Biology subjects

Shi, Q.

Publications and source records attributed to Shi, Q..

At least 73 records · Page 4Linked to original sources

bioRxiv2023

Frizzled-9 activates YAP to rescue simulated microgravity induced osteoblasts dysfunction.

Long-term space flight will lead to bone loss and osteoblasts dysfunction. The underlying mechanism is still far to reveal. Frizzled-9 (Fzd9) is a Wnt receptor which is essential to osteoblasts differentiation and bone formation. Here we investigate whether Fzd9 plays a role in simulated microgravity (SMG) induced osteoblasts dysfunction. After 1-3 days of SMG, the osteogenic markers were decreased which accompanied the decline of Fzd9 expression. Fzd9 also decreased in the femur of the rats after 3 weeks of hindlimb unloading. Overexpression of Fzd9 will counteract SMG-induced osteoblasts dysfunction. However, Fzd9 overexpression did not affect SMG induced pGSK3{beta} and {beta}-catenin expression or sublocalization. Overexpression of Fzd9 regulates the phosphorylation of Akt and ERK, as well as induces F-actin polymerization to form the actin cap, presses the nuclei, and increases the nuclear pore size, which promotes nuclear translocation of YAP. Our study provides mechanistic insights into the role of Fzd9 triggers actin polymerization and activates mechano-transducer YAP to rescue SMG-mediated osteoblasts dysfunction and indicates Fzd9 as a potential target to restore osteoblast function in bone diseases and space flight.

cell biology↗

bioRxiv2023

Spatially aware self-representation learning for tissue structure characterization and spatial functional genes identification

Spatially resolved transcriptomics (SRT) enable the comprehensive characterization of transcriptomic profiles in the context of tissue microenvironments. Unveiling spatial transcriptional heterogeneity needs to effectively incorporate spatial information accounting for the substantial spatial correlation of expression measurements. Here, we develop a computational method, SpaSRL (spatially aware self-representation learning), which flexibly enhances and decodes spatial transcriptional signals to simultaneously achieve spatial domain detection and spatial functional genes identification. This novel tunable spatially aware strategy of SpaSRL not only balances spatial and transcriptional coherence for the two tasks, but also can transfer spatial correlation constraint between them based on a unified model. Additionally, this joint analysis by SpaSRL deciphers accurate and fine-grained tissue structures and ensures the effective extraction of biologically informative genes underlying spatial architecture. We verified the superiority of SpaSRL on spatial domain detection, spatial functional genes identification and data denoising using multiple SRT datasets obtained by different platforms and tissue sections. Our results illustrate SpaSRLs utility in flexible integration of spatial information and novel discovery of biological insights from spatial transcriptomic datasets.

bioinformatics↗

bioRxiv2023

Structure-dependent spontaneous calcium dynamics in cultured neuronal networks on microcontact-printed substrates

Microcontact printing (CP) is widely used in neuroscience research. However, CP yields reduced cell-substrate adhesion compared with directly coating cell adhesion molecules. Here, we demonstrate that the reduced cell-substrate adhesion caused by CP, high seeding density, and the local restriction would separately contribute to more aggregated (neurons closer to each other in separate clusters) neuronal networks. Calcium recordings revealed that more aggregated networks presented fewer spontaneous calcium activity patterns, and were more likely dominated by synchronized network-wide calcium oscillation (network bursts). First, on a uniform microcontact-printed substrate, densely seeded neurons were reaggregated into a Petri dish-wide network consisting of small clusters, of which the calcium dynamics were dominated by network bursts. Next, further analysis revealed this dominance was maintained since its appearance, and the initiation and propagation of bursts in the small-cluster network shared a similar mechanism with that of homogeneous networks. Then, sparsely seeded neurons formed several networks with different aggregation degrees, in which the less clustered ones presented abundant time-varying subnetwork burst patterns. Finally, by printing locally restricted patterns, highly clustered networks formed, where dominant network bursts reappeared. These findings demonstrate the existence of structure-dependent spontaneous calcium dynamics in cultured networks on microcontact-printed substrates, which provide important insights into designing cultured networks by using CP, and into deciphering the onset and evolution of network bursts in developmental nerve systems.

neuroscience↗

bioRxiv2023

An orally bioavailable 4-phenoxy-quinoline compound as a potent AURKB relocation blocker for cancer treatment

