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Liu, L.

Publications and source records attributed to Liu, L..

At least 343 records · Page 19Linked to original sources

SciMind: A Multimodal Mixture-of-Experts Model for Advancing Pharmaceutical Sciences

Large language models (LLMs) have made substantial strides, but their use in reliably tackling issues within specialized domains, particularly in interdisciplinary areas like pharmaceutical sciences, is hindered by data heterogeneity, knowledge complexity, unique objectives, and a spectrum of constraint conditions. In this area, diverse modalities such as nucleic acids, proteins, molecular structures, and natural language are often involved. We designed a specialized token set and introduced a new Mixture-of-Experts (MoEs) pre-training and fine-tuning strategy to unify these modalities in one model. With this strategy, weve created a multi-modal mixture-of-experts foundational model for pharmaceutical sciences, named SciMind. This model has undergone extensive pre-training on publicly accessible datasets including nucleic acid sequences, protein sequences, molecular structure strings, and biomedical texts, and delivers good performance on biomedical text comprehension, promoter prediction, protein function prediction, molecular description, and molecular generation.

bioinformatics↗

Spatiotemporal transcriptomic profiling and modeling of mouse brain at single-cell resolution reveals cell proximity effects of aging and rejuvenation

Old age is associated with a decline in cognitive function and an increase in neurodegenerative disease risk1. Brain aging is complex and accompanied by many cellular changes2-20. However, the influence that aged cells have on neighboring cells and how this contributes to tissue decline is unknown. More generally, the tools to systematically address this question in aging tissues have not yet been developed. Here, we generate spatiotemporal data at single-cell resolution for the mouse brain across lifespan, and we develop the first machine learning models based on spatial transcriptomics ( spatial aging clocks) to reveal cell proximity effects during brain aging and rejuvenation. We collect a single-cell spatial transcriptomics brain atlas of 4.2 million cells from 20 distinct ages and across two rejuvenating interventions--exercise and partial reprogramming. We identify spatial and cell type-specific transcriptomic fingerprints of aging, rejuvenation, and disease, including for rare cell types. Using spatial aging clocks and deep learning models, we find that T cells, which infiltrate the brain with age, have a striking pro-aging proximity effect on neighboring cells. Surprisingly, neural stem cells have a strong pro-rejuvenating effect on neighboring cells. By developing computational tools to identify mediators of these proximity effects, we find that pro-aging T cells trigger a local inflammatory response likely via interferon-{gamma} whereas pro-rejuvenating neural stem cells impact the metabolism of neighboring cells possibly via growth factors (e.g. vascular endothelial growth factor) and extracellular vesicles, and we experimentally validate some of these predictions. These results suggest that rare cells can have a drastic influence on their neighbors and could be targeted to counter tissue aging. We anticipate that these spatial aging clocks will not only allow scalable assessment of the efficacy of interventions for aging and disease but also represent a new tool for studying cell-cell interactions in many spatial contexts.

neuroscience↗

Equip Fusobacterium nucleatum genetic tool kits with compatible shuttle vectors and engineered intermediatory E. coli strains for enhanced transformation efficiency

