Biology subjects

Zhao, M.

Publications and source records attributed to Zhao, M..

At least 127 records · Page 7Linked to original sources

bioRxiv2024

Amd1-skp2 cascade regulates hepatocyte proliferation during liver growth and hepatocellular carcinoma development in zebrafish

Rapid hepatocyte proliferation is a common characteristic of liver growth in early liver development and hepatocellular carcinoma (HCC). Clarifying the mechanism how liver growth is regulated in development would benefit studying HCC progress. Although many genes have been reported to be involved in liver growth during early development, the mechanism underlying liver growth is far from being elucidated. Here we found that the liver undergoes rapid growth from 2dpf to 5dpf in zebrafish. Comparing the transcriptome for different staged hepatocytes identified 813 hepatocyte enriched genes at 3 dpf. Among them, S-adenosylmethionine decarboxylase proenzyme (AMD1) had not been previously reported to be involved in liver development. Our study further confirmed that amd1 was highly enriched in hepatocytes during liver rapid growth and that amd1 mutation inhibited liver growth mainly by repressing hepatocyte proliferation. Mechanistically, amd1 loss of function downregulated the expression of skp2, and skp2 is required for amd1 to regulate hepatocyte proliferation. Furthermore, the role of Amd1-Skp2 cascade in regulating hepatocyte proliferation was also conserved in a zebrafish HCC model. In conclusion, our study systematically identified some uncharacterized genes possibly being involved in regulating liver growth during zebrafish development, and revealed the role of amd1-skp2 cascade in regulating hepatocyte proliferation during liver growth and HCC progression. This work also provided a database which would benefit elucidating the mechanism how hepatocyte proliferation is regulated during liver growth and HCC progress.

developmental biology↗

bioRxiv2024

Spatiotemporal transcriptomic maps of mouse intracerebral hemorrhage at single-cell resolution

Intracerebral hemorrhage (ICH) is a severe and widespread disease that results in high mortality and morbidity. Despite significant advances made in clinical and preclinical research, the prognosis of ICH remains poor due to an incomplete understanding of the complex pathological responses. To address this challenge, we generated single-cell resolution spatiotemporal transcriptomic maps of mouse brain 1, 3, 7, 14, and 28 days after ICH. Our analysis revealed the cellular constituents and their dynamic responses following ICH. We found changes in gene expression that are indicative of active phagocytosis and lipid processing in the lesion core and identified genes associated with brain repair at the lesion border. Persistent lipid accumulation culminated in the phenotypic transition of macrophages into foam cells. Furthermore, our results demonstrate that ICH could stimulate neural stem cells in the subventricular zone, thereby enhancing neurogenesis in this niche. This study provides a spatiotemporal molecular atlas of mouse ICH that advances the understanding of both local and global responses of brain cells to ICH and offers a valuable resource that can aid the development of novel therapies for this devastating condition.

neuroscience↗

bioRxiv2024

CA1i pyramidal neurons mediate the role of NMDA receptor subunit GluN3A in depressive behavior and D-serine anti-depression

The hippocampus is a highly complex structure, defined by profound structural, functional, and molecular heterogeneity. The GluN3A subunit, which forms non-classic N-methyl-D-aspartate receptors (NMDARs), is enriched in the hippocampal CA1 subregion and has a poorly understood functional role, especially in stress-related behavioral regulation. Here, we employed chronic social defeat stress (CSDS) and GluN3A knockout (KO) mouse models combined with behavioral, molecular, genetic, pharmacological, and circuit-level analyses to investigate the role of hippocampal GluN3A in stress coping. We found that CSDS selectively reduced GluN3A expression in the intermediate CA1 (CA1i) region. Decreased GluN3A expression in CA1i, from either stress or genetic deletion, promoted passive coping behaviors, whereas overexpression of GluN3A in CA1i reversed the phenotype under both conditions. Mechanistically, consistent with GluN3A enrichment in pyramidal neurons, c-fos staining and fiber photometry revealed that GluN3A was essential for CA1i pyramidal neuronal activation during coping behaviors. Further chemogenetic manipulations demonstrated that activating CA1i neurons facilitated active coping, while inhibition induced passivity. Moreover, local administration of D-serine, an agonist of GluN3A-containing NMDARs, rapidly shifted coping behavior from passive to active by activating CA1i neurons via GluN3A-dependent mechanisms. Circuit tracing revealed that CA1i neurons project to multiple sub-hippocampal and cortico-limbic regions, and GluN3A overexpression selectively enhanced downstream neuronal activity in CA3 and infralimbic cortex, but not in the nucleus accumbens. Together, these findings identify GluN3A as a key molecule linking hippocampal subregional specialization with adaptive stress coping, and suggest that the rapid, resilience-promoting effects of D-serine are also GluN3A-dependent.

