Biology subjects

Ren, Z.

Publications and source records attributed to Ren, Z..

At least 91 records · Page 5Linked to original sources

bioRxiv2022

Inhibitory effects of GT0918 on acute lung injury and the molecular mechanisms of anti-inflammatory response

Coronavirus disease 2019 (COVID-19) has caused the public health crisis in the whole world. Anti-androgens block severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry and protect against severe clinical COVID-19 outcomes. GT0918, a novel androgen receptor antagonist, accelerated viral clearance and increased recovery rate in outpatients by blocking SARS-CoV-2 infection though down-regulating ACE2 and TMPRSS2 expression. Further clinical study showed that GT0918 reduced mortality rate and shortened hospital stay in hospitalized COVID-19 patients. GT0918 also exhibits protective efficacy in severe COVID-19 patient in critical care. However, the mechanism of GT0918 treatment for severe COVID-19 disease is unknown. Here, we found GT0918 decreased the expression and secretion of proinflammatory cytokines through NF-{kappa}B signaling pathway. The acute lung injury induced by LPS or Poly(I:C) was also attenuated in GT0918-treated mice, compared with vehicle control group. Moreover, GT0918 elevated the NRF2 protein level but not mRNA transcription activity. GT0918 induced proinflammatory cytokines downregulation was partially dependent on NRF2. In conclusion, our data demonstrate that GT0918 reduced cytokine release and suppressed inflammatory responses through inhibiting NF-{kappa}B signaling and activating NRF2. GT0918 is not only effective for treatment of mild to moderate COVID-19 patients, but also a potential therapeutic drug for severe COVID-19 patients by reducing the risk of cytokine storm and acute respiratory distress syndrome.

cell biology↗

bioRxiv2022

Assessment of urinary exosome NHE3 as a biomarker of acute kidney injury

The diagnosis of acute kidney injury (AKI) traditionally depends on the serum creatinine (SCr) and urine output, which lack sufficient sensitivity and specificity. Urinary exosome as a biomarker has unique advantages. To assessed whether urinary exosome Na+/H+ exchanger isoform 3 (NHE3) protein as a nonivasive diagnostic biomarker of AKI, we constructed 4 AKI rat models: cisplatin (7.5mg/kg) injection intraperitoneally (IP), furosemide (20mg/kg, IP) with low NaCl (0.03%) diet, low NaCl (0.03%) diet with candesartan (1mg/kg, IP) and bilaterally ischemia and reperfusion(I/R) injury for 40 minutes. Besides, we assessed 6 sepsis associated AKI patients and 6 healthy volunteers. Urinary exosomes were extracted by ultra-centrifugation and NHE3 protein abundance was tested by immunoblotting in all AKI rats and human subjects. The isolated cup-shape particles with an average diameter of 70nm and enrichment in CD63 were identified as exosomes. NHE3 abundance was 6 times higher in exosome than in original urine. In cisplatin induced AKI rats, urinary exosome NHE3 was increased at day 2, 1 day earlier than the increases of serum creatinine creatinine (SCr) and blood urea nitrogen (BUN). In additional rats, urinary exosome NHE3 decreased along with the decline of SCr after EPO pretreatment. In volume depletion AKI induced by furosemide injection with low NaCl diet, urinary exosome NHE3 expression was higher than control. In low NaCl diet with candesartan related AKI, urinary exosome NHE3 was elevated at day 5, 2 days earlier than SCr. In I/R injury AKI, urinary exosome NHE3 was also raised compared with control. In humans, the urinary exosome NHE3 level was also elevated in sepsis associated AKI patients in comparison with the healthy volunteers. Then urinary exosome NHE3 protein may be used as a noninvasive diagnostic biomarker of AKI. Impact StatementThe high non-recognition acute kidney injury (AKI) is due to lacking of alarming symptoms or specific early biomarkers. Urinary exosome as a biomarker has unique advantages. In our study, we detected urinary exosome NHE3 protein abundance in 4 different cause of AKI rat model. Urinary exosome NHE3 was increased in all 4 AKI, and even elevated earlier than SCr in some cases. Another novel point was we established a new AKI model of low NaCl diet with candesartan injection, which was common in patients with hypertension or proteinuria clinically. The detailed methods and mechanisms of this new AKI model were presented in another article being submitted. Third, we are not limited to animals, but also selected sepsis associated AKI patients to study. The conclusion that urinary exosome NHE3 may be used as a diagnosis biomarker of AKI has important clinical application value.

