Biology subjects

Du, B.

Publications and source records attributed to Du, B..

At least 19 recordsLinked to original sources

bioRxiv2026

Multi-scale microenvironment covariance for unsupervised spatial domain identification

Motivation: Many spatial domain identification methods describe the neighbourhood of a cell by mean gene expression. However, the mean cannot separate neighbourhoods that differ only in gene-gene covariance and tissue is organised at several spatial scales. Results: We propose CoSMIM, which represents the niche of each cell by a weighted fusion of gene-gene covariance matrices of its spatial neighbourhood at multiple scales. Principal component analysis and Leiden clustering of the matrix square root of the fused matrix identify spatial domains without model training. On six benchmark datasets from five platforms, CoSMIM attains the best overall rank over eight evaluation metrics among 16 methods. It also ranks first on a Xenium mouse brain dataset, and on all seven datasets its median NMI exceeds that of single-scale COVET. The domain covariance matrices also show gene pairs whose correlation differs between domains.

bioinformatics↗

bioRxiv2026

SHINE: Decoding transcriptional-metabolic microenvironments through higher-order spatial integration

Spatial omics technologies are expanding to co-profile transcriptomics and metabolomics on the same tissue slide, providing complementary views of gene expression and biochemical activity to reveal molecular programs within native tissue microenvironments. However, integrating the transcriptome and metabolome remains technically challenging due to spatial misalignment, resolution disparity, and higher-order cross-modality interactions. Here, we present SHINE, a hypergraph-based computational framework for the joint analysis of spatial gene expression and metabolic networks derived from the co-profiling slide, focusing on representation learning and cross-modality interaction. Across multiple datasets, SHINE consistently outperformed existing methods for domain segmentation and biomarker co-localization, and provided interpretable insights into metabolic-transcriptional microenvironments. Specifically, on Parkinsons disease mouse models, SHINE accurately delineates dopaminergic neuron-depleted regions and reconstructs coherent dopamine-associated axes. In human lung and breast cancers, SHINE resolves tumor-associated spatial regions and identifies spatially organized gene-metabolite programs associated with the tumor microenvironment. SHINE enables scalable spatial multi-omics integration across diverse biological systems.

bioinformatics↗

bioRxiv2025

Chronic kidney disease exacerbates hyperlipidemia and atherosclerosis via miR-148a-3p targeting SIK1/AMPKα1 in liver

BackgroundCardiovascular complications are the leading cause of death in patients with chronic kidney disease (CKD). As a major risk factor for atherosclerotic cardiovascular disease (ASCVD), hyperlipidemia is a common sequela of CKD, which is linked to increased lipid synthesis, impaired lipoprotein clearance, and maladapted reverse cholesterol transport. Because exosomes can transport miRNAs to modulate intercellular and tissue communication, we hypothesized that exosomal miRNAs can act as endocrine-like molecules to modulate the CKD-associated hyperlipidemia and ASCVD. MethodsSmall RNA-seq and qPCR were used to determine the differential plasma level of exosomal miR-148a-3p in ASCVD patients with and without CKD. RNA-seq and in silico analysis were used to establish the regulation of lipid metabolism via miR-148a-3p/salt-inducible kinase 1 (SIK1)/AMP-activated protein kinase alpha 1 subunit (AMPK1) in the liver. Inhibition of miR-148a-3p or overexpression of SIK1/AMPK1 in ApoE-/- mice with 5/6 nephrectomy was used to elucidate the role of the miR-148a-3p/SIK1/AMPK1 axis in CKD-related hyperlipidemia and atherosclerosis. ResultsThe plasma level of exosomal miR-148a-3p was significantly elevated in patients with ASCVD and CKD (ASCVD/CKD) and ApoE-/- mice with 5/6 nephrectomy. Via circulating exosomes, kidney-generated miR-148a-3p was delivered to the liver, where it targeted SIK1/AMPK1 transcripts, thereby upregulating SREBP2/PCSK9 and reciprocally downregulating LDLR. Levels of SIK1 and AMPK1 were decreased in hepatocytes transfected with miR-148a-3p or treated with plasma exosomes from ASCVD/CKD patients, with attendant SREBP2 activation and attenuated LDL-C binding. The decreased LDL-C binding was rectified by SIK1/AMPK1 or LNA-miR-148a-3p overexpression. LNA-miR-148a-3p or AAV8-SIK1/AMPK administration in 5/6 nephrectomy/ApoE-/- mice significantly ameliorated hyperlipidemia and atherosclerosis. ConclusionIn ASCVD/CKD patients and nephrectomy/ApoE-/- mice, kidney-originating miR-148a-3p targeted hepatic SIK1/AMPK1 mRNA. This exosome-mediated endocrine effect upregulated SREBP2/PCSK9 and reciprocally reduced LDLR level, which elevated plasma LDL-C level and exacerbated ASCVD. These findings underscore a kidney-liver-artery axis involved in cardiovascular-kidney-metabolic syndrome.

