A widely appreciated aspect of developmental robustness is pattern formation in proportion to size. But how such scaling features emerge dynamically remains poorly understood. Here we generate a data set of the expression profiles of six gap genes in Drosophila melanogaster embryos that differ significantly in size. Expression patterns exhibit size-dependent dynamics both spatially and temporally. We uncover a dynamic emergence of under-scaling in the posterior, accompanied by reduced expression levels of gap genes near the middle of large embryos. Simulation results show that a size-dependent Bicoid gradient input can lead to reduced Krüppel expression that can have long-range and dynamic effects on gap gene expression in the posterior. Thus, for emergence of scaled patterns, the entire embryo may be viewed as a single unified dynamic system where maternally derived size-dependent information interpreted locally can be propagated in space and time as governed by the dynamics of a gene regulatory network.

Fat storage is one of the important strategies employed in regulating energy homeostasis. Impaired lipid storage causes metabolic disorders in both mammals and Drosophila. In this study, we report CG9911, the Drosophila homolog of ERp44 (endoplasmic reticulum protein 44) plays a role in regulating adipose tissue fat storage. Using the CRISPR/Cas9 system, we generated a CG9911 mutant line deleting 5 bp of the coding sequence. The mutant flies exhibit phenotypes of lower bodyweight, fewer lipid droplets, reduced TAG level and increased expression of lipolysis related genes. The increased lipolysis phenotype is enhanced in the presence of ER stresses and suppressed by a reduction of the ER Ca2+. Moreover, loss of CG9911 per se results in a decrease of ER Ca2+ in the fat body. Together, our results reveal a novel function of CG9911 in promoting fat storage via regulating ER Ca2+ signal in Drosophila.

The ketogenic diet (KD) has been recognized as a potentially effective therapy to treat neuropsychiatric diseases, including epilepsy. Previous studies have indicated that KD treatment elevates γ-Amino butyric acid (GABA) levels in both human and murine brains, which presumably contributes to the KD's anti-seizure effects. However, this has not been systematically investigated at the synaptic level, and the underlying molecular mechanisms remain to be elucidated.

The Drosophila systemic immune response against many Gram-positive bacteria and fungi is mediated by the Toll pathway. How Toll-regulated effectors actually fulfill this role remains poorly understood as the known Toll-regulated antimicrobial peptide (AMP) genes are active only against filamentous fungi and not against Gram-positive bacteria or yeasts. Besides AMPs, two families of peptides secreted in response to infectious stimuli that activate the Toll pathway have been identified, namely Bomanins and peptides derived from a polyprotein precursor known as Baramicin A (BaraA). Unexpectedly, the deletion of a cluster of 10 Bomanins phenocopies the Toll mutant phenotype of susceptibility to infections. Here, we demonstrate that BaraA is required specifically in the host defense against Enterococcus faecalis and against the entomopathogenic fungus Metarhizium robertsii, albeit the fungal burden is not altered in BaraA mutants. BaraA protects the fly from the action of distinct toxins secreted by these Gram-positive and fungal pathogens, respectively, Enterocin V and Destruxin A. The injection of Destruxin A leads to the rapid paralysis of flies, whether wild type (WT) or mutant. However, a larger fraction of wild-type than BaraA flies recovers from paralysis within 5 to 10 h. BaraAs' function in protecting the host from the deleterious action of Destruxin is required in glial cells, highlighting a resilience role for the Toll pathway in the nervous system against microbial virulence factors. Thus, in complement to the current paradigm, innate immunity can cope effectively with the effects of toxins secreted by pathogens through the secretion of dedicated peptides, independently of xenobiotics detoxification pathways.

Animals adjust their lipid metabolism states in response to pathogens infection. However, the underlying molecular mechanisms for how lipid metabolism responds to infection remain to be elusive. In this study, we assessed the temporal changes of lipid metabolism profiles during infection by an integrated transcriptomics and lipidomics analysis. Ergosterol is identified to be required for proper host defense to pathogens. Notably, ergosterol level is increased in the hemolymph upon bacterial infection. We show that the increase of ergosterol level by food supplement or genetic depletion of Acsl, a long-chain fatty acid-CoA synthetase, promotes host survival against bacterial challenges. Together, our results suggest a critical role of lipid metabolism adaption in the process of host defense against invading pathogens.

TALEs (transcription activator-like effectors) are a family of natural transcriptional activators originally isolated from the plant pathogen of Xanthomonas spp. The DNA binding motif of TALEs can be re-designed in such way that they bind specific DNA sequences other than their original targets. Fusion of customized TALEs with an endonuclease, Fok I, generates artificial enzymes that are targeted to specific DNA sites for cutting, allowing gene specific modification of both animal and plant genomes. Previously, we reported the use of TALEN (transcription activator-like effector nuclease) for the highly specific and efficient modification of the two Drosophila loci yellow and CG9797. Here, we describe a detailed protocol for TALEN-mediated genomic modification in Drosophila, with the aim of providing a practical bench guide for the Drosophila research community.