molecular biology↗

bioRxiv2022

Transcriptomic analysis reveals hub genes and pathways in response to acetic acid stress in Kluyveromyces marxianus during high-temperature ethanol fermentation

The thermotolerant yeast Kluyveromyces marxianus has great potential for high-temperature ethanol fermentation, but it produces excess acetic acid during high-temperature fermentation, which inhibits ethanol production. The mechanisms of K. marxianuss responses to acetic acid have not been fully understood. In this study, the transcriptomic changes of K. marxianus DMKU3-1042 resulted from acetic acid stress during high-temperature ethanol fermentation were investigated based on high-throughput RNA sequencing. We identified 611 differentially expressed genes (DEGs) under acetic acid stress (fold change > 2 or < 0.5, P-adjust <0.05), with 166 up-regulated and 445 down-regulated. GO terms and pathways enriched in these DEGs were identified. Protein-protein interaction (PPI) networks were constructed based on the interactions between proteins coded by the DEGs, and hub genes and key modules in the PPI networks were identified. The results in this study indicated that during high-temperature fermentation, acetic acid stress promoted protein catabolism but repressed protein synthesis, which affected the growth and metabolism of K. marxianus and led to the decrease of ethanol production. The findings in this study provide a better understanding of the response mechanism of K. marxianus to acetic acid stress, and provide a basis for subsequent increase of ethanol production by K. marxianus.

microbiology↗

bioRxiv2022

Multi-task learning for single-cell multi-modality biology

Current biotechnologies can simultaneously measure multi-modality high-dimensional information from the same cell and tissue samples. To analyze the multi-modality data, common tasks such as joint data analysis and cross-modal prediction have been developed. However, current analytical methods are generally designed to process multi-modality data for one specific task without considering the underlying connections between tasks. Here, we present UnitedNet, a multi-task deep neural network that integrates the tasks of joint group identification and cross-modal prediction to analyze multi-modality data. We have found that multi-task learning for joint group identification and cross-modal prediction significantly improves the performance of each task. When applied to various single-cell multi-modality datasets, UnitedNet shows superior performance in each task, achieving better unsupervised and supervised joint group identification and cross-modal prediction performances compared with state-of-the-art methods. Furthermore, by considering the spatial information of cells as one modality, UnitedNet substantially improves the accuracy of tissue region identification and enables spatially resolved cross-modal prediction.

genomics↗

bioRxiv2022

Roles of RodZ and Class A PBP1b in the Assembly and Regulation of the Peripheral Peptidoglycan Elongasome in Ovoid-Shaped Cells of Streptococcus pneumoniae D39

RodZ of rod-shaped bacteria functions to link MreB filaments to the Rod peptidoglycan (PG) synthase complex that moves circumferentially perpendicular to the long cell axis, creating hoop-like sidewall PG. Ovoid-shaped bacteria, such as Streptococcus pneumoniae (pneumococcus; Spn) that lack MreB, use a different modality for peripheral PG elongation that emanates from the midcell of dividing cells. Yet, S. pneumoniae encodes a RodZ homolog similar to RodZ in rod-shaped bacteria. We show here that the helix-turn-helix and transmembrane domains of RodZ(Spn) are essential for growth at 37{degrees}C. {Delta}rodZ mutations are suppressed by {Delta}pbp1a, mpgA(Y488D), and {Delta}khpA mutations that suppress {Delta}mreC, but not {Delta}cozE. Consistent with a role in PG elongation, RodZ(Spn) co-localizes with MreC and aPBP1a throughout the cell cycle and forms complexes and interacts with PG elongasome proteins and regulators. Depletion of RodZ(Spn) results in aberrantly shaped, non-growing cells and mislocalization of elongasome proteins MreC, PBP2b, and RodA. Moreover, Tn-seq reveals that RodZ(Spn), but not MreCD(Spn), displays a specific synthetic-viable genetic relationship with aPBP1b, whose function is unknown. We conclude that RodZ(Spn) acts as a scaffolding protein required for elongasome assembly and function and that aPBP1b, like aPBP1a, plays a role in elongasome regulation and possibly peripheral PG synthesis. Graphical Summary O_FIG O_LINKSMALLFIG WIDTH=192 HEIGHT=200 SRC="FIGDIR/small/494439v1_ufig1.gif" ALT="Figure 1"> View larger version (47K): org.highwire.dtl.DTLVardef@f1cfb9org.highwire.dtl.DTLVardef@17cac68org.highwire.dtl.DTLVardef@1af20borg.highwire.dtl.DTLVardef@108d83c_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2022