neuroscience↗

bioRxiv2024

APOE3-R136S mutation confers resilience against tau pathology via cGAS-STING-IFN inhibition

The Christchurch mutation (R136S) on the APOE3 (E3S/S) gene is associated with attenuation of tau load and cognitive decline despite the presence of a causal PSEN1 mutation and high levels of amyloid beta pathology in the carrier1. However, the specific molecular mechanisms enabling the E3S/S mutation to mitigate tau-induced neurodegeneration remain unclear. Here, we replaced mouse ApoE with wild-type human E3 or E3S/S on a tauopathy background. The R136S mutation markedly decreased tau load and protected against tau-induced synaptic loss, myelin loss, and reduction in theta and gamma powers. Additionally, the R136S mutation reduced interferon response to tau pathology in both mouse and human microglia, suppressing cGAS-STING activation. Treating tauopathy mice carrying wild-type E3 with a cGAS inhibitor protected against tau-induced synaptic loss and induced similar transcriptomic alterations to those induced by the R136S mutation across brain cell types. Thus, suppression of microglial cGAS-STING-IFN pathway plays a central role in mediating the protective effects of R136S against tauopathy. One-sentence summaryThe R136S mutation on APOE3 enhances resistance to tau-related pathology and toxicity by downregulating the cGAS-STING-IFN signaling pathway.

neuroscience↗

bioRxiv2024

Characterization of a novel zebrafish model of MTMR5-associated CMT4B3

Biallelic loss of expression/function variants in MTMR5 cause the inherited peripheral neuropathy Charcot-Marie-Tooth (CMT) Type 4B3. There is an incomplete understanding of the disease pathomechanism(s) underlying CMT4B3, and despite its severe clinical presentation, currently no disease modifying therapies. A key barrier to the study of CMT4B3 is the lack of pre-clinical models that recapitulate the clinical and pathologic features of the disease. To address this barrier, we generated a zebrafish CRISPR/Cas9 mutant line with a full gene deletion of mtmr5. Resulting homozygous deletion zebrafish are born at normal Mendelian ratios and have preserved motor function. However, starting by 14 day-post-fertilization, mutant zebrafish develop obvious morphometric changes in head size and brain volume. These changes are accompanied at the pathological level by abnormal axon outgrowths and by the presence of dysmyelination, changes reminiscent of the nerve pathology in human CMT4B3. Overall, our mtmr5 zebrafish mirror genetic, clinical, and pathologic features of human CMT4B3. As such, it represents a first pre-clinical model to phenocopy the disease, and an ideal tool for future studies on disease pathomechanism(s) and therapy development. Summary StatementWe created a novel zebrafish mtmr5/sbf1 mutant model of Charcot-Marie-Tooth Type 4B3 that recapitulates key features of the human disorder and provides the first in vivo model for therapy development.