Parkinson's disease (PD) is associated with progressive degeneration of dopaminergic (DA) neurons. We report for the first time that the Drosophila histone deacetylase 6 (dHDAC6) plays a critical role in the protection of DA neurons and the formation of alpha-synuclein inclusions by using a Drosophila PD model constructed by ectopic expression of human alpha-synuclein. Depletion of dHDAC6 significantly enhances the effects caused by ectopic expression of alpha-synuclein, namely, loss of DA neurons, retinal degeneration, and locomotor dysfunction. Expression of alpha-synuclein in the DA neurons leads to fewer inclusions in the brains of dHDAC6 mutant flies than in wild-type flies. Conversely, overexpression of dHDAC6 is able to suppress the alpha-synuclein-induced DA neuron loss and retinal degeneration and promote inclusion formation. Furthermore, mutation of dHDAC6 reinforces the accumulation of oligomers that are suggested to be a toxic form of alpha-synuclein. We propose that alpha-synuclein inclusion formation in the presence of dHDAC6 protects DA neurons from being damaged by oligomers, which may uncover a common mechanism for synucleinopathies.

Sterile alpha and HEAT/Armadillo motif-containing protein (SARM) is conserved in evolution and negatively regulates TRIF-dependent Toll signaling in mammals. The SARM protein from Litopenaeus vannamei and its Drosophila orthologue Ectoderm-expressed (Ect4) are also involved in immune defense against pathogen infection. However, the functional mechanism of the protective effect remains unclear. In this study, we show that Ect4 is essential for the viral load in flies after a Drosophila C virus (DCV) infection. Viral load is increased in Ect4 mutants resulting in higher mortality rates than wild-type. Overexpression of Ect4 leads to a suppression of virus replication and thus improves the survival rate of the animals. Ect4 is required for the viral induction of STAT-responsive genes, TotA and TotM. Furthermore, Ect4 interacts with Stat92E, affecting the tyrosine phosphorylation and nuclear translocation of Stat92E in S2 cells. Altogether, our study identifies the adaptor protein Ect4 of the Toll pathway contributes to resistance to viral infection and regulates JAK/STAT signaling pathway.

Post-translational modification by the small ubiquitin-related modifier (SUMO) is important for a variety of cellular and developmental processes. However, the precise mechanism(s) that connects sumoylation to specific developmental signaling pathways remains relatively less clear. Here, we show that Smt3 knockdown in Drosophila wing discs causes phenotypes resembling JNK gain of function, including ectopic apoptosis and apoptosis-induced compensatory growth. Smt3 depletion leads to an increased expression of JNK target genes Mmp1 and puckered. We show that, although knockdown of the homeodomain-interacting protein kinase (Hipk) suppresses Smt3 depletion-induced activation of JNK, Hipk overexpression synergistically enhances this type of JNK activation. We further demonstrate that Hipk is sumolylated in vivo, and its nuclear localization is dependent on the sumoylation pathway. Our results thus establish a mechanistic connection between the sumoylation pathway and the JNK pathway through the action of Hipk. We propose that the sumoylation-controlled balance between cytoplasmic and nuclear Hipk plays a crucial role in regulating JNK signaling.

Notch signaling is a highly conserved pathway in multi-cellular organisms ranging from flies to humans. It controls a variety of developmental processes by stimulating the expression of its target genes in a highly specific manner both spatially and temporally. The diversity, specificity and sensitivity of the Notch signaling output are regulated at distinct levels, particularly at the level of ligand-receptor interactions.

Age-dependent ectopic fat accumulation (EFA) in animals contributes to the progression of tissue aging and diseases such as obesity, diabetes, and cancer. However, the primary causes of age-dependent EFA remain largely elusive. Here, we characterize the occurrence of age-dependent EFA in Drosophila and identify HDAC6, a cytosolic histone deacetylase, as a suppressor of EFA. Loss of HDAC6 leads to significant age-dependent EFA, lipid composition imbalance, and reduced animal longevity on a high-fat diet. The EFA and longevity phenotypes are ameliorated by a reduction of the lipid-droplet-resident protein PLIN2. We show that HDAC6 is associated physically with the chaperone protein dHsc4/Hsc70 to maintain the proteostasis of PLIN2. These findings indicate that proteostasis collapse serves as an intrinsic cue to cause age-dependent EFA. Our study suggests that manipulation of proteostasis could be an alternative approach to the treatment of age-related metabolic diseases such as obesity and diabetes.