We investigated a novel 4-phenoxy-quinoline-based scaffold that mislocalizes the essential mitotic kinase, AURKB. Here, we evaluated the impact of halogen substitutions (F, Cl, Br, I) on this scaffold with respect to various drug parameters. Br-substituted LXY18 was found to be a potent and orally bioavailable disruptor of cell division, at sub-nanomolar concentrations. LXY18 prevents cytokinesis by blocking AURKB relocalization in mitosis and exhibits broad-spectrum antimitotic activity in vitro. With a favorable PK profile, it shows widespread tissue distribution including the blood-brain barrier penetrance and effective accumulation in tumor tissues. More importantly, it markedly suppresses tumor growth. The novel mode of action of LXY18 may eliminate some drawbacks of direct catalytic inhibition of AURKs. Successful development of LXY18 as a clinical candidate for cancer treatment could enable a new, less toxic means of antimitotic attack that avoids drug resistance mechanisms.

cancer biology↗

bioRxiv2022

Bidirectional epigenetic editing reveals hierarchies in gene regulation

CRISPR perturbations are valuable tools for studying the functional effects of the genome. However, existing methods are limited in their utility for studying noncoding elements and genetic interactions. Here, we develop a system for bidirectional epigenetic editing (CRISPRai), in which orthogonal activating (CRISPRa) and repressive (CRISPRi) perturbations are applied simultaneously to multiple loci the same cell. We developed dual-gRNA-capture single-cell Perturb-seq to study the established interaction between SPI1 and GATA1, two hemopoietic lineage transcription factors, and discovered novel context-specific regulation modes for co-regulated genes. Extending CRISPRai to noncoding elements, we addressed how multiple enhancers interact to modulate expression of a shared target gene, Interleukin-2, in T cells. We found that enhancer function was primarily additive and enabled fine-tuning of gene expression, yet a clear hierarchy existed among enhancers in strength of gene expression control. The promoter was dominant over most enhancers in controlling gene expression; however, a small subset of enhancers exhibited strong functional effects, or gatekeeper function, and could turn off the gene despite promoter activation. Integration of these functional data with histone ChIP-seq and TF motif enrichment suggests the existence of multiple modes of enhancer-mediated gene regulation. Our method, CRISPRai for bidirectional epigenetic editing, provides an approach for identifying novel genetic interactions that may be overlooked when studied without bidirectional perturbations and can be applied to both genes and noncoding elements.

genomics↗

bioRxiv2022

The investigation on metabolites, genes and open chromatins involved in colored leaves of Eucommia ulmoides 'Ziye'

Eucommia ulmoides Oliver Ziye has unique purple-red leaves, which contain a variety of flavonoids, so it has high ornamental and medicinal value. However, the categories of flavonoids and molecular mechanism of specific accumulation of flavonoids in Ziye leaves is still unclear. Here, differences in metabolic level, gene expression level, chromatin accessibility and cis-regulatory elements were compared between Ziye and Huazhong 1 with green leaf color by metabolome profiling, RNA-seq, and ATAC-seq. A total of 205 flavonoids were identified from these two varieties using ultraperformance liquid chromatography-mass spectrometry (UPLC-MS). The accumulation of most delphinidin, cyaniding, quercetin, myricetin, and isorhamnetin derivatives peaked in old leaves of Ziye. Single-molecule long-read sequencing indicated that genes in the phenylpropanoid biosynthesis and flavonoid biosynthetic pathway, as well as many transcription factors including MYB, ERF, and WRKY were highly expressed in Ziye leaves. ATAC-seq revealed the presence of cell preferentially enriched peaks, which annotated to 6114 genes. Analysis of the genomic regions preferentially accessible in each cell type identified hundreds of overrepresented TF-binding motifs, highlighting sets of TFs such as MYB, ERF, and WRKY that are probably important for color formation of Ziye cell. Interestingly, the TFs within each of these cell type-enriched sets also showed evidence of extensively co-regulating each other. Our work demonstrated how chromatin accessibility and TF expression level influenced the expression of flavonoid biosynthesis associated genes, resulted in flavonoids accumulation in Ziye leaf. Our results could lay a foundation for further studies of gene expression and functional genomics in E. ulmoides.

genetics↗

bioRxiv2022

Cardiac MAO-A inhibition protects against catecholamine-induced ventricular arrhythmias via enhanced diastolic calcium control