genetics↗

bioRxiv2024

A PTER-dependent pathway of taurine metabolism linked to energy balance

Taurine is a conditionally essential micronutrient and one of the most abundant amino acids in humans1-3. In endogenous taurine metabolism, dedicated enzymes are involved in biosynthesis of taurine from cysteine as well as the downstream derivatization of taurine into secondary taurine metabolites4,5. One such taurine metabolite is N-acetyltaurine6. Levels of N-acetyltaurine are dynamically regulated by diverse physiologic perturbations that alter taurine and/or acetate flux, including endurance exercise7, nutritional taurine supplementation8, and alcohol consumption6,9. While taurine N-acetyltransferase activity has been previously detected in mammalian cells6,7, the molecular identity of this enzyme, and the physiologic relevance of N-acetyltaurine, have remained unknown. Here we show that the orphan body mass index-associated enzyme PTER (phosphotriesterase-related)10 is the principal mammalian taurine N-acetyltransferase/hydrolase. In vitro, recombinant PTER catalyzes bidirectional taurine N-acetylation with free acetate as well as the reverse N-acetyltaurine hydrolysis reaction. Genetic ablation of PTER in mice results in complete loss of tissue taurine N-acetyltransferase/hydrolysis activities and systemic elevation of N-acetyltaurine levels. Upon stimuli that increase taurine levels, PTER-KO mice exhibit lower body weight, reduced adiposity, and improved glucose homeostasis. These phenotypes are recapitulated by administration of N-acetyltaurine to wild-type mice. Lastly, the anorexigenic and anti-obesity effects of N-acetyltaurine require functional GFRAL receptors. Together, these data uncover enzymatic control of a previously enigmatic pathway of secondary taurine metabolism linked to energy balance.

biochemistry↗

bioRxiv2024

Rat primary cortical cell tri-culture to study effects of amyloid-beta on microglia function

IntroductionThe etiology and progression of sporadic Alzheimers Disease (AD) have been studied for decades. One proposed mechanism is that amyloid-beta (A{beta}) proteins induce neuroinflammation, synapse loss, and neuronal cell death. Microglia play an especially important role in A{beta} clearance, and alterations in microglial function due to aging or disease may result in A{beta} accumulation and deleterious effects on neuronal function. However, studying these complex factors in vivo, where numerous confounding processes exist, is challenging, and until recently, in vitro models have not allowed sustained culture of microglia, astrocytes and neurons in the same culture. Here, we employ a tri-culture model of rat primary neurons, astrocytes, and microglia and compare it to co-culture (neurons and astrocytes) and mono-culture enriched for microglia to study microglial function (i.e., motility and A{beta} clearance) and proteomic response to exogenous A{beta}. MethodsWe established cortical co-culture (neurons and astrocytes), tri-culture (neurons, astrocytes, and microglia), and mono-culture (microglia) from perinatal rat pups. On days in vitro (DIV) 7 - 14, the cultures were exposed to fluorescently-labeled A{beta} (FITC-A{beta}) particles for varying durations. Images were analyzed to determine the number of FITC-A{beta} particles after specific lengths of exposure. A group of cells were stained for {beta}III-tubulin, GFAP, and Iba1 for morphological analysis via quantitative fluorescence microscopy. Cytokine profiles from conditioned media were obtained. Live-cell imaging with images acquired every 5 minutes for 4 hours was employed to extract microglia motility parameters (e.g., Euclidean distance, migration speed, directionality ratio). Results and discussionFITC-A{beta} particles were more effectively cleared in the tri-culture compared to the co-culture. This was attributed to microglia engulfing FITC-A{beta} particles, as confirmed via epifluorescence and confocal microscopy. Adding FITC-A{beta} significantly increased the size of microglia, but had no significant effect on neuronal surface coverage or astrocyte size. Analysis of the cytokine profile upon FITC-A{beta} addition revealed a significant increase in proinflammatory cytokines (TNF-, IL-1, IL-1{beta}, IL-6) in tri-culture, but not co-culture. In addition, A{beta} addition altered microglia motility marked by swarming-like motion with decreased Euclidean distance yet unaltered speed. These results highlight the importance of cell-cell communication in microglia function (e.g., motility and A{beta} clearance) and the utility of the tri-culture model to further investigate microglia dysfunction in AD.