Proximal Exploration for Model-guided Protein Sequence Design

Designing protein sequences with a particular biological function is a long-lasting challenge for protein engineering. Recent advances in machine-learning-guided approaches focus on building a surrogate sequence-function model to reduce the burden of expensive in-lab experiments. In this paper, we study the exploration mechanism of model-guided sequence design. We leverage a natural property of protein fitness landscape that a concise set of mutations upon the wild-type sequence are usually sufficient to enhance the desired function. By utilizing this property, we propose Proximal Exploration (PEX) algorithm that prioritizes the evolutionary search for high-fitness mutants with low mutation counts. In addition, we develop a specialized model architecture, called Mutation Factorization Network (MuFacNet), to predict low-order mutational effects, which further improves the sample efficiency of model-guided evolution. In experiments, we extensively evaluate our method on a suite of in-silico protein sequence design tasks and demonstrate substantial improvement over baseline algorithms.

bioinformatics↗

bioRxiv2022

De-heterogeneity of the eukaryotic viral reference database (EVRD) improves the accuracy and efficiency of viromic analysis

Widespread in public databases, the notorious contamination in virus reference databases often leads to confusing even wrong conclusions in applications like viral disease diagnosis and viromic analysis, highlighting the need of a high-quality database. Here, we report the comprehensive scrutiny and the purification of the largest viral sequence collections of GenBank and UniProt by detection and characterization of heterogeneous sequences (HGSs). A total of 766 nucleotide- and 276 amino acid-HGSs were determined with length up to 6,605 bp, which were widely distributed in 39 families, with many involving highly public health-related viruses, such as hepatitis C virus, Crimea-Congo hemorrhagic fever virus and filovirus. Majority of these HGSs are sequences of a wide range of hosts including humans, with the rest resulting from vectors, misclassification and laboratory components. However, these HGSs cannot be simply considered as exotic contaminants, since part of which are resultants of natural occurrence or artificial engineering of the viruses. Nevertheless, they significantly disturb the genomic analysis, and hence were deleted from the database. A further augmentation was implemented with addition of the risk and vaccine sequences, which finally results in a high-quality eukaryotic virus reference database (EVRD). EVRD showed higher accuracy and less time-consuming without coverage compromise by reducing false positives than other integrated databases in viromic analysis. EVRD is freely accessible with favorable application in viral disease diagnosis, taxonomic clustering, viromic analysis and novel virus detection.

microbiology↗

bioRxiv2022

ECD of PepT1 interacts with TM1 to facilitate substrate transport

Mammalian peptide transporters, PepT1 and PepT2, mediate uptake of a wide variety of di- and tri-peptides and are essential for the absorption of dietary peptides in the digestive tract and the recovery of peptides in renal filtrate. PepT also mediates absorption of many drugs and prodrugs to enhance their bioavailability. PepT has 12 transmembrane (TM) helices that fold into two domains, the N-terminal domain (NTD, TM1-6) and C-terminal domain (CTD, TM7-12), and a large extracellular domain (ECD) of [~]200 amino acids between TM9 and TM10. It is known that peptide transport involves large motions of the N- and C-domains, but the role of ECD remains unclear. Here we report the structure of PepT1 from Equus caballus (horse) determined by cryo-electron microscopy. The structure shows that ECD interacts with TM1 and bridges the N- and C-domains. Deletion of the ECD or mutations to the TM1-ECD interface both impair the transport activity. These results demonstrate a role of ECD in structure and function of PepT1 and enhance our understanding of the mechanism of transport in PepT1.

biochemistry↗

bioRxiv2022

High-dimension to high-dimension screening for detecting genome-wide epigenetic regulators of gene expression