BackgroundPeople with clinical depression exhibit increased risk for cardiac arrhythmias that could be related to differences in catecholamine metabolism. Emerging studies have implicated a pathophysiologic role for monoamine oxidase (MAO-A), which catalyzes catecholamine metabolism in the heart. MAO-A is the pharmacological target of some classes of anti-depressants. Here, we investigated the relationship between MAO-A activity and arrhythmogenesis. Methods & ResultsTriNetX database analysis of adult patients with depression (n=11,533) revealed that MAO inhibitor (MAOI) treatment is associated with significantly lower risk of arrhythmias compared with selective serotonin reuptake inhibitor (SSRI) treatment (16.7% vs 18.6%, p=0.0002). To determine a mechanistic link between MAO activity and arrhythmia, we utilized a genetically modified mouse model with cardiomyocyte-specific MAO-A deficiency (cMAO-Adef). Compared with wild-type (WT) mice, cMAO-Adef mice had a significant reduction in the incidence (38.9% vs. 77.8%, p=0.0409) and duration (55.33 {+/-} 26.21s vs.163.1 {+/-} 56.38s, p=0.0360) of catecholamine stress-induced ventricular tachyarrhythmias (VT). Reduced VT risk and duration were associated with altered cardiomyocyte Ca2+ handling in the cMAO-Adef hearts, including a marked increase in Ca2+ reuptake rate, decreased diastolic Ca2+ levels, decreased SR Ca2+ load and reduced Ca2+ spark activity following catecholamine stimulation relative to WT. Further analysis of molecular mechanisms revealed that altered Ca2+ handling in the cMAO-Adef hearts was related to decreased catecholamine-induced phosphorylation of Ca2+/calmodulin-dependent kinase II (CaMKII) and ryanodine receptor 2 (RyR2), and increased phosphorylation of phospholamban (PLB). ConclusionsThese findings suggest that MAO-A inhibition in cardiomyocytes mitigates arrhythmogenesis via enhanced Ca2+ reuptake that lowers diastolic Ca2+ levels thereby diminishing arrhythmic triggers following catecholamine stimulation. Thus, cardiac MAO-A represents a potential target for antiarrhythmic therapy.

physiology↗

bioRxiv2022

Inflammatory bowel disease-associated gut commensals degrade components of the extracellular matrix

Extracellular matrix (ECM) remodeling has emerged as a key feature of inflammatory bowel disease (IBD), and ECM fragments have been proposed as markers of clinical disease severity. Recent studies report increased protease activity in the gut microbiota of IBD patients. Nonetheless, the relationship between gut microbiota and ECM remodeling has remained unexplored. We hypothesized that members of the human gut microbiome can degrade host ECM, and that bacteria-driven remodeling, in turn, can enhance colonic inflammation. Through a variety of in vitro assays, we first confirmed that multiple bacterial species found in the human gut are capable of degrading specific ECM components. Clinical stool samples obtained from ulcerative colitis patients also exhibited higher levels of proteolytic activity in vitro compared to those of their healthy counterparts. Furthermore, culture supernatants from bacteria species capable of degrading human ECM accelerated inflammation in a dextran sodium sulfate (DSS)-induced colitis. Finally, we identified several of the bacterial proteases and carbohydrate degrading enzymes (CAZymes) potentially responsible for ECM degradation in vitro. Some of these protease families and CAZymes were also found in increased abundance in a metagenomic cohort of IBD. These results demonstrate that some commensal bacteria in the gut are indeed capable of degrading components of human ECM in vitro and suggest this proteolytic activity may be involved in the progression of IBD. A better understanding of the relationship between nonpathogenic gut microbes, host ECM, and inflammation could be crucial to unravel some of the mechanisms underlying host-bacteria interactions in IBD and beyond.

microbiology↗

bioRxiv2022

Significance of two transmembrane ion gradients for human erythrocyte volume stabilization.