pathology↗

bioRxiv2025

Stress Granule Formation Drives ZBP1-dependent Necroptosis in Non-obstructive Azoospermia and Aging testes

Male infertility and age-related reproductive decline remain major unmet medical challenges, with limited understanding of the underlying mechanisms. Here, we identify a stress granule-driven necroptosis pathway involving ZBP1 and RIPK3 as a central driver of non-obstructive azoospermia (NOA), a severe form of male infertility marked by loss of spermatogenesis. We show that heat stress or environmental insults activate eIF2 kinases, inducing stress granules that recruit ZBP1 and RIPK3 to form a signaling complex. This leads to RIPK3 activation, MLKL phosphorylation, and necroptotic death of spermatogonia and Sertoli cells. Genetic ablation of Zbp1 or Ripk3 protects mice from heat-induced testicular atrophy, highlighting their essential role in testicular cell death. Notably, this same necroptosis pathway is also activated in aged human testes, suggesting a shared mechanism driving both male infertility and age-related testicular degeneration.

molecular biology↗

bioRxiv2024

Two distinct structural variants involving EDN3 cause hyperpigmentation in chicken

Phenotypic diversity and its genetic basis are central questions in biology, with domesticated animals offering valuable insights due to their rapid evolution the last 10,000 years. In chickens, fibromelanosis (FM) is a striking pigmentation phenotype characterized by hyperpigmentation. A previous study identified a complex structural variant causing upregulated expression of the Endothelin 3 (EDN3) gene. However, the detailed structural arrangement and functional consequences of the variant remained unclear. In this study, we conducted a comprehensive genomic survey of 692 FM chickens representing 55 breeds and uncovered two distinct structural variants causing the FM phenotype: FM*A, the previously reported complex rearrangement involving the EDN3 locus1, and FM*B, a tandem duplication of a 16 kb region upstream of EDN3. We demonstrate that both structural variants (SVs) significantly upregulate EDN3 expression, with FM*B associated with even higher expression than FM*A. A luciferase reporter assays showed that the 16 kb region in FM*B contains powerful enhancers and the copy number expansion of this element is a likely explanation for EDN3 upregulation and hyperpigmentation. Furthermore, our analysis of linkage disequilibrium patterns allowed us to resolve the complex arrangement of duplications and inversion on the FM*A haplotype.

genomics↗

bioRxiv2024

Date palm acclimates to aridity by diverting organic osmolytes for root osmotic adjustment in parallel with leaf membrane remodeling and ROS scavenging