MotivationThe advancement of high-throughput technology characterizes a wide range of epigenetic modifications across the genome involved in disease pathogenesis via regulating gene expression. The high-dimensionality of both epigenetic and gene expression data make it challenging to identify the important epigenetic regulators of genes. Conducting univariate test for each epigenetic-gene pair is subject to serious multiple comparison burden, and direct application of regularization methods to select epigenetic-gene pairs is computationally infeasible. Applying fast screening to reduce dimension first before regularization is more efficient and stable than applying regularization methods alone. ResultsWe propose a novel screening method based on robust partial correlation to detect epigenetic regulators of gene expression over the whole genome, a problem that includes both high-dimensional predictors and high-dimensional responses. Compared to existing screening methods, our method is conceptually innovative that it reduces the dimension of both predictor and response, and screens at both node (epigenetic features or genes) and edge (epigenetic-gene pairs) levels. We develop data-driven procedures to determine the conditional sets and the optimal screening threshold, and implement a fast iterative algorithm. Simulations and two applications to long non-coding RNA and DNA methylation regulation in Kidney cancer and Glioblastoma Multiforme illustrate the validity and advantage of our method. AvailabilityThe R package, related source codes and real data sets used in this paper are provided at https://github.com/kehongjie/rPCor.

bioinformatics↗

bioRxiv2022

Hypercapnia limits β-catenin mediated alveolar type 2 cell progenitor function by altering Wnt production from adjacent fibroblasts

Persistent symptoms and radiographic abnormalities suggestive of failed lung repair are among the most common symptoms in patients with COVID-19 after hospital discharge. In mechanically ventilated patients with ARDS secondary to SARS-CoV-2 pneumonia, low tidal volumes to reduce ventilator-induced lung injury necessarily elevate blood CO2 levels, often leading to hypercapnia. The role of hypercapnia on lung repair after injury is not completely understood. Here, we show that hypercapnia limits {beta}-catenin signaling in alveolar type 2 (AT2) cells, leading to reduced proliferative capacity. Hypercapnia alters expression of major Wnts in PDGFRa+-fibroblasts from those maintaining AT2 progenitor activity and towards those that antagonize {beta}-catenin signaling and limit progenitor function. Activation of {beta}-catenin signaling in AT2 cells, rescues the inhibition AT2 proliferation induced by hypercapnia. Inhibition of AT2 proliferation in hypercapnic patients may contribute to impaired lung repair after injury, preventing sealing of the epithelial barrier, increasing lung flooding, ventilator dependency and mortality.

cell biology↗

bioRxiv2022

Stem embolism vulnerability curve depends on methods used: is there a fifth mechanism of cavitation?

A long-established ecological paradigm predicts a functional relationship determining vulnerability to cavitation: vulnerability increases with vessel hydraulic efficiency and vessel diameter. Even within a species, big vessels cavitate before small ones. Some centrifuge methods for measuring vulnerability are prone to artifacts due to nano-particles seeding early embolism, as the particles are drawn into vessels during measurements. Both the Sperry and Cochard rotors are prone to early cavitation due to nano-particles drawn into long and wide vessels in Robinia pseudoacacia and Quercus acutissima, whereas extraction centrifuge methods produce vulnerability curves more resistant to cavitation. Sufficient nano-particles pass through the stems to seed early embolism in all rotor designs. For several years, people have thought that early embolism is induced by nano-particles present in laboratory water. One new hypothesis is that the origin of nano-particles is from cut-open living cells but a much bigger study including many species is required to confirm this idea. This paper confirms the hypothesis in comparisons between short-vesselled Acer, and long-vesselled Robinia, and Quercus. Our new results and a review of old results justifies bigger study. Hypothetical nano-particles might explain why different methods for measuring vulnerability curves cause different T50 = tensions causing 50% loss of hydraulic conductivity. Hence the hypothesis for future research should be that the open-vessel artifact is consistent with long vessels surrounded by cut open living cells. One sentence SummaryNano-particles induced early cavitation in species with vessel lengths about [1/4] the stem length used in all centrifuge rotors, and the origin of nano-particles might be from living cells nearby vessels