Functional completeness of erythrocytes depends on high deformability of these cells, that allows them to pass through narrow tissue capillaries. The erythrocytes high deformability is provided due to maintenance of discoid shape with an optimal cell surface area to volume ratio. This ratio can be maintained due to cell volume stabilization at a given cell surface area. We studied role of Na/K-ATPase and transmembrane Na+ and K+ gradients in human erythrocyte volume stabilization at non-selective increase in cell membrane permeability to cations by using mathematical simulation. The simulation took into account a contribution of glycolytic metabolites and adenine nucleotides to cytoplasm osmotic pressure in the cells. It was shown that in the presence of Na/K-ATPase activated by intracellular sodium ions and two oppositely directed gradients of Na+ and K+ ions in the cell, the volume of the erythrocyte deviates from the optimal value by no more than 10% with a change in the non-selective permeability of the cell membrane to cations from 50 to 200% of the normal value. The transport Na/K-ATPase, which sets the ratio of transmembrane fluxes of sodium and potassium ions equal to 3:2, provides the best stabilization of the erythrocyte volume exactly at a non-selective increase in the permeability of the cell membrane, when the permeability for sodium and potassium ions increases equally. Such increase in erythrocyte membrane permeability is caused by oxidation of the membrane components and by mechanical stress during circulation. In the case of only one transmembrane ion gradient (Na+), the cell loses the ability to stabilize the volume when the cell membrane is damaged. In this case even small variations of cell membrane permeability cause dramatic changes in the cell volume. Our results reveal that the presence of two oppositely directed transmembrane ion gradients (Na+ and K+) and the transport Na/K-ATPase activated by intracellular sodium are fundamentally important conditions for the stabilization of cellular volume in human erythrocytes.

systems biology↗

bioRxiv2022

Trophoblast glycoprotein is required for efficient synaptic vesicle exocytosis from retinal rod bipolar cells.

Rod bipolar cells (RBCs) faithfully transmit light-driven signals from rod photoreceptors in the outer retina to third order neurons in the inner retina. Recently, significant work has focused on the role of leucine-rich repeat (LRR) proteins in synaptic development and signal transduction at RBC synapses. We previously identified trophoblast glycoprotein (TPBG) as a novel transmembrane LRR protein localized to the dendrites and axon terminals of RBCs. We now examine the effects on RBC physiology and retinal processing of TPBG genetic knockout in mice using immunofluorescence and electrophysiological techniques. The scotopic electroretinogram showed a modest increase in the b-wave and a marked attenuation in oscillatory potentials in the TPBG knockout. No effect of TPBG knockout was observed on the RBC dendritic morphology, TRPM1 currents, or RBC excitability. Because scotopic oscillatory potentials primarily reflect RBC-driven rhythmic activity of the inner retina, we investigated the contribution of TPBG to downstream transmission from RBCs to third-order neurons. Using electron microscopy, we found shorter synaptic ribbons in TPBG knockout axon terminals in RBCs. Time-resolved capacitance measurements indicated that TPBG knockout reduces synaptic vesicle exocytosis and subsequent GABAergic reciprocal feedback without altering voltage-gated Ca2+ currents. Thus, TPBG is required for normal synaptic ribbon development and efficient neurotransmitter release from RBCs to downstream cells. Our results highlight a novel synaptic role for TPBG at RBC ribbon synapses and support further examination into the mechanisms by which TPBG regulates RBC physiology. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/501380v2_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@13d5916org.highwire.dtl.DTLVardef@a3c259org.highwire.dtl.DTLVardef@12c74e0org.highwire.dtl.DTLVardef@1ad43a8_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

Quantification of astrocytic synaptic pruning in hippocampus in response to in vitro Aβ oligomer incubation via colocalization analysis with C1q

Quantification of synaptic engulfment is an indirect measurement of synaptic pruning. Here, we provide a detailed protocol for the volumetric rendering of individual high-resolution astrocytes in the CA1 region of hippocampus in an in vitro slice model of Amyloid-beta (A{beta}) treatment. This includes free floating slice preparation, treatment with A{beta} oligomers, immunofluorescence, confocal imaging and analysis of individual astrocytes. We also provide a comprehensive analysis for 3D rendering of astrocytes and assessment of synaptic engulfment via "eat-me tag" C1q protein and synaptic marker PSD95. HighlightsO_LIMeasurement of synaptic engulfment in response to treatment with A{beta} peptide C_LIO_LIVolumetric reconstruction of high resolution individual astrocyte C_LIO_LIColocalization analysis of astrocyte and complementary "eat-me" protein C1q C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=193 SRC="FIGDIR/small/491159v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@17d70b6org.highwire.dtl.DTLVardef@72db3dorg.highwire.dtl.DTLVardef@97968aorg.highwire.dtl.DTLVardef@1c447b_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

Inducible lncRNA transgenic mice reveal continual role of HOTAIR in promoting breast cancer metastasis