Highlight statementOsmotic strength of date palm roots increases with soil desiccation, for which the accumulation of organic osmolytes, such as sugars, is essential in complement to energetically cheap mineral osmotics. Date palm (Phoenix dactylifera L.) is an important crop in arid regions that is well-adapted to desert ecosystems. To understand the remarkable ability to grow and yield in water-limited environments, experiments were conducted in a simulated desert environment with water-withholding for up to four weeks. In response to drought, root, rather than leaf, osmotic strength increased, with sugars contributing more to the osmolyte increase than minerals. Consistently, carbon and amino acid metabolism was acclimated toward biosynthesis at both the transcriptional and translational levels. In leaves, a remodeling of membrane systems was observed, suggesting changes in thylakoid lipid composition, which together with the restructuring of the photosynthetic apparatus, indicated an acclimation preventing oxidative damage. Thus, xerophilic date palm avoids oxidative damage under drought by combined prevention and rapid detoxification of oxygen radicals. Although minerals were expected to serve as cheap key osmotics, date palm also relies on organic osmolytes for osmotic adjustment of the roots during desiccation. The diversion of these resources away from growth is consistent with date palms strategy of generally slow growth in harsh environments and clearly indicates a trade-off between growth and stress-related physiological responses.

plant biology↗

bioRxiv2023

Inferring Neuron-level Brain Circuit Connection via Graph Neural Network Amidst Small Established Connections

MotivationReconstructing neuron-level brain circuit network is a universally recognized formidable task. A significant impediment involves discerning the intricate interconnections among multitudinous neurons in a complex brain network. However, the majority of current methodologies only rely on learning local visual synapse features while neglecting the incorporation of comprehensive global topological connectivity information. In this paper, we consider the perspective of network connectivity and introduce graph neural networks to learn the topological features of brain networks. As a result, we propose Neuronal Circuit Prediction Network (NCPNet), a simple and effective model to jointly learn node structural representation and neighborhood representation, constructing neuronal connection pair feature for inferring neuron-level connections in a brain circuit network. ResultsWe use a small number of connections randomly selected from a single brain circuit network as training data, expecting NCPNet to extrapolate known connections to unseen instances. We evaluated our model on Drosophila connectome and C. elegans worm connectome. The numerical results demonstrate that our model achieves a prediction accuracy of 91.88% for neuronal connections in the Drosophila connectome when utilizing only 5% of known connections. Similarly, under the condition of 5% known connections in C. elegans, our model achieves an accuracy of 93.79%. Additional qualitative analysis conducted on the learned representation vectors of Kenyon cells indicates that NCPNet successfully acquires meaningful features that enable the discrimination of neuronal sub-types. Our project is available at https://github.com/mxz12119/NCPNet.

neuroscience↗

bioRxiv2023

The transcription factor OsbZIP48 governs rice responses to zinc deficiency

Zinc deficiency is the most prevalent micronutrient disorder in rice and leads to delayed development and decreased yield. Nevertheless, despite its primary importance, how rice responds to zinc deficiency remains poorly understood. Herein, we present genetic evidence that OsbZIP48 is essential for regulating rice responses to zinc deficiency. Using the reverse genetics approach, genetic inactivation of OsbZIP48 in rice seedlings caused a hyper sensitivity to zinc deficiency, associated with a significant decrease in the root-to-shoot translocation of zinc. Consistently, OsbZIP48 was constitutively expressed in roots, slightly induced by zinc deficiency in shoots, and localized into nuclei induced by Zn deficiency. Comparative transcriptome analysis of the wild-type plants and osbzip48 mutant grown under zinc deficiency enabled the identification of OsbZIP48 target genes, including key zinc transporter genes (OsZIP4 and OsZIP8). We demonstrated that OsbZIP48 controlled the expressions of these genes by directly binding to their promoters, specifically to the zinc deficiency response element (ZDRE) motif. Collectively, we showed that the OsbZIP48 gene encodes for a transcription factor in rice, and demonstrates its critical role in the response to zinc deficiency in this crop. This knowledge is crucial for the design of rice plants that are resilient to the globally prevalent zinc limitation through zinc bio-fortification programs.

plant biology↗

bioRxiv2023

Resolving the developmental mechanisms of coagulation abnormalities characteristic of SARS-CoV2 based on single-cell transcriptome analysis

