenotype was ectopically induced in the Drosophila eye using the UAS-GAL4 binary system and the effect of the two Ayurvedic formulations were assessed by feeding the progenies on them. Degeneration was observed microscopically and Real Time-PCR was done to assay the alterations in the different transcripts of the innate immune pathways and JNK signaling pathway. Immunostaining was performed to assay different gene expression patterns., Result: The present study shows that Guduchi and Madhuyashti, endowed with immunomodulatory and intellect promoting properties, aggravates polyQ mediated neurodegeneration. We provide evidence that these formulations enhance JNK signaling by activating the MAP 3 K, dTAK1, which regulates the expression of Drosophila homologue for JNK. Sustained, rather than a transient expression of JNK leads to excessive production of Anti-Microbial Peptides without involving the canonical transcription factors of the Toll or IMD pathways, NF-κB. Enhanced JNK expression also increases caspase levels, with a concomitant reduction in cell proliferation, which may further contribute to increased degeneration., Conclusion: This is a report linking the functional relevance of Guduchi and Madhuyashti with molecular pathways, which can be important for understanding their use in therapeutic applications and holds promise for mechanistic insight into the mammalian counterpart., (© 2022. The Author(s).)

Background: Cells trigger caspase-mediated apoptosis to eliminate themselves from the system when tissue needs to be sculptured, or they detect any abnormality within them, thus preventing irreparable damage to the host. However, nonapoptotic activities of caspases are also involved in many cellular functions. Interestingly, Drosophila Malpighian tubules (MTs) express apoptotic proteins, without succumbing to cell death., Results: We show apoptosis-independent role of executioner caspase-3, Drice, in MT morphogenesis. Drice is required for precise cytoskeleton organization and convergent extension, failing which morphology, size, cell number, and arrangement get affected. Furthermore, characteristic stellate cell shape transformation in MTs is also governed by Drice. Genetic interaction study shows that Drice mediates its action by regulating Rho1GTPase functionally, and localization of polarity protein Disc large. Subsequently, downregulation of Rho1GTPase in Drice mutants significantly rescues the cystic MTs phenotype. The study shows a mechanism by which Drice governs tubulogenesis via Rho1GTPase-mediated coordinated organization of actin cytoskeleton and membrane stabilization., Conclusion: Collectively our findings suggest a nonapoptotic function of caspase-3 in fine-tuning of cellular rearrangement during tubule development, and these results will add to the growing understanding of diverse roles of caspases during its evolution in metazoans., (© 2021 American Association for Anatomy.)

Background: Adolescence is a distinctive stage of various changes and is noted as peak age for onset of many psychiatric disorders, especially linked to stress and depression. Several genetic variations are being increasingly known to be linked with stress and depression. The polymorphisms in two such genes, the BDNF and SLC1A3, have been reported to be linked with either depression/stress or with suicidal behaviour. These genes have not been validated in Indian population, and therefore there is a need to investigate these genes in Indian population. The present study was undertaken to test whether the known polymorphisms SLC1A3 C3590T, SLC1A3 C869G and BDNF G196A are associated or not with stress or depression in an eastern Indian population., Methods: A case-control association study was performed with 108 cases having variable levels of stress and depression and 205 matched controls. Detection of stress and depression was done by using standard instruments as PSS and CES-D, respectively and demographic profile was obtained for each individual on the basis of personal data sheet. Genotyping for the selected polymorphisms was performed by PCR followed by restriction digestion., Results: The SNP SLC1A3 C3590T was found to be associated with stress and depression (p = 0.0042, OR = 2.072). Therefore, the T allele increases the risk by more than two folds for stress and depression in the present population. The other allele of SLC1A3, G869C, as well as BDNF G196A were not associated with stress or depression in the population studied., Conclusion: SLC1A3 C3590T is a predisposition factor for stress and depression in an eastern Indian population, whereas SLC1A3 G869C and BDNF G196A were not found to be a risk factor. Therefore, presence of T allele of SLC1A3 C3590T, may predict the development of stress and depression in an individual. This may also help in the understanding of pathophysiology of the disease. However, these findings warrant a wider study in Indian populations and would be of significance in understanding the predisposition of stress and depression in this population.