HOTAIR is a 2.2 kb long noncoding RNA (lncRNA) whose dysregulation has been linked to oncogenesis, defects in pattern formation during early development, and irregularities during the process of epithelial-to-mesenchymal transition (EMT). However, the oncogenic transformation determined by HOTAIR in vivo and its impact on chromatin dynamics are incompletely understood. Here we generate a transgenic mouse model with doxycycline-inducible expression of human HOTAIR in the context of the MMTV-PyMT breast cancer-prone background to systematically interrogate the cellular mechanisms by which human HOTAIR lncRNA acts to promote breast cancer progression. We show that sustained high levels of HOTAIR over time increased breast metastatic capacity and invasiveness in breast cancer cells, promoting migration and subsequent metastasis to the lung. Subsequent withdrawal of HOTAIR overexpression reverted the metastatic phenotype, indicating oncogenic lncRNA addiction. Furthermore, HOTAIR overexpression altered both the cellular transcriptome and chromatin accessibility landscape of multiple metastasis-associated genes and promoted epithelial to mesenchymal transition. These alterations are abrogated within several cell cycles after HOTAIR expression is reverted to basal levels, indicating an erasable lncRNA-associated epigenetic memory. These results suggest that a continual role for HOTAIR in programming a metastatic gene regulatory program. Targeting HOTAIR lncRNA may potentially serve as a therapeutic strategy to ameliorate breast cancer progression.

cancer biology↗

bioRxiv2022

Genome-wide CRISPR screens of T cell exhaustion identify chromatin remodeling factors that limit T cell persistence

T cell exhaustion limits anti-tumor immunity, but the molecular determinants of this process remain poorly understood. Using a chronic antigen stimulation assay, we performed genome-wide CRISPR/Cas9 screens to systematically discover genetic regulators of T cell exhaustion, which identified an enrichment of epigenetic factors. In vivo CRISPR screens in murine and human tumor models demonstrated that perturbation of several epigenetic regulators, including members of the INO80 and BAF chromatin remodeling complexes, improved T cell persistence in tumors. In vivo paired CRISPR perturbation and single-cell RNA sequencing revealed distinct transcriptional roles of each complex and that depletion of canonical BAF complex members, including Arid1a, resulted in the maintenance of an effector program and downregulation of terminal exhaustion-related genes in tumor-infiltrating T cells. Finally, Arid1a-depletion limited the global acquisition of chromatin accessibility associated with T cell exhaustion and led to improved anti-tumor immunity after adoptive cell therapy. In summary, we provide a comprehensive atlas of the genetic regulators of T cell exhaustion and demonstrate that modulation of the epigenetic state of T cell exhaustion can improve T cell responses in cancer immunotherapy.

immunology↗

bioRxiv2022

Ultra-high-throughput microbial single-cell whole genome sequencing for genome-resolved metagenomics

Microbes exist widely in nature. However, less than 1% of the species of microorganisms have been discovered so far, and more than 99% of microorganisms still remain unknown, which is called microbial dark matter. Unravelling microbial dark matter is not only helpful for exploring the unknown microbial world, but also of great significance for human health research. Ever since a long time ago, due to technical limitations, the microbiome, to a great extent, is still a black box. The traditional population-based metagenomic analysis tools are without single microbial resolution and they are stretched when studying rare and unknown microbial species. Here, we use high-throughput microdroplet technology to achieve the whole genome amplification of microbial single-cell genomes in pico-litter sized microdroplets, and develop subsequent library preparation steps such as indexing of the genome, to achieve the development of ultra-high-throughput microbial single-cell whole genome sequencing for genome-resolved metagenomics, aiming to provide a powerful new weapon for exploring microbial dark matter and other microbiological studies.

microbiology↗

bioRxiv2022

LANTSA: Landmark-based transferable subspace analysis for single-cell and spatial transcriptomics

Single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics (ST) technologies provide new insights to understand tissue organization and biological function. Accurately capturing the relationships of samples (e.g., sequenced cells, spatial locations) will result in reliable and consistent outcomes in downstream analyses. However, this undertaking remains a challenge for large-volume or cross-platform datasets due to transcriptional heterogeneity and high computational demands. Here, we introduce landmark-based transferable subspace analysis (LANTSA) to solve such challenges for scRNA-seq and ST datasets. Specifically, LANTSA constructs a representation graph of samples for clustering and visualization based on a novel subspace model, which can learn a more accurate representation and is theoretically proven to be linearly proportional to data size in terms of the time consumption. Furthermore, LANTSA uses a dimensionality reduction technique as an integrative method to extract the discriminants underlying the representation structure, which enables label transfer from one (learning) dataset (i.e., scRNA-seq profiles) to the other (prediction) datasets (e.g., scRNA-seq or ST profiles), thus solving the massive-volume or cross-platform problem. We demonstrated the superiority of LANTSA to identify accurate data structures via clustering evaluation on benchmark datasets of various scRNA-seq protocols, 10x Visium, and Slide-seq ST platforms. Moreover, we confirmed the integration capability of LANTSA to transfer cell annotation on large-scale and cross-platform scRNA-seq datasets. Finally, we validated the effectiveness of LANTSA for the identification of multiple mouse brain areas as well as the spatial mapping of cell types within cortical layers by integrating scRNA-seq and ST data.