The COVID-19 outbreak caused by the SARS-CoV-2 virus has developed into a global health emergency. In addition to causing respiratory symptoms following SARS-CoV-2 infection, COVID-19-associated coagulopathy (CAC) is the main cause of death in patients with severe COVID-19. In this study, we performed single-cell sequencing analysis of the right ventricular free wall tissue from healthy donors, patients who died in the hypercoagulable phase of CAC, and patients in the fibrinolytic phase of CAC. Among these, we collected 61,187 cells, which were enriched in 24 immune cell subsets and 13 cardiac-resident cell subsets. We found that in response to SARS-CoV-2 infection, CD9highCCR2highmonocyte-derived mo promoted hyperactivation of the immune system and initiated the extrinsic coagulation pathway by activating CXCR-GNB/G-PI3K-AKT. This sequence of events is the main process contributing the development of coagulation disorders subsequent to SARS-CoV-2 infection. In the characteristic coagulation disorder caused by SARS-CoV-2, excessive immune activation is accompanied by an increase in cellular iron content, which in turn promotes oxidative stress and intensifies intercellular competition. This induces cells to alter their metabolic environment, resulting in an increase in sugar uptake, such as that via the glycosaminoglycan synthesis pathway, in CAC coagulation disorders. In addition, high levels of reactive oxygen species generated in response elevated iron levels promote the activation of unsaturated fatty acid metabolic pathways in endothelial cell subgroups, including vascular endothelial cells. This in turn promotes the excessive production of the toxic peroxidation by-product malondialdehyde, which exacerbates both the damage caused to endothelial cells and coagulation disorders.

microbiology↗

bioRxiv2022

Identification of S1PR4 as an immune modulator for favorable prognosis in HNSCC through unbiased machine learning

As the largest family of membrane proteins, G protein-coupled receptors (GPCRs) are the most prominent family of pharmacological targets. However, only a few GPCRs have been well-defined in terms of their physiological and pathological functions. Thus, an efficient way to identify key GPCRs involved in tumour formation is urgently needed. In this study, patients with head and neck squamous cell carcinoma (HNSCC) were classified into two different subtypes based on the characteristics of GPCRs using an unbiased machine learning method. Notably, these two subtypes showed significant differences in prognosis, gene expression, and immune microenvironment, especially in the infiltration of CD8+ T cells. Based on these differences, we screened three potential key regulators (S1PR4, S1PR5, and GPR87) from all GPCRs and constructed a prognostic nomogram for patients with HNSCC. We identified S1PR4 as the key GPCR in determining the two subtypes for positive correlation with the proportion and cytotoxicity of CD8+ T cells in HNSCC and was mainly expressed in a subset of CX3CR1+CD8+ T cells. We also demonstrated that S1PR4 is an immune modulator for the favourable prognosis of HNSCC patients. We found that S1PR4 was highly expressed in CD8+ T cells from the tumours of HNSCC patients, which was significantly associated with better prognosis, and S1PR4 expression was accompanied by higher T cell cytotoxic marker expression (IFNG and GZMB). Notably, S1PR4 co-localised with CX3CR1, which has been identified as the most cytotoxic marker of CD8+ T cells. Furthermore, S1PR4 upregulation could significantly increase T cell function in CAR-T cell therapy, indicating its great potential in cancer immunotherapy. Therefore, these results identified S1PR4 as a key indicator of cytotoxicity and the proportion of tumour-infiltrating CD8+ T cells and confirmed the prognostic value of S1PR4 in HNSCC. Our findings contribute to the knowledge of S1PR4 in anti-tumour immunity, providing a potential GPCR-targeted therapeutic option for future HNSCC treatment.

cancer biology↗

bioRxiv2022

A Novel Gene REPTOR2 Activates the Autophagic Degradation of Wing Disc in pea aphid