neuroscience↗

bioRxiv2024

HER2 Prognostic Significance and Therapeutic Implications in Gastric Cardia Adenocarcinoma: Insights from Multi-Omics Profiling

Therapeutic targets for Gastric Cardia Adenocarcinoma (GCA), particularly for HER2- negative patients, are lacking. Here, we conducted multi-omics profiling on 128 GCA patients using mass spectrometry, whole-exome sequencing, RNA-Seq, and metabolomics. We found HER2 to be a favorable prognostic marker for GCA. Employing molecular counting, we categorized patients into HER2-high, -low, and -negative groups. We uncovered an enrichment of DNA repair features in the HER2-high group, while HER2-low and -negative groups exhibited strong inflammation. We found that tumor mutation burden may not be the distinguishing factor among these three groups. We revealed that the HER2-negative and -low groups have a tumor-suppressive immune microenvironment, and HER2 expression is associated with fatty acid metabolic profiles and inflammation in the blood of patients. Our study revealed anti-inflammatory and immune checkpoint inhibition, targeting PD-L2 and the CD47/SIRPA pair, as therapeutic strategies for HER2-negative GCA patients. These findings highlight promising avenues for personalized treatment for GCA.

cancer biology↗

bioRxiv2024

Testing the mettle of METAL: A comparison of phylogenomic methods using a challenging but well-resolved phylogeny

The evolutionary histories of different genomic regions typically differ from each other and from the underlying species phylogeny. This makes species tree estimation challenging. Here, we examine the performance of phylogenomic methods using a well-resolved phylogeny that nevertheless contains many difficult nodes, the species tree of living birds. We compared trees generated by maximum likelihood (ML) analysis of concatenated data, gene tree summary methods, and SVDquartets. We also conduct the first empirical test of a "new" method called METAL (Metric algorithm for Estimation of Trees based on Aggregation of Loci), which is based on evolutionary distances calculated using concatenated data. We conducted this test using a novel dataset comprising more than 4,000 ultraconserved element (UCE) loci from almost all bird families and two existing UCE and intron datasets sampled from almost all avian orders. We identified "reliable clades" very likely to be present in the true avian species tree and used them to assess method performance. ML analyses of concatenated data recovered almost all reliable clades with less data and greater robustness to missing data than other methods. METAL recovered many reliable clades, but only performed well with the largest datasets. Gene tree summary methods (weighted ASTRAL and weighted ASTRID) performed well; they required less data than METAL but more data than ML concatenation. SVDquartets exhibited the worst performance of the methods tested. In addition to the methodological insights, this study provides a novel estimate of avian phylogeny with almost 99% of the currently recognized avian families. Only one of the 181 reliable clades we examined was consistently resolved differently by ML concatenation versus other methods, suggesting that it may be possible to achieve consensus on the deep phylogeny of extant birds.

evolutionary biology↗

bioRxiv2024

MetaWorm: A Complete Model Bridging Brain, Body and Environment of C. elegans

The behavior of an organism is profoundly influenced by the complex interplay between its brain, body, and environment. Existing data-driven models focusing on either the brain or the body-environment separately. A model that integrates these two components is yet to be developed. Here, we present MetaWorm, an integrative data-driven model of a widely studied organism, C. elegans. This model consists of two sub-models: the brain model and the body & environment model. The brain model was built by multi-compartment models with realistic morphology, connectome, and neural population dynamics based on experimental data. Simultaneously, the body & environment model employed a lifelike body and a 3D physical environment, facilitating easy behavior quantification. Through the closed-loop interaction between two sub-models, MetaWorm faithfully reproduced the realistic zigzag movement towards attractors observed in C. elegans. Notably, MetaWorm is the first model to achieve seamless integration of detailed brain, body, and environment simulations, enabling unprecedented insights into the intricate relationships between neural structures, neural activities, and behaviors. Leveraging this model, we investigated the impact of neural system structure on both neural activities and behaviors. Consequently, MetaWorm can enhance our understanding of how the brain controls the body to interact with its surrounding environment.