physiology↗

bioRxiv2021

Insight into the mechanism of H+-coupled nucleobase transport

Members of the nucleobase/ascorbic acid transporter (NAT) gene family are found in all kingdoms of life. In mammals, the concentrative uptake of ascorbic acid (vitamin C) by members of the NAT family is driven by the Na+ gradient, while the uptake of nucleobases in bacteria is powered by the H+ gradient. Here we report the structure and function PurTCp, a NAT family member from Colwellia psychrerythraea. The structure of PurTCp was determined to 2.80 [A] resolution by X-ray crystallography. PurTCp forms a homodimer and each protomer has 14 transmembrane segments folded into a substrate-binding domain (core domain) and an interface domain (gate domain) A purine base is present in the structure and defines the location of the substrate binding site. Functional studies reveal that PurTCp transports purines but not pyrimidines, and that purine binding and transport is dependent on the pH. Mutation of a conserved aspartate residue close to the substrate binding site reveals the critical role of this residue in H+-dependent transport of purines. Comparison of the PurTCp structure with transporters of the same structural fold suggests that rigid-body motions of the substrate-binding domain are central for substrate translocation across the membrane.

biochemistry↗

bioRxiv2021

CAMO: A molecular congruence analysis framework for evaluating model organisms

CAMO provides a rigorous and user-friendly solution for quantification and mechanistic exploration of omics congruence in model organisms and humans. It performs threshold-free differential analysis, quantitative concordance/discordance scoring, pathway-centric investigation, and topological subnetwork detection. Instead of dichotomous claims of "poorly" or "greatly" mimicking humans, CAMO facilitates discovery and visualization of specific molecular mechanisms that are best or least mimicked, providing foundations for hypothesis generation and subsequent translational investigations.

genomics↗

bioRxiv2021

Directional proton conductance in bacteriorhodopsin is driven by concentration gradient, not affinity gradient

Many microorganisms can harvest energy from sun light to establish electrochemical potential across cell membrane by pumping protons outward. Light driven proton pumping against a transmembrane gradient entails exquisite electronic and conformational reconfigurations at fs to ms time scales. However, transient molecular events along the photocycle of bacteriorhodopsin are difficult to comprehend from noisy and inconsistent electron density maps obtained from multiple experiments. A major challenge arises from the coexisting intermediate populations as a heterogenous conformational mixture continuously evolves over 13 decades in time. This study reports a meta-analysis of the recent time-resolved datasets collected by several consortia. By resolving structural heterogeneity, this in-depth analysis substantially improves the quality of the electron density maps, and provides a clear visualization of the isolated intermediates from I to M. The earliest photoproducts revealed by the deconvoluted maps suggest that a proton transfer uphill against 15 pH units is accomplished by the same physics governing the tablecloth trick. While the Schiff base is displaced at the beginning of the photoisomerization within ~30 fs, the proton stays due to its inertia. This affinity-independent early deprotonation builds up a steep proton concentration gradient that subsequently drives the directional proton conductance toward the extracellular medium. This mechanism fundamentally deviates from the widely adopted notion on multiple steps of chemical equilibrium driven by light-induced changes of proton affinity. The method of a numerical resolution of concurrent events from mixed observations is also generally applicable. Significance StatementMicroorganisms can exploit solar energy to offset their cellular acidity from the environment by pumping protons outward under light illumination. The ability to transport ions across the cell membrane in response to light makes this family of small transmembrane proteins a highly desirable toolkit in development of new biotechnologies. It is important to understand how these ion pumps operate at the molecular level. This study finds that the outward proton conductance through bacteriorhodopsin, the most studied model system in the class, is driven by a steep concentration gradient of protons established in the light induced process rather than by an affinity gradient previously sought for decades. Summary of RevisionThis is the companion manuscript of another paper already published in PNAS Nexus (Ren, Photoinduced isomerization sampling of retinal in bacteriorhodopsin, PNAS Nexus, 1(3), 2022, 10.1093/pnasnexus/pgac103). The original version of this manuscript was submitted to PNAS Nexus on February 18, 2022. The manuscript was reviewed by three reviewers and the Decision Notification was received on April 5, 2022. I appealed the decision to reject the manuscript on May 28, 2022, and the appeal was accepted. A revised version of the manuscript was submitted on July 25, 2022, with an extensive response to the peer review. The editor sent the revised version and the response to peer review back to the three reviewers. Reviewer 3 declined to review the revised manuscript. The editor extended the invitation to several other scientists to review the revised manuscript. All of them declined to review. The second Decision Notification based on the opinions of Reviewers 1 and 2 was received on September 14, 2022. The revised manuscript, the supplementary materials, and all review documents are listed below in the Table of contents. Second revision is underway.