Fusobacterium nucleatum, an oral microbe, is implicated in various human diseases, including oral-related diseases and tumors. However, efficient transformation was only achieved in limited strains of this bacterium. The challenges in conducting molecular level investigations of most strains due to their genetic intractability have hindered the biological studies of F. nucleatum. The restriction-modification (RM) systems is one of the known obstacles for efficient DNA transformation. Here, we used single molecule real time sequencing to elucidate the RM recognition sites and the corresponding methyltransferases (MTases) in two F. nucleatum strains. Based on the identified MTases, we engineered intermediatory E. coli host strains to bypass the RM systems, and showed that the plasmids harbored by these intermediatory strains can be efficiently electro-transformed, reaching 5000 transformants per microgram plasmids, paving the way for the development of efficient genetic modification tools. Furthermore, we successfully demonstrated that the conjugation-based DNA delivery to F. nucleatum can bypass the requirement of MTase methylations. By exploring the native plasmids from F. nucleatum, we identified new backbones for construction of shuttle vectors and established a dual-plasmid system for the first time, offering new avenues for genetic manipulation in this bacterium. Additionally, we evaluate promoters with variable strengths with a luciferase-based reporter system in F. nucleatum, providing valuable insights for future gene editing studies in bacterium and contributing to our understanding of its pathogenesis. All the tools developed in this study was shared via the WeKwikgene (https://wekwikgene.wllsb.edu.cn/). Impact StatementFusobacterium nucleatum, a key opportunistic pathogen implicated in periodontal diseases, rheumatoid arthritis, and tumors, presents significant challenges due to its limited transformation efficiency and lack of gene-editing tools. In this study, we present an advancement -a streamlined and robust pipeline that enhances transformation efficiency by approximately 103-fold in F. nucleatum, reaching 5000 CFU per microgram plasmids. This represents a significant breakthrough, marking the first report to achieve such a remarkable improvement in transformation efficiency in this pathogen. This improvement paves the way for the genome-wide level mutagenesis study in this bacterium.

microbiology↗

Preclinical validation and kinetic modelling of the SV2A PET ligand UCB-J in mice

Synaptic vesicle protein 2A (SV2A) is ubiquitously expressed in presynaptic terminals where it functions as a neurotransmission regulator protein. Synaptopathy has been reported during healthy ageing and in a variety of neurodegenerative diseases. Positron emission tomography (PET) imaging of SV2A can be used to evaluate synaptic density. The PET ligand [11C]UCB-J has high binding affinity and selectivity for SV2A but has a short physical half-life due to the 11C isotope. Here we report the characterization and validation of its 18F-labeled equivalent, [18F]UCB-J, in terms of specificity, reproducibility and stability in C57BL/6J mice. Plasma analysis revealed at least one polar radiometabolite. Kinetic modelling was performed using a population-based metabolite corrected image-derived input function (IDIF). [18F]UCB-J showed relatively fast kinetics and a reliable measure of the IDIF-based volume of distribution (VT(IDIF)). [18F]UCB-J specificity for SV2A was confirmed through a levetiracetam blocking assay (50 to 200 mg/kg). Reproducibility of the VT(IDIF) was determined through test-retest analysis, revealing significant correlation (r2=0.773, p<0.0001). Time-stability analyses indicate a scan duration of 60 min to be sufficient to obtain a reliable VT(IDIF). In conclusion, [18F]UCB-J is a selective SV2A ligand with optimal kinetics in mice. Further investigation is warranted for (pre)clinical applicability of [18F]UCB-J in synaptopathies.

neuroscience↗

Aspartic proteases are abundant and active in acidified wound fluid

Wound healing necessitates a balance between synthesis and breakdown of extracellular matrix components, which is tightly regulated by proteases and their inhibitors. Studies have shown that treatment of poorly healing wounds with acid results in improved healing. In this study, we systematically evaluated changes in proteolytic activity of murine wound fluid upon acidification. A library of 228 synthetic peptides served as reporters of protease activity at pH 7.4, pH 5.0 and pH 3.5. The peptide digestion patterns differed at each pH, revealing that proteases active at pH 7.4 are inactivated at pH 3.5. Notably, aspartic acid proteases emerged as the dominant active enzymes at pH 3.5 and their activity was inhibited by pepstatin. Using a fluorogenic substrate, we quantified aspartic protease activity across varying pH levels and demonstrated optimal activity between pH 3.0 and 3.8. This activity was detectable as early as one day post-injury and persisted over the following ten days. Importantly, human wound fluid exhibited the same activity profile, validating the mouse model as a relevant system for studying acid-mediated wound healing processes.

biochemistry↗

The pathogenicity of PSEN2 variants is tied to Aβ production and homology to PSEN1