neuroscience↗

bioRxiv2024

Discovery of Alkenyl Oxindole as a Novel PROTAC Moiety for Targeted Protein Degradation via CRL4DCAF11 Recruitment

Alkenyl oxindoles have been characterized as autophagosome-tethering compounds (ATTECs), which can target mutant huntingtin protein (mHTT) for lysosomal degradation. In order to expand the application of alkenyl oxindoles for targeted protein degradation, we designed and synthesized a series of hetero-bifunctional compounds by conjugating different alkenyl oxindoles with the BRD4 inhibitor JQ1. Through structure-activity relationship study, we successfully developed JQ1-alkenyl oxindole conjugates that potently degrade BRD4. Unexpectedly, we found that these molecules degrade BRD4 through the ubiquitin-proteasome system, rather than the autophagy-lysosomal pathway. Using pooled CRISPR interference (CRISPRi) screening, we revealed that JQ1-alkenyl oxindole conjugates recruit the E3 ubiquitin ligase complex CRL4DCAF11 for substrate degradation. Furthermore, we validated the most potent hetero-bifunctional molecule HL435 as a promising drug-like lead compound to exert antitumor activity both in vitro and in vivo. Our research provides new employable PROTAC moieties for targeted protein degradation, providing new possibilities for drug discovery.

biochemistry↗

bioRxiv2024

Nonreciprocal synchronization in embryonic oscillator ensembles

Synchronization of coupled oscillators is a universal phenomenon encountered across different scales and contexts e.g., chemical wave patterns, superconductors and the unison applause we witness in concert halls. The existence of common underlying coupling rules define universality classes, revealing a fundamental sameness between seemingly distinct systems. Identifying rules of synchronization in any particular setting is hence of paramount relevance. Here, we address the coupling rules within an embryonic oscillator ensemble linked to vertebrate embryo body axis segmentation. In vertebrates, the periodic segmentation of the body axis involves synchronized signaling oscillations in cells within the presomitic mesoderm (PSM), from which somites, the pre-vertebrae, form. At the molecular level, it is known that intact Notch-signaling and cell-to-cell contact is required for synchronization between PSM cells. However, an understanding of the coupling rules is still lacking. To identify these, we develop a novel experimental assay that enables direct quantification of synchronization dynamics within mixtures of oscillating cell ensembles, for which the initial input frequency and phase distribution are known. Our results reveal a "winner-takes-it-all" synchronization outcome i.e., the emerging collective rhythm matches one of the input rhythms. Using a combination of theory and experimental validation, we develop a new coupling model, the "Rectified Kuramoto" (ReKu) model, characterized by a phase-dependent, non-reciprocal interaction in the coupling of oscillatory cells. Such non-reciprocal synchronization rules reveal fundamental similarities between embryonic oscillators and a class of collective behaviours seen in neurons and fireflies, where higher level computations are performed and linked to non-reciprocal synchronization.

systems biology↗

bioRxiv2024

Transcriptomic and epigenetic responses shed light on soybean resistance to Phytophthora sansomeana