Drosophila metamorphosis is associated with substantial metabolic activity involving cell death and cell proliferation leading to differentiation of adult tissues and structures. Unlike other larval tissues, Malpighian tubules (MTs) exhibit apoptotic immunity and do not undergo cell death but are carried over to the adult with some cell reorganisation. They persist despite the fact that they express apoptotic proteins and caspases. In the present study, we analysed the global transcription changes in MTs and compared with salivary glands, to decipher the biology of MTs. Gene set enrichment analysis indicated reduced expression of many ecdysone induced genes, including the critical regulator of cell death, E93 in MTs. We hypothesize that reduction of E93 could be because of over expression of ecdysone oxidase, which is high in MTs and is responsible for regulation of hormone titer by degradation of ecdysone. Ectopic expression of E93 in MTs results in cell death through autophagy. Fork head, which is crucial for survival, is enriched in the MT transcriptome, and its down regulation in MTs could be consequent to over expression of E93. Together our data suggests that the cascade of events initiated by ecdysone mediates survival of MTs through concerted action of multiple factors.

Stressors of different kinds adversely affect life history parameters like growth, development, and reproduction. Organisms overcome the negative impact of environmental stressors and strive to reach a tolerant state through genetic and metabolic activities. Ayurvedic formulations are reported to have life trait benefitting properties which improve capacity to withstand stress and tolerate adverse conditions. Guduchi (Tinospora cordifolia) and Madhuyashti (Glycirrhiza glabra) Ayurvedic formulations are known to have immunomodulatory, intellect promoting, and adaptogenic properties, thus favoring good health and healthy aging. Present study investigates the efficacy of Guduchi and Madhuyashti in providing tolerance to different stresses and the underlying mechanisms using the Drosophila model. Drosophila larvae/flies fed on Guduchi or Madhuyashti were better thermo-protected, which correlated with increased expression of heat shock genes even without the heat shock. Guduchi or Madhuyashti feeding also increased antimicrobial peptide expression, thus providing better tolerance to pathogenic assaults. Feeding on Guduchi- or Madhuyashti- supplemented food also enhanced starvation and desiccation tolerance. However, neither of these formulations provided beneficial effects when grown under crowded conditions or when exposed to oxidative stressors.

Formulations from the traditional Indian medicine, Ayurveda, have long been considered to have potent life-style enhancing effects, possibly by their effect(s) on key life-history attributes. Although several studies have reported beneficial effects of these formulations on different components of life history, few have investigated their concurrent influence on various life-history traits. Here, we report the results of an investigation showing the effect of two well-known Ayurvedic formulations, Guduchi and Madhuyashti , on fecundity and longevity of Drosophila melanogaster . Flies were either grown (i.e., larval exposure) and/or maintained (i.e., adult exposure) on standard food supplemented with 0.5% Guduchi or 0.5% Madhuyashti . It was observed that the longevity of adult flies of both sexes was not affected on feeding Guduchi food, but fecundity of the females was greatly enhanced. Fecundity was also found to be affected by the adult food and whether their mates were grown on Guduchi or normal food. Madhuyashti , on the other hand, significantly reduced mean longevity and had a stimulatory effect on female fecundity. This fecundity enhancing effect however seemed to be mediated through its effect on the males. Interestingly, much of these effects interacted with age in a complex way, making it difficult to generalize the overall effect of these formulations on the reproductive output of the flies. Ourstudy underlines the importance of evaluating the interacting effects of these (and similar) formulations on a range of life-history traits in a holistic way to understand their utility better.

Expansion of CAG repeats in certain genes has long been known to be associated with neurodegenerastion, but the quest to identity the underlying mechanisms is still on. Here, we analyzed the role of Yorkie, the coactivator of the Hippo pathway, and provide evidence to state that it is a robust genetic modifier of polyglutamine (PolyQ)-mediated neurodegeneration. Yorkie reduces the pathogenicity of inclusion bodies in the cell by activating cyclin E and bantam, rather than by preventing apoptosis through DIAP1. PolyQ aggregates inhibit Yorkie functioning at the protein, rather than the transcript level, and this is probably accomplished by the interaction between PolyQ and Yorkie. We show that PolyQ aggregates upregulate expression of antimicrobial peptides (AMPs) and Yorkie negatively regulates immune deficiency (IMD) and Toll pathways through relish and cactus, respectively, thus reducing AMPs and mitigating PolyQ affects. These studies strongly suggest a novel mechanism of suppression of PolyQ-mediated neurotoxicity by Yorkie through multiple channels.

