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Genome-wide examination of the transcriptional response to ecdysteroids 20-hydroxyecdysone and ponasterone A in Drosophila melanogaster

ABSTRACT: The 20-hydroxyecdysone (20E) hierarchy of gene activation serves as an attractive model system for studying the mode of steroid hormone regulated gene expression and development. Primary genes are activated by the direct action of the hormone and often code for proteins with regulatory function, some of which are responsible for the perpetuation of the response through the activation of secondary genes. Here we identify 35 primary 20E-response genes that are induced by 20E in the absence of protein synthesis in the embryonic cell line Kc167, and of those with known functions, most encode proteins with catalytic activity. Comparison of the genome-wide transcriptional response to 20E and to its plant derived structural analog ponasterone A (PoA) revealed a large difference in the transcriptional targets of these molecules. Despite the structural similarity of these two compounds, many more genes related to various aspects of development appear to be significantly induced by 20E than by PoA. Furthermore, we compared the 20E response in Kc cells to that of a natural 20E target tissue where the function of 20E has been well described, the salivary glands of wandering 3rd instar larvae, and found little overlap in 20E-responsive genes. Analysis of 20E-induced transcription of EcR, a known 20E-inducible gene and regulator of early and late 20E-responsive genes, reveals differences in the fold induction of EcR isoforms EcR-RA, ER-RC, and EcR-RD/E between Kc cells and salivary glands suggesting a possible cause for the observed differences in 20E-regulated gene transcription.

ORGANISM(S): Drosophila melanogaster

PROVIDER: GSE23928 | GEO | 2011/12/01

SECONDARY ACCESSION(S): PRJNA130325

REPOSITORIES: GEO

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Project description:Analysis of differential gene expression in third instar Drosophila salivary glands in the absence versus presence of cohesin. ABSTRACT: Developmental abnormalities observed in Cornelia de Lange Syndrome (CdLS) have been genetically linked to mutations in the cohesin machinery. These findings raise the possibility that cohesin, in addition to its canonical function of mediating sister chromatid cohesion, might also be involved in regulating gene expression. We report that cleavage of cohesinM-CM-^Us kleisin subunit in post-mitotic Drosophila salivary glands induces major changes (both up and down) in the transcript levels of many genes. Kinetic analyses of changes in transcript levels upon cohesin cleavage reveal that a subset of genes responds to cohesin cleavage within a few hours. In addition, cohesin binds to most of these loci, suggesting that cohesin is directly regulating their expression. Amongst these genes are several that are regulated by the steroid hormone Ecdysone. Transcripts at EcR and Eip74EF, which encode an Ecdysone Receptor and an Ecdysone-regulated transcription factor, respectively, decline ten-fold within four hours of cohesin cleavage. Cytological visualization of transcription at selected Ecdysone-responsive genes reveals that puffing at Eip74EF ceases within an hour or two of cohesin cleavage, long before any decline in EcR associated with this locus. We conclude that cohesin regulates expression of a distinct set of genes, including those mediating the Ecdysone response. A heat-inducible transgene (hs-TEV) was used to induce TEV in terminally differentiated third instar Drosophila salivary glands expressing either wild type (+ cohesin) or TEV-cleavable myc10-tagged Rad21 protein (Rad21TEV, - cohesin). Total RNA was isolated from + and - cohesin salivary glands 10-12 hours after heat shock induction of TEV (7 independent biological samples each). RNA samples were converted to cDNA, labeled with Cy3 and Cy5 respectively (3x) and vice versa (4x; dye swaps), and hybridized to INDAC FL003 arrays. Analysis of seven arrays, each hybridized to an independently generated sample-pair revealed major differences in transcript levels between + and - cohesin samples.

Project description:Juvenile hormone (JH) and 20-hydroxy-ecdysone (20E) are highly versatile hormones, coordinating development, growth, and reproduction in insects. Pulses of 20E provide key signals for initiating developmental and physiological transitions, while JH promotes or inhibits these signals in a stage-specific manner. Previous evidence suggests that JH and 20E might modulate innate immunity, but whether and how these hormones interact to regulate the immune response remains unclear. Here we show that JH and 20E have antagonistic effects on the expression of antimicrobial peptides (AMPs) in Drosophila melanogaster. In S2* cells challenged with bacterial peptidoglycans, 20E induces promoter activity and expression of AMPs in a dose-dependent manner, while JH III and its synthetic analogs (JHa) methoprene and pyriproxyfen abolish this 20E-dependent response. Using microarrays and GFP reporter gene assays in adult flies, we confirm that JH is a hormonal immuno-suppressor in vivo. When silencing both partners of the ecdysone receptor (EcR ) / ultraspiracle (USP) heterodimer with RNAi in S2* cells, 20E fails to activate Diptericin (Dpt) expression, suggesting that 20E regulates expression of this gene through EcR / USP signaling. In contrast, silencing methoprene-tolerant (MET), a candidate JH receptor, does not impair the immuno-suppressive action of JH III and JHa, indicating that in this context MET does not function as a JH receptor. Our results suggest that the balance of 20E and JH is a major determinant of immune homeostasis in insects. Experiment Overall Design: To examine the transcriptional response of y, w flies to treatment with exogenous JH, we performed a microarray experiment on females treated with JH or solvent (control). Flies were grown on regular yeast diet, switched to no-yeast food within one hour of eclosion, and yeast-starved for 5 days posteclosion to lower their endogenous JH titer and to synchronize their physiology (cf. Tu and Tatar, 2003; Gershman et al., 2007). Subsequently, we anesthetized flies on ice and topically treated them with 0.1 ïl of 187 mM JH III in acetone or with 0.1ï ïl 100% acetone (control) using a 1 ïl Hamilton syringe with a repeating dispenser. 12 hours after hormone administration, samples were snap-frozen in liquid nitrogen and stored at -80Â°C. RNA was isolated from samples (2 JH samples, 2 control samples, each with 30 females) by lysis, as described in Gershman et al. (2007). cDNA products were hybridized at the Brown University Genomics Core Facility to Affymetrix GeneChip Drosophila_1 Genome Arrays (2 replicate chips per treatment). The dataset consisted of 14,009 probe sets, with 6,142 probe sets annotated. Expression data were analyzed for significant over- or underrepresentation of gene ontology (GO) terms with the web application FatiGO (Al-Shahrour et al., 2004), using a two-fold change criterion. To test whether JH treatment significantly suppresses expression of AMPs we used t-tests implemented in JMP IN 5.1.

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Genome-wide examination of the transcriptional response to ecdysteroids 20-hydroxyecdysone and ponasterone A in Drosophila melanogaster

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