Wing dimorphism is an evolutionarily adaptive trait to maximize insect fitness under various environments, by which the population could be balanced between migration and reproduction. Most studies concern the regulatory mechanisms underlying the stimulation of wing morph in aphids, but relatively little research addresses the molecular basis of wing loss. Here, we found that the wing disc of wingless-destined pea aphids degenerated 30 h post birth by autophagic rather than apoptotic degeneration, whereas winged-destined aphids developed normally. Activation of autophagy in 1st instar nymphs reduced the proportion of winged aphids, and suppression of autophagy increased the proportion. The REPTOR2 gene associated with TOR signaling pathway was identified by RNA-seq as a differentially expressed gene between the two morphs, with higher expression in the thorax of wingless-destined aphids. Further genetic analysis indicated that REPTOR2 could be a novel gene derived from a gene duplication event exclusively in pea aphid on autosome A1 but translocated to the sex chromosome. Knockdown of REPTOR2 reduced autophagy in the wing disc and increased the proportion of winged aphids. In agreement with REPTORs canonical negative regulatory role of TOR on autophagy, winged-destined aphids had higher TOR expression in the wing disc. Suppression of TOR activated autophagy of the wing disc and decreased the proportion of winged aphids, and vice versa. These results revealed that the TOR signaling pathway controlled degradation of the wing disc in pea aphids, and that REPTOR2 could modulate this autophagic degradation.

developmental biology↗

bioRxiv2022

Preclinical evaluation of RQ3013, a broad-spectrum mRNA vaccine against SARS-CoV-2 variants

The global emergence of SARS-CoV-2 variants has led to increasing breakthrough infections in vaccinated populations, calling for an urgent need to develop more effective and broad-spectrum vaccines to combat COVID-19. Here we report the preclinical development of RQ3013, an mRNA vaccine candidate intended to bring broad protection against SARS-CoV-2 variants of concern (VOCs). RQ3013, which contains pseudouridine-modified mRNAs formulated in lipid nanoparticles, encodes the spike(S) protein harboring a combination of mutations responsible for immune evasion of VOCs. Here we characterized the expressed S immunogen and evaluated the immunogenicity, efficacy, and safety of RQ3013 in various animal models. RQ3013 elicited robust immune responses in mice, hamsters, and nonhuman primates (NHP). It can induce high titers of antibodies with broad cross-neutralizing ability against the Wild-type, B.1.1.7, B.1.351, B.1.617.2, and the omicron B.1.1.529 variants. In mice and NHP, two doses of RQ3013 protected the upper and lower respiratory tract against infection by SARS-CoV-2 and its variants. We also proved the safety of RQ3013 in NHP models. Our results provided key support for the evaluation of RQ3013 in clinical trials.

immunology↗

bioRxiv2022

A scalp geometry parameter-space for optimization and implementation of conventional TMS coil placement

Transcranial magnetic stimulation efficacy is largely dependent upon coil position and orientation. A good method for describing coil placement is required for both computational optimization (planning) and actual placement (implementation). In coordinate dependent parameter-spaces (CDPs), three-dimensional coordinates are used to represent coil position and three orthogonal unit vectors are used to represent coil orientation. A CDP can precisely describe arbitrary coil placement; therefore it offers great advantage in computational optimization which checks through all possible placements. However, a neuronavigation system is usually required to accurately implement the optimized CDP parameters on a participants head. Routine clinical practice, on the other hand, often uses the International 10-20 system to describe coil placement. Although the 10-20 system can only perform modeling and placement at limited scalp landmarks, it allows the synthesis of different individuals targeting effects to find group-optimal parameters; it also allows manual placement, which is important for commonly-seen use cases without individual MRI scans and navigation devices. This study proposes a new scalp geometry based parameter-space (SGP), integrating the advantages of CDP and 10-20 methods. Our SGP 1) can quantitatively specify all possible conventional coil positions and orientations on an individuals scalp, which is important for electrical modeling and optimization, 2) maintains inter-individual correspondence, which is important for synthesizing TMS effects from different individuals and studies. 3) enables fast and simple manual implementation. Demonstration experiments were conducted to illustrate the application of an SGP-based framework for both individual and group-based optimization. A measurement experiment was performed to evaluate speed, precision and reliability of SGP-based manual implementation; results show it surpasses previous manual placement methods.