The Malpighian tubules of insects are structurally simple but functionally important organs, and their integrity is important for the normal excretory process. They are functional analogs of human kidneys which are important physiological organs as they maintain water and electrolyte balance in the blood and simultaneously help the body to get rid of waste and toxic products after various metabolic activities. In addition, it receives early indications of insults to the body such as immune challenge and other toxic components and is essential for sustaining life. According to National Vital Statistics Reports 2016, renal dysfunction has been ranked as the ninth most abundant cause of death in the USA. This chapter provides detailed descriptions of Drosophila Malpighian tubule development, physiology, immune function and also presents evidences that Malpighian tubules can be used as a model organ system to address the fundamental questions in developmental and functional disorders of the kidney.

Background: Polyglutamine (polyQ) disorders are caused by expanded CAG (Glutamine) repeats in neurons in the brain. The expanded repeats are also expressed in the non-neuronal cells, however, their contribution to disease pathogenesis is not very well studied. In the present study, we have expressed a stretch of 127 Glutamine repeats in Malpighian tubules (MTs) of Drosophila melanogaster as these tissues do not undergo ecdysone induced histolysis during larval to pupal transition at metamorphosis., Results: Progressive degeneration, which is the hallmark of neurodegeneration is also observed in MTs. The mutant protein forms inclusion bodies in the nucleus resulting in expansion of the nucleus and affect chromatin organization which appear loose and open, eventually resulting in DNA fragmentation and blebbing. A virtual absence of tubule lumen was observed followed by functional abnormalities. As development progressed, severe abnormalities affecting pupal epithelial morphogenesis processes were observed resulting in complete lethality. Distribution of heterogeneous RNA binding protein (hnRNP), HRB87F, Wnt/wingless and JNK signaling and expression of Relish was also found to be affected. Expression of resistance genes following polyQ expression was up regulated., Conclusion: The present study gives an insight into the effects of polyQ aggregates in non-neuronal tissues., (Copyright © 2015. Published by Elsevier Inc.)

In insects, humoral response to injury is accomplished by the production of antimicrobial peptides (AMPs) which are secreted in the hemolymph to eliminate the pathogen. Drosophila Malpighian tubules (MTs), however, are unique immune organs that show constitutive expression of AMPs even in unchallenged conditions and the onset of immune response is developmental stage dependent. Earlier reports have shown ecdysone positively regulates immune response after pathogenic challenge however, a robust response requires prior potentiation by the hormone. Here we provide evidence to show that MTs do not require prior potentiation with ecdysone hormone for expression of AMPs and they respond to ecdysone very fast even without immune challenge, although the different AMPs Diptericin, Cecropin, Attacin, Drosocin show differential expression in response to ecdysone. We show that early gene Broad complex (BR-C) could be regulating the IMD pathway by activating Relish and physically interacting with it to activate AMPs expression. BR-C depletion from Malpighian tubules renders the flies susceptible to infection. We also show that in MTs ecdysone signaling is transduced by EcR-B1 and B2. In the absence of ecdysone signaling the IMD pathway associated genes are down regulated and activation and translocation of transcription factor Relish is also affected., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Malpighian tubules are the osmoregulatory and detoxifying organs of Drosophila and its proper development is critical for the survival of the organism. They are made up of two major cell types, the ectodermal principal cells and mesodermal stellate cells. The principal and stellate cells are structurally and physiologically distinct from each other, but coordinate together for production of isotonic fluid. Proper integration of these cells during the course of development is an important pre-requisite for the proper functioning of the tubules. We have conclusively determined an essential role of ecdysone hormone in the development and function of Malpighian tubules. Disruption of ecdysone signaling interferes with the organization of principal and stellate cells resulting in malformed tubules and early larval lethality. Abnormalities include reduction in the number of cells and the clustering of cells rather than their arrangement in characteristic wild type pattern. Organization of F-actin and β-tubulin also show aberrant distribution pattern. Malformed tubules show reduced uric acid deposition and altered expression of Na(+)/K(+)-ATPase pump. B2 isoform of ecdysone receptor is critical for the development of Malpighian tubules and is expressed from early stages of its development., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Joyousness or sadness is normal reaction to state of life. If any of these lead to certain semi-permanent changes in daily life, then it is termed as mental disorder. Depression is one of the mental disorders with a state of low mood and aversion to activities that exerts a negative effect on a person's thoughts and behaviour. Adolescent group is probably the world's largest active group of people, who are getting prone to this state of mind leading to their diminished mental and physical abilities. Depression is closely linked to stress and thus a chronic stressful life can increase the risk of depression. Depression is a complex disease having both genetic and environmental components as contributing factors. In this study an attempt has been made to put forward the understanding of the known genes and their functional relationships with depression and stress with special reference to BDNF and 5-HTTLPR. Analysis of common genetic variants associated with depression, especially in the members of a family who had a previous history, might help in identifying the individuals at risk prior to the onset of depression.