biochemistry↗

bioRxiv2021

Photoinduced isomerization sampling of retinal in bacteriorhodopsin

Photoisomerization of retinoids inside a confined protein pocket represents a critical chemical event in many important biological processes from animal vision, non-visual light effects, to bacterial light sensing and harvesting. Light driven proton pumping in bacteriorhodopsin entails exquisite electronic and conformational reconfigurations during its photocycle. However, it has been a major challenge to delineate transient molecular events preceding and following the photoisomerization of the retinal from noisy electron density maps when varying populations of intermediates coexist and evolve as a function of time. Here I report several distinct early photoproducts deconvoluted from the recently observed mixtures in time-resolved serial crystallography. This deconvolution substantially improves the quality of the electron density maps hence demonstrates that the all-trans retinal undergoes extensive isomerization sampling before it proceeds to the productive 13-cis configuration. Upon light absorption, the chromophore attempts to perform trans-to-cis isomerization at every double bond together with the stalled anti-to-syn rotations at multiple single bonds along its polyene chain. Such isomerization sampling pushes all seven transmembrane helices to bend outward, resulting in a transient expansion of the retinal binding pocket, and later, a contraction due to recoiling. These ultrafast responses observed at the atomic resolution support that the productive photoreaction in bacteriorhodopsin is initiated by light-induced charge separation in the prosthetic chromophore yet governed by stereoselectivity of its protein pocket. The method of a numerical resolution of concurrent events from mixed observations is also generally applicable. Significance StatementPhotoisomerization of retinal is a critical rearrangement reaction in many important biological processes from animal vision, non-visual light effects, to bacterial light sensing and harvesting. It has been a major challenge to visualize rapid molecular events preceding and following photoisomerization so that many protein functions depending on such reaction remain vaguely understood. Here I report a direct observation of the stereoselectivity of bacteriorhodopsin hence delineate the structural mechanism of isomerization. Upon a light-induced charge separation, the retinal in a flat conformation attempts to perform double bond isomerization and single bond rotation everywhere along its polyene chain before it proceeds to the specific, productive configuration. This observation improves our understanding on how a non-specific attraction force could drive a specific isomerization.

biochemistry↗

bioRxiv2021

Interfered Chromosome Pairing Promotes Meiosis Instability of Autotetraploid Arabidopsis by High Temperatures

Alterations of environmental temperature affect multiple meiosis processes in flowering plants. Polyploid plants derived from whole genome duplication (WGD) have enhanced genetic plasticity and tolerance to environmental stress, but meanwhile face a challenge for organization and segregation of doubled chromosome sets. In this study, we investigated the impact of increased environmental temperature on male meiosis in autotetraploid Arabidopsis thaliana. Under low to mildly-increased temperatures (5-28{degrees}C), irregular chromosome segregation universally takes place in synthesized autotetraploid Columbia-0 (Col-0). Similar meiosis lesions occur in autotetraploid rice (Oryza sativa L.) and allotetraploid canola (Brassica napus cv. Westar), but not in evolutionary-derived hexaploid wheat (Triticum aestivum). As temperature increases to extremely high, chromosome separation and tetrad formation are severely disordered due to univalent formation caused by suppressed crossing-over. We found a strong correlation between tetravalent formation and successful chromosome pairing, both of which are negatively correlated with temperature elevation, suggesting that increased temperature interferes with crossing-over prominently by impacting homolog pairing. Besides, we showed that loading irregularities of axis proteins ASY1 and ASY4 co-localize on the chromosomes of syn1 mutant, and the heat-stressed diploid and autotetraploid Col-0, revealing that heat stress affects lateral region of synaptonemal complex (SC) by impacting stability of axis. Moreover, we showed that chromosome axis and SC in autotetraploid Col-0 are more sensitive to increased temperature than that of diploid Arabidopsis. Taken together, our study provide evidence suggesting that WGD without evolutionary and/or natural adaption negatively affects stability and thermal tolerance of meiotic recombination in Arabidopsis thaliana.

plant biology↗

bioRxiv2021

Abundant and rare bacterial taxa structuring differently in sediment and water in thermokarst lakes in the Yellow River Source area, Qinghai-Tibet Plateau