Phytophthora root rot caused by oomycete pathogens in the Phytophthora genus poses a significant threat to soybean productivity. While resistance mechanisms against Phytophthora sojae have been extensively studied in soybean, the molecular basis underlying immune responses to Phytophthora sansomeana remains unclear. We investigated transcriptomic and epigenetic responses of two resistant (Colfax and NE2701) and two susceptible (Williams 82 and Senaki) soybean lines at four time points (2, 4, 8, and 16 hours post inoculation, hpi) after P. sansomeana inoculation. Comparative transcriptomic analyses revealed a greater number of differentially expressed genes (DEGs) upon pathogen inoculation in resistant lines, particularly at 8 and 16 hpi, predominantly associated with ethylene and reactive oxygen species-mediated defense pathways. Moreover, DE transposons were predominantly up-regulated after inoculation and enriched near genes in Colfax. A long non-coding RNA (lncRNA) within the mapped region of the resistance gene exhibited exclusive up-regulation in the resistant lines after inoculation, potentially regulating two flanking LURP-one-related genes. Furthermore, DNA methylation analysis revealed increased CHH methylation levels in lncRNAs after inoculation, with delayed responses in Colfax compared to Williams 82. Overall, our results provide comprehensive insights into soybean responses to P. sansomeana, highlighting potential roles of lncRNAs and epigenetic regulation in plant defense.

plant biology↗

bioRxiv2024

Mitochondrial uncoupler and retinoic acid synergistically induce differentiation and inhibit proliferation in neuroblastoma

Neuroblastoma is a leading cause of death in childhood cancer cases. Unlike adult malignancies, which typically develop from aged cells through accumulated damage and mutagenesis, neuroblastoma originates from neural crest cells with disrupted differentiation. This distinct feature provides novel therapeutic opportunities beyond conventional cytotoxic methods. Previously, we reported that the mitochondrial uncoupler NEN (niclosamide ethanolamine) activated mitochondria respiration to reprogram the epigenome, promoting neuronal differentiation. In the current study, we further combine NEN with retinoic acid (RA) to promote neural differentiation both in vitro and in vivo. The treatment increased the expression of RA signaling and neuron differentiation-related genes, resulting in a global shift in the transcriptome towards a more favorable prognosis. Overall, these results suggest that the combination of a mitochondrial uncoupler and the differentiation agent RA is a promising therapeutic strategy for neuroblastoma.

cancer biology↗

bioRxiv2024

Thiosulfinate tolerance gene clusters are common features of Burkholderia onion pathogens.

Burkholderia gladioli pv. alliicola, B.cepacia, and B. orbicola are common bacterial pathogens of onion. Onions produce organosulfur thiosulfinate defensive compounds after cellular decompartmentalization. Using whole genome sequencing and in silico analysis, we identified putative thiosulfinate tolerance gene (TTG) clusters in multiple onion-associated Burkholderia species similar to those characterized in other Allium-associated bacterial endophytes and pathogens. Sequence analysis revealed the presence of three Burkholderia TTG cluster types with both Type A and Type B being broadly distributed in B. gladioli, B. cepacia, and B. orbicola in both the chromosome and plasmids. Based on isolate natural variation and generation of isogenic strains, we determined the in vitro and in vivo contribution of TTG clusters in B. gladioli, B. cepacia, and B. orbicola. The Burkholderia TTG clusters contributed to enhanced allicin tolerance and improved growth in filtered onion extract by all three species. TTG clusters also made clear contributions to B gladioli foliar necrosis symptoms and bacterial populations. Surprisingly, the TTG cluster did not contribute to bacterial populations in onion bulb scales by these three species. Based on our findings, we hypothesize onion-associated Burkholderia may evade or inhibit the production of thiosulfinates in onion bulb tissues.

microbiology↗

bioRxiv2024

Inhibition of Alpha Interferon-Induced miR-873 Negatively Affects the Hepatitis B Virus Expression