Systemic immune response via the Immune deficiency pathway requires Drosophila inhibitor of apoptosis protein 2 to activate the NF-κB transcription factor Relish. Malpighian tubules (MTs), simple epithelial tissue, are the primary excretory organs, performing additional role in providing protection to Drosophila against pathogenic infections. MTs hold a strategic position in Drosophila as one of the larval tissues that are carried over to adults, unlike other larval tissues that are histolysed during pupation. In this paper we show that Diap2 is an important regulator of local epithelial immune response in MTs and depletion of Diap2 from MTs, increases susceptibility of flies to infection. In the absence of Diap2, activation and translocation of Relish to the nucleus is abolished and as a consequence the production of IMD pathway dependent AMPs are reduced. Ion channels, (Na(+)/K(+))-ATPase and V-ATPase, are important for the immune response of MTs and expression of AMPs and the IMD pathway genes are impaired on inhibition of transporters, and they restrict the translocation of Relish into the nucleus. We show that Diap2 could be regulating ion channels, as loss of Diap2 consequently reduces the expression of ion channels and affects the balance of ion concentrations which results in reduced uric acid deposition. Thus Diap2 seems to be a key regulator of epithelial immune response in MTs, perhaps by modulating ion channels., (© 2013 Wiley Periodicals, Inc.)

Trinucleotide CAG repeat disorders are caused by expansion of polyglutamine (polyQ) domains in certain proteins leading to fatal neurodegenerative disorders and are characterized by accumulation of inclusion bodies in the neurons. Clearance of these inclusion bodies holds the key to improve the disease phenotypes, which affects basic cellular processes such as transcription, protein degradation and cell signaling. In the present study, we show that P-glycoprotein (P-gp), originally identified as a causative agent of multidrug-resistant cancer cells, plays an important role in ameliorating the disease phenotype. Using a Drosophila transgenic strain that expresses a stretch of 127 glutamine repeats, we demonstrate that enhancing P-gp levels reduces eye degeneration caused by expression of polyQ, whereas reducing it increases the severity of the disease. Increase in polyQ inclusion bodies represses the expression of mdr genes, suggesting a functional link between P-gp and polyQ. P-gp up-regulation restores the defects in the actin organization and precise array of the neuronal connections caused by inclusion bodies. β-Catenin homolog, Armadillo, also interacts with P-gp and regulates the accumulation of inclusion bodies. These results thus show that P-gp and polyQ interact with each other, and changing P-gp levels can directly affect neurodegeneration.

Malpighian tubules (MT) of Drosophila melanogaster are osmoregulatory organs that maintain the ionic balance and remove toxic substances from the body. Additionally they act as autonomous immune sensing organs, which secrete antimicrobial peptides in response to invading microbial pathogens. We show that the antimicrobial peptides (AMP) diptericin, cecropinA, drosocin and attacinA are constitutively expressed and are regulated in developmental stage specific manner. Their developmental expression begins from 3(rd) instar larval stage and an immune challenge increases the expression several folds. Spatial variations in the level of expression along the MT tissue are observed. The mortality of 3(rd) instar larvae fed on bacterial food is much less than that of the earlier larval stages, coinciding with the onset of innate immunity response in MT. Ectopic expression of AMP imparts better resistance to infection while, loss of function of one of the AMP through directed RNAi reduces host survival after immune challenge. The AMP secreted from the MT exhibit bactericidal activity. Expression of the NF-κB transcription factor, Relish, also coincides with activation of immune responsive genes in MT, demonstrating that immune regulation in MT is under developmental control and is governed by the Imd pathway.