neuroscience↗

bioRxiv2021

Non-canonical Function of a Hif-1α Splice Variant Contributes to the Sustained Flight of Locusts

The hypoxia inducible factor (Hif) pathway is functionally conserved across metazoans in modulating cellular adaptations to hypoxia. However, the functions of this pathway under aerobic physiological conditions are rarely investigated. Here, we show that Hif-12, a locust Hif-1 isoform, does not induce canonical hypoxic responses but functions as a specific regulator of locust flight, which is a completely aerobic physiological process. Two Hif-1 splice variants were identified in locusts, a ubiquitously expressed Hif-11 and a muscle-predominantly expressed Hif-12. Hif-11 that induces typical hypoxic responses upon hypoxia exposure, remains inactive during flight. By contrast, the expression of Hif-12, which lacks C-terminal transactivation domain, is less sensitive to oxygen-tension but induced extensively by flying. Hif-12 sustains flight endurance by promoting glucose oxidation while simultaneously maintaining redox homeostasis by upregulating the production of a reactive oxygen species (ROS) quencher, DJ-1. Overall, this study reveals a novel Hif-mediated mechanism underlying prolonged aerobic physiological activity.

zoology↗

bioRxiv2021

Multi-omics analysis for potential inflammation-related genes involved in tumor immune evasion via extended application of epigenetic data

BackgroundAccumulating evidence suggests that inflammation-related genes may play key roles in tumor immune evasion. Programmed cell death ligand 1 (PD-L1) is an important immune checkpoint involved in mediating antitumor immunity. We performed multi-omics analysis to explore key inflammation-related genes affecting the transcriptional regulation of PD-L1 expression. MethodsThe open chromatin region of the PD-L1 promoter was mapped using the assay for transposase-accessible chromatin using sequencing (ATAC-seq) profiles. Correlation analysis of epigenetic data (ATAC-seq) and transcriptome data (RNA-seq) were performed to identify inflammation-related transcription factors whose expression levels were correlated with the chromatin accessibility of the PD-L1 promoter. Chromatin immunoprecipitation sequencing (ChIP-seq) profiles were used to confirm the physical binding of the TF STAT2 and the predicted binding regions. We also confirmed the results of the bioinformatics analysis with cell experiments. ResultsWe identified chr9:5449463-5449962 and chr9:5450250-5450749 as reproducible open chromatin regions in the PD-L1 promoter. Moreover, we observed a correlation between STAT2 expression and the accessibility of the aforementioned regions. Furthermore, we confirmed its physical binding through ChIP-seq profiles and demonstrated the regulation of PD-L1 by STAT2 overexpression in vitro. Multiple databases were also used for the validation of the results. ConclusionOur study identified STAT2 as a direct upstream TF regulating PD-L1 expression. The interaction of STAT2 and PD-L1 might be associated with tumor immune evasion in cancers, suggesting the potential value for tumor treatment.

immunology↗

bioRxiv2021

Development of Large-Scale Brain Network Dynamics in Children

Functional brain networks require dynamic reconfiguration to support flexible cognitive function. However, the developmental principles shaping brain network dynamics remain poorly understood. Here, we report the longitudinal development of large-scale brain network dynamics during childhood and adolescence, and its connection with gene expression profiles. Using a multilayer network model, we show the temporally varying modular architecture of child brain networks, with higher network switching primarily in the association cortex and lower switching in the primary regions. This topographical profile exhibits progressive maturation, which manifests as reduced modular dynamics, particularly in the transmodal (e.g., default-mode and frontoparietal) and sensorimotor regions. These developmental refinements mediate age-related enhancements of global network segregation and are linked with the expression profiles of genes associated with the enrichment of ion transport and nucleobase-containing compound transport. These results highlight a progressive stabilization of brain dynamics, which expand our understanding of the neural mechanisms that underlie cognitive development.