bioinformatics↗

bioRxiv2021

Systematic discovery of receptor-ligand biology by engineered cell entry and single-cell genomics

Cells communicate with each other via receptor-ligand interactions on the cell surface. Here we describe a technology for lentiviral-mediated cell entry by engineered receptor-ligand interaction (ENTER) to decode receptor specificity. Engineered lentiviral particles displaying specific ligands deliver fluorescent proteins into target cells upon cognate receptor-ligand interaction, without genome integration or transgene transcription. We optimize ENTER to decode interactions between T cell receptor (TCR)-MHC peptides, antibody-antigen, and other receptor-ligand pairs. We develop an effective presentation strategy to capture interactions between B cell receptor (BCR) and intracellular antigen epitopes. Single-cell readout of ENTER by RNA sequencing (ENTER-seq) enables multiplexed enumeration of TCR-antigen specificities, clonality, cell type, and cell states of individual T cells. ENTER-seq of patient blood samples after CMV infection reveals the viral epitopes that drive human effector memory T cell differentiation and inter-clonal phenotypic diversity that targets the same epitope. ENTER enables systematic discovery of receptor specificity, linkage to cell fates, and cell-specific delivery of gene or protein payloads. HIGHLIGHTSO_LIENTER displays ligands, deliver cargos, and records receptor specificity. C_LIO_LIENTER deorphanizes antigen recognition of TCR and BCR. C_LIO_LIENTER-seq maps TCR specificity, clonality and cell state in single cells. C_LIO_LIENTER-seq of patient sample decodes antiviral T cell memory. C_LI

genomics↗

bioRxiv2021

Cell transcriptomic atlas of the non-human primate Macaca fascicularis

Studying tissue composition and function in non-human primates (NHP) is crucial to understand the nature of our own species. Here, we present a large-scale single-cell and single-nucleus transcriptomic atlas encompassing over one million cells from 43 tissues from the adult NHP Macaca fascicularis. This dataset provides a vast, carefully annotated, resource to study a species phylogenetically close to humans. As proof of principle, we have reconstructed the cell-cell interaction networks driving Wnt signalling across the body, mapped the distribution of receptors and co-receptors for viruses causing human infectious diseases and intersected our data with human genetic disease orthologous coordinates to identify both expected and unexpected associations. Our Macaca fascicularis cell atlas constitutes an essential reference for future single-cell studies in human and NHP.

cell biology↗

bioRxiv2021

Two Liberibacter Effectors Combine to Suppress Critical Innate Immune Defenses and Facilitate Huanglongbing Pathogenesis in Citrus

Genome sequence analyses predicted the presence of effectors in the gram-negative Candidatus Liberibacter asiaticus (CLas) even without the presence of a classical type III secretion system. Since CLas is not culturable, it is not possible to perform traditional gene knockout experiments to determine the role of various effectors in Huanglongbing (HLB) pathogenesis. Therefore, we followed an alternative functional genomics approach to examine the role of the CLas effectors in HLB pathogenesis in general and more specifically in suppressing citrus innate immune response. Here, we focused on the CLas effectors, P235 and Effector 3, to perform the following studies. First, proteomic studies by LC-MS/MS were conducted to screen the putative interacting citrus protein partners of P235 and Effector 3 from the healthy and CLas-infected Hamlin extracts and the most probable candidates were identified based upon their high protein scores from LC-MS/MS. Second, a transgenic tobacco split GFP system was designed for in planta detection of the most probable citrus interacting protein partners of P235 and Effector 3. Third, in vitro and in planta studies were performed to show that each of two effectors interacts with and inhibits the functions of multiple citrus proteins belonging to the innate immune pathways. These inhibitory interactions led to a high level of reactive oxygen species (ROS), blocking of bactericidal lipid binding protein (LTP), and induction of premature programmed cell death (PCD), thereby supporting CLas infection and HLB pathogenesis. Finally, an LTP mimic was designed to sequester and block the CLas effector and to rescue the bactericidal activity of LTP.

plant biology↗