Drosophila metamorphosis is characterized by the histolysis of larval structures by programmed cell death, which paves the way for the establishment of adult-specific structures under the influence of the steroid hormone ecdysone. Malpighian tubules function as an excretory system and are one of the larval structures that are not destroyed during metamorphosis and are carried over to adulthood. The pupal Malpighian tubules evade destruction in spite of expressing apoptotic proteins, Reaper, Hid, Grim, Dronc and Drice. Here we show that in the Malpighian tubules expression of apoptotic proteins commences right from embryonic development and continues throughout the larval stages. Overexpression of these proteins in the Malpighian tubules causes larval lethality resulting in malformed tubules. The number and regular organization of principal and stellate cells of Malpighian tubules is disturbed, in turn disrupting the physiological functioning of the tubules as well. Strikingly, the localization of beta-tubulin, F-actin and Disclarge (Dlg) is also disrupted. These results suggest that the apoptotic proteins could be having non-apoptotic function in the development of Malpighian tubules.

Drosophila development proceeds through three larval stages, before it pupates to reach adulthood. During pupation, larval tissues are destructed by programmed cell death and replaced by adult structures. Programmed cell death is a tightly regulated process accomplished by the induction of three closely linked pro-apoptotic genes reaper, hid and grim, ultimately leading to the activation of caspases, DRONC and DRICE and results in cell death. Unlike other larval tissues, Malpighian tubules are unique in not undergoing characteristic ecdysone-induced apoptosis and are carried to the adults. In this paper we show that apoptotic proteins, HID, GRIM, DRONC and DRICE are expressed in the Malpighian tubules, however they are sequestered in the nucleus. Significantly DRONC and DRICE are not enzymatically processed to active forms in the Malpighian tubules, however, ectopic expression of pro-apoptotic proteins leads to malformed Malpighian tubules and lethality. We also show that the Drosophila inhibitor of apoptotic protein 1, DIAP1, is localized and processed differently in Malpighian tubules. These results provide first evidence in favor of differential activity of apoptotic proteins in Malpighian tubules., (Copyright © 2010 Elsevier GmbH. All rights reserved.)

Drosophila development is a tightly regulated process involving metamorphosis of a relatively less mobile larva to a highly motile adult, triggered by secretion of 20-hydroxyecdysone. Under the influence of ecdysone, most of the larval tissues degenerate, while the imaginal cells differentiate and form adult specific structures. Although the larval Malpighian tubules do not seem to be affected by ecdysone during metamorphosis, we show that ecdysone signaling plays an important role in the early development and functioning of Malpighian tubules. Disruption of ecdysone receptor function, using targeted expression of dominant negative ecdysone receptor in stellate cells, results in disruption of organization of Malpighian tubules. The number of stellate cells is reduced in such Malpighian tubules. Further, they get clustered rather than distributed in their characteristic wild type pattern. We also demonstrate that expression of Drosophila integrin protein (DRIP), an aquaporin responsible for trans-cellular water transport, is also reduced in stellate cells when ecdysone signaling is disrupted. Our results show that of the three ecdysone receptor isoforms, only EcR-B2 rescues these phenotypes. A similar pattern of stellate cell clustering and reduced expression of DRIP is observed in ecd(1), a temperature sensitive mutant, under non-permissive conditions. These results suggest that ecdysone signaling is required for proper patterning and functioning of stellate cells and that EcR-B2 may be the primary isoform required for ecdysone signaling in stellate cells.

In situ expression of 2 multidrug resistance genes, mdr49 and mdr65, of Drosophila melanogaster was examined in wild-type third instar larval tissues under physiological conditions and after heat shock or colchicine feeding. Expression of these 2 genes was also examined in tumorous tissues of lethal (2) giant larvae I(2)gl4 mutant larvae. These 2 mdr genes show similar constitutive expression in different larval tissues under physiological conditions. However, they are induced differentially by endogenous (tumorous growth) and exogenous stresses (colchcine feeding or heat shock): whereas heat shock and colchicine feeding induce mdr49, tumorous condition is accompanied by enhanced expression of mdr49 and mdr65 genes.