neuroscience↗

bioRxiv2021

Structural basis of substrate recognition and translocation by human ABCA4

Human ATP-binding cassette (ABC) subfamily A (ABCA) transporters mediate the transport of various lipid compounds across the membrane. Mutations in human ABCA transporters have been described to cause severe hereditary disorders associated with impaired lipid transport. However, little is known about the mechanistic details of substrate recognition and translocation by ABCA transporters. Here, we present three cryo-EM structures of human ABCA4, a retinal-specific ABCA transporter, in distinct functional states at resolutions of 3.3-3.4 [A]. In the nucleotide-free state, the two transmembrane domains (TMDs) exhibited a lateral-opening conformation, allowing the lateral entry of substrate from the lipid bilayer. N-retinylidene-phosphatidylethanolamine (NRPE), the physiological lipid substrate of ABCA4, is sandwiched between the two TMDs in the luminal leaflet and is further stabilized by an extended loop from extracellular domain 1. In the ATP-bound state, the two TMDs displayed an unprecedented closed conformation, which precludes the substrate binding. Our study provides a molecular basis to understand the mechanism of ABCA4-mediated NRPE recognition and translocation, and suggests a common lateral access and extrusion mechanism for ABCA-mediated lipid transport.

biochemistry↗

bioRxiv2020

Changes in the plasmodesma structure and permeability at the bundle sheath and mesophyll interface during the maize C4 leaf development

Plasmodesmata are intercellular channels that facilitate molecular diffusion between neighboring plant cells. The development and functions of plasmodesmata are controlled by multiple intra- and intercellular signaling pathways. Plasmodesmata are critical for dual-cell C4 photosynthesis in maize because plasmodesmata at the mesophyll and bundle sheath interface mediate exchange of CO2-carrying organic acids. We examined developmental profiles of plasmodesmata and chloroplasts in the maize leaf from young cells in the base to mature cell in the tip using microscopy approaches. Young mesophyll and bundle sheath cells in the leaf base had proplastids, and their plasmodesmata were simple, devoid of cytoplasmic sleeves. In maturing cells where Kranz anatomy and dimorphic chloroplasts were evident, we observed extensive remodeling of plasmodesmata that included acquisition of an electron-dense ring on the mesophyll side and cytoplasmic sleeves on the bundle sheath side. Interestingly, the changes in plasmodesmata involved a drop in symplastic dye mobility and suberin accumulation in the cell wall, implying a more stringent mesophyll-bundle sheath transport. We compared kinetics of the plasmodesmata and the cell wall modification in wildtype leaves with leaves from ppdk and dct2 mutants with defective C4 pathways. Plasmodesmata development, symplastic transport inhibition, and cell wall suberization were accelerated in the mutant lines, probably due to the aberrant C4 cycle. Transcriptomic analyses of the mutants confirmed the expedited changes in the cell wall. Our results suggest that a regulatory machinery at the mesophyll-bundle sheath boundary suppresses erroneous flux of C4 metabolites in the maize leaf. Significance StatementPlasmodesmata in the maize Kranz anatomy mediate the exchange of organic acids between mesophyll and bundle sheath. Since solute diffusion through plasmodesmata is governed by solute concentration gradients, a balanced distribution of C4 metabolites is critical for concentration of CO2 in the bundle sheath. Plasmodesmata bridging the mesophyll and bundle sheath cytoplasm have a cylindrical cavity, which can facilitate molecular movements, and a valve-like attachment. Construction of the sophisticated plasmodesmata was linked to C4 photosynthesis, and plasmodesmata assembly finished more rapidly in maize mutants with defective C4 pathways than in wild-type plants. These results suggest that the specialized plasmodesmata contribute to controlled transport of C4 metabolites.

plant biology↗