BackgroundAlpha interferon (IFN-)-based therapy can effectively treat chronic hepatitis B virus (HBV) infection, which remains a serious public health problem. This study aims to identify the potential biomarker of IFN treatment and investigate the effects of miR-873 on chronic hepatitis B (CHB). MethodsWe utilized the random forest to screen core differentially expressed miRNAs (DEmiRNAs) based on the miRNA (GSE29911) dataset. DEmiRNAs expressions were determined in clinical samples from CHB patients and normal controls. HBV-transfected hepatoma cell lines were constructed for vitro study. Quantitative real-time reverse transcription PCR (RT-qPCR) was used to determine miRNA mRNA expressions. ELISA assays were used to detect the secretion levels of HBsAg and HBeAg. ResultsBoruta feature selection revealed miR-873 hinting at a predictive marker for IFN response. MiR-873 was significantly up-regulated in the CHB patients, as compared with normal controls (P<0.001). Increased expression of miR-873 was also found in HBV-infected cells (P<0.001). With IFN- treatment, miR-873 was significantly down-regulated in HBV-infected Huh-7 and HepG-NTCP cells (P<0.05). IFN- treatment and miR-873 inhibitor significantly reduced HBsAg and HBeAg level (P<0.05). The inhibitory effect was enhanced by blocking the IFN--induced miR-873 downregulation by inhibitor transfection (P<0.05). In miR-873 mimic-treated cells, the inhibitory effect was greatly supressed by blocking the IFN--induced miR-873 downregulation by mimic transfection (P< 0.01). ConclusionWe provide evidence that inhibition of miR-873 by IFN- enhances the antiviral effects of IFN-. Our study provides a potential strategy to enhance the anti-HBV effect of IFN- by inhibiting miR-873 expression.

molecular biology↗

bioRxiv2023

A Dataset for Deep Learning based Cleavage-stage Blastocyst Prediction with Time-lapse Images

Recent advances in deep learning and artificial intelligence techniques have obtained notable progress in automated embryo image analysis. However, most current research focuses on blastocyst-stage embryo evaluation (more than 5 days after in vitro fertilization), which may reduce the number of transferable embryos and increase the risk of canceled circles. Therefore, this paper aims to investigate the possibility of evaluating blastocyst development at the cleavage stage with deep neural networks (DNNs). To this end, we collect a dataset that consists of time-lapse images of more than 500 embryos (about 194k frames in total). We evaluate several widely used DNNs on the dataset, including those of single-frame architectures and multi-frame architectures. Experimental results show that the accuracy of different DNNs varies from 66.42% to 77.74% and we also provide the possible reasons behind the performance gap. Our dataset and code will be published soon to facilitate related research.

bioinformatics↗

bioRxiv2023

A barley MLA receptor is targeted by a non-ribosomal peptide effector of the necrotrophic spot blotch fungus for disease susceptibility

The evolutionary history of plant interactions with necrotrophic pathogens that feed on dying host cells and their virulence mechanisms remains fragmentary. We have isolated the barley gene Scs6, which is required for the necrotrophic fungus Bipolaris sorokiniana isolate ND90Pr to cause spot blotch disease. Scs6 is located at the disease resistance gene locus Mildew locus a (Mla) and encodes an intracellular nucleotide-binding leucine-rich repeat receptor (NLR). In transgenic barley, Scs6 is sufficient to confer susceptibility to ND90Pr in accessions naturally lacking the receptor, resulting in infection-associated host cell death. Expression of Scs6 in evolutionarily distant Nicotiana benthamiana reconstitutes a cell death response to an uncharacterized non-ribosomal peptide effector produced by ND90Pr-specific non-ribosomal peptide synthetases (NRPSs) encoded at the VHv1 virulence locus. Our data suggest that the heat-resistant effector directly activates the SCS6 receptor. Scs6 is an allelic variant of functionally diversified Mla resistance genes each conferring strain-specific immunity to barley powdery mildew isolates with a matching proteinaceous pathogen effector. Domain swaps between MLA and SCS6 NLRs and expression of the resulting hybrid proteins in N. benthamiana reveal that the SCS6 leucine-rich repeat domain is a specificity determinant for the NRPS-derived effector to activate the receptor. Scs6 evolved after the divergence of barley from wheat and is maintained in several wild barley populations with an incidence of 8%, suggesting a beneficial function for the host. Evolution of the bona fide immune receptor SCS6 targeted by the NRPS-derived effector was key for the emergence of strain-specific spot blotch disease in domesticated barley.

plant biology↗