Thermokarst lakes are forming from permafrost thaw and severely affected by accelerating climate change. Sediment and water in these lakes are distinct habitats but closely connected. However, our understanding of the differences and linkages between sediment and water in thermokarst lakes remain largely unknow, especially from the perspective of community assembly mechanisms. Here, we examined bacterial communities in sediment and water in thermokarst lakes in the Yellow River Source area, Qinghai-Tibet Plateau. Bacterial taxa were divided to abundant and rare according to their relative abundance, and the Sorensen dissimilarity ({beta}sor) was partitioned into turnover ({beta}turn) and nestedness ({beta}nest). The whole bacterial communities as well as the abundant and rare subcommunities differed substantially between sediment and water, in terms of taxonomical composition, -diversity, and {beta}-diversity. Sediment had significantly lower -diversity indexes but higher {beta}-diversity than water. Abundant taxa had significantly higher relative abundances but lower -diversity and {beta}-diversity than rare taxa. Moreover, bacterial communities are predominantly governed by strong turnover processes ({beta}turn/{beta}sor ratio of 0.925). Abundant subcommunities were significantly lower in {beta}turn/{beta}sor ratio compared to rare subcommunities. Bacterial communities in sediment had a significantly higher {beta}turn/{beta}sor ratio than in water. The results suggest that the bacterial communities of thermokarst lakes, especially rare subcommunities or particularly in sediment, might be strongly structured by environmental filtering and geographical isolation, leading to compositional distinct. This integral study increased our current knowledge of thermokarst lakes, enhancing our understanding of the community assembly rules and ecosystem structures and processes of these rapid changing and vulnerable ecosystems.

microbiology↗

bioRxiv2021

The Magnaporthe oryzae MAP kinase Pmk1 regulates polycomb repressive complex 2 to reprogram genes expression for biotrophic growth

Biotrophic and hemibiotrophic fungi have evolved the ability to colonize living plant cells, but how they establish biotrophic growth by remodeling gene expression is poorly understood. By using in planta invasive hyphae (IH) of Magnaporthe oryzae to perform an integrated Chromatin immunoprecipitation sequencing (ChIPseq) and RNA-seq analysis, combining with biological and cellular analyses, we found Polycomb repressive complex 2 (PRC2)-mediated epigenetic repression plays a key role in regulating biotrophic growth. ChIPseq for biotrophic IH samples identified 1701 PRC2 target genes. RNA-seq analysis showed that expression of 462 PRC2 target genes were up-regulated in the {Delta}suz12 mutant, while 82 were down-regulated, indicating a major role of PRC2 in gene repression of IH. During biotrophic growth, PRC2 repressed fungal cell wall synthesis genes and extracellular enzyme genes required for penetration, and secondary metabolites biosynthesis genes required for necrotrophic growth. A great number of effector-encoding genes were repressed by PRC2, which were highly expressed during penetration stage, suggesting PRC2 coordinates biotrophic growth by regulating effector suppression for immune evasion. This regulation was finely coordinated by Pmk1, through regulating phosphorylation, nuclear localization and protein abundance of Suz12. Our results indicate that the Pmk1-PRC2 regulatory module is required for gene remodeling to facilitate biotrophic growth in M. oryzae. IMPORTANCEBiotrophic and hemibiotrophic fungi establish a biotrophic stage for infection in host cells. For example, M. oryzae forms appressoria to penetrate host cell and establish a biotrophic growth stage for infection. How gene expression patterns are elaborately controlled for fungal biotrophic growth is largely unknown. In this study, we found that, the PRC2-mediated H3K27me3 repressed fungal penetration-required cell wall synthesis genes and extracellular enzyme genes, and necrotrophic growth-required secondary metabolites biosynthesis genes for biotrophic growth. Interestingly, a great number of effector-encoding genes were also repressed by PRC2 at biotrophic stage, which were highly expressed at penetration stage, suggesting PRC2 coordinates biotrophic growth by regulating effector suppression for immune evasion. The PRC2-mediated epigenetic repression is therefore required for the gene expression remodeling during fungal infection. This regulation was finely coordinated by Pmk1, through regulating nuclear localization and protein abundance of the PRC2 component Suz12.

microbiology↗