INTRODUCTIONThough recognized as a potential cause of Autosomal Dominant Alzheimers Disease, the pathogenicity of many PSEN2 variants remains uncertain. We compared A{beta} production across all missense PSEN2 variants in the Alzforum database and, when possible, to corresponding PSEN1 variants. METHODSWe expressed 74 PSEN2 variants, 21 of which had homologous PSEN1 variants with the same amino acid substitution, in HEK293 cells lacking PSN1/2. A{beta} production was compared to age at symptom onset (AAO) and between homologous PSEN1/2 variants. RESULTSA{beta}42/40 and A{beta}37/42 ratios were associated with AAO across PSEN2 variants, strongly driven by PSEN2 variants with PSEN1 homologs. PSEN2 AAO was 18.3 years later compared to PSEN1 homologs. A{beta} ratios from PSEN1/2 homologs were highly correlated, suggesting a similar mechanism of {gamma}-secretase dysfunction. DISCUSSIONThe existence of a PSEN1 homolog and patterns of A{beta} production are important considerations in assessing the pathogenicity of previously-reported and new PSEN2 variants.

neuroscience↗

Restoring hippocampal glucose metabolism rescues cognition across Alzheimer's disease pathologies

Impaired cerebral glucose metabolism is a pathologic feature of Alzheimer Disease (AD), and recent proteomic studies highlight a disruption of glial carbohydrate metabolism with disease progression. Here, we report that inhibition of indoleamine-2,3-dioxygenase 1 (IDO1), which metabolizes tryptophan to kynurenine (KYN) in the first step of the kynurenine pathway, rescues hippocampal memory function and plasticity in preclinical models of amyloid and tau pathology by restoring astrocytic metabolic support of neurons. Activation of IDO1 in astrocytes by amyloid-beta42 and tau oligomers, two major pathological effectors in AD, increases KYN and suppresses glycolysis in an AhR-dependent manner. Conversely, pharmacological IDO1 inhibition restores glycolysis and lactate production. In amyloid-producing APPSwe-PS1{Delta}E9 and 5XFAD mice and in tau-producing P301S mice, IDO1 inhibition restores spatial memory and improves hippocampal glucose metabolism by metabolomic and MALDI-MS analyses. IDO1 blockade also rescues hippocampal long-term potentiation (LTP) in a monocarboxylate transporter (MCT)-dependent manner, suggesting that IDO1 activity disrupts astrocytic metabolic support of neurons. Indeed, in vitro mass-labeling of human astrocytes demonstrates that IDO1 regulates astrocyte generation of lactate that is then taken up by human neurons. In co-cultures of astrocytes and neurons derived from AD subjects, deficient astrocyte lactate transfer to neurons was corrected by IDO1 inhibition, resulting in improved neuronal glucose metabolism. Thus, IDO1 activity disrupts astrocytic metabolic support of neurons across both amyloid and tau pathologies and in a model of AD iPSC-derived neurons. These findings also suggest that IDO1 inhibitors developed for adjunctive therapy in cancer could be repurposed for treatment of amyloid- and tau-mediated neurodegenerative diseases.

neuroscience↗

Discovery of a Heparan-Sulfate Binding Domain in Monkeypox Virus H3 Protein as a New Anti-poxviral Drug Target

Viral adhesion to host cells is a critical step in infection for many viruses, including monkeypox virus (MPXV). In MPXV, the H3 protein mediates viral adhesion through its interaction with heparan sulfate (HS), yet the structural details of this interaction have remained elusive. Using AI-based structural prediction tools and molecular dynamics (MD) simulations, we identified a novel, positively charged -helical domain in H3 that is essential for HS binding. This conserved domain, found across orthopoxviruses, was experimentally validated and shown to be critical for viral adhesion, making it an ideal target for antiviral drug development. Targeting this domain, we designed a protein inhibitor, which disrupted the H3-HS interaction, inhibited viral infection in vitro and viral replication in vivo, offering a promising antiviral candidate. Our findings reveal a novel therapeutic target of MPXV, demonstrating the potential of combination of AI-driven methods and MD simulations to accelerate antiviral drug discovery.

biophysics↗

Genomic evolution reshapes cell type diversification in the amniote brain

Over 320 million years of evolution, amniotes have developed complex brains and cognition through largely unexplored genetic and gene expression mechanisms. We created a comprehensive single-cell atlas of over 1.3 million cells from the telencephalon and cerebellum of turtles, zebra finches, pigeons, mice, and macaques, employing single-cell resolution spatial transcriptomics to validate gene expression patterns across species. Our study revealed significant species-specific variations in cell types, highlighting their conservation and diversification in evolution. We found pronounced differences in telencephalon excitatory neurons (EX) and cerebellar cell types between birds and mammals. Birds predominantly express SLC17A6 in EX, whereas mammals expressed SLC17A7 in neocortex and SLC17A6 elsewhere, possibly due to loss of SLC17A7 function loss in birds. Additionally, we identified a novel bird-specific Purkinje cell subtype (SVIL+), implicating the LSD11/KDM1A pathway in learning and circadian rhythms, and related numerous positively selected genes in birds, suggesting an evolutionary optimization of cerebellar functions for ecological and behavioral adaptation. Our findings elucidate the complex interplay between genetic evolution and environmental adaptation, underscoring the role of genetic diversification in the development of specialized cell types across amniotes.

evolutionary biology↗

Modification of regulatory tyrosines biases human Hsp90α for interaction with cochaperones and clients

The highly conserved Hsp90 chaperones control stability and activity of many essential signaling and regulatory proteins including many protein kinases, E3 ligases and transcription factors. Thereby, Hsp90s couple cellular homeostasis of the proteome to cell fate decisions. High-throughput mass spectrometry revealed 178 and 169 posttranslational modifications (PTMs) for human cytosolic Hsp90 and Hsp90{beta}, but for only a few of the modifications the physiological consequences are investigated in some detail. In this study, we explored the suitability of the yeast model system for the identification of key regulatory residues in human Hsp90. Replacement of three tyrosine residues known to be phosphorylated by phosphomimetic glutamate and by non-phosphorylatable phenylalanine individually and in combination influenced yeast growth and the maturation of 7 different Hsp90 clients in distinct ways. Furthermore, wild-type and mutant Hsp90 differed in their ability to stabilize known clients when expressed in HepG2 HSP90AA1-/- cells. The purified mutant proteins differed in their interaction with the cochaperones Aha1, Cdc37, Hop and p23 and in their support of the maturation of glucocorticoid receptor ligand binding domain in vitro. In vivo and in vitro data correspond well to each other confirming that the yeast system is suitable for the identification of key regulatory sites in human Hsp90s. Our findings indicate that even closely related clients are affected differently by the amino acid replacements in the investigated positions, suggesting that PTMs could bias Hsp90s client specificity.

molecular biology↗

RSG-YOLO: Detection of rice seed germination rate based on enhanced YOLOv8 and multi-scale attention feature fusion

The lack of obvious difference between germinated seeds and non-germinated seeds will cause the low accuracy of detecting rice seed germination rate, remains a challenging issue in the field. In view of this, a new model named Rice Seed Germination-YOLO (RSG-YOLO) is proposed in this paper. This model initially incorporates CSPDenseNet to streamline computational processes while preserving accuracy. Furthermore, the BRA, a dynamic and sparse attention mechanism is integrated to highlight critical features while minimizing redundancy. The third advancement is the employment of a structured feature fusion network, based on GFPN, aiming to reconfigure the original Neck component of YOLOv8, thus enabling efficient feature fusion across varying levels. An additional detection head is introduced, improving detection performance through the integration of variable anchor box scales and the optimization of regression losses. This paper also explores the influence of various attention mechanisms, feature fusion techniques, and detection head architectures on the precision of rice seed germination rate detection. Experimental results indicate that RSG-YOLO achieves a mAP50 of 0.981, marking a 4% enhancement over the mAP50 of YOLOv8 and setting a new benchmark on the RiceSeedGermination dataset for the detection of rice seed germination rate.

plant biology↗

Unveiling the mechanisms of black phosphorus nanosheets-induced viable but non-culturable state in Bacillus tropicus

The release of black phosphorus (BP) nanosheets has raised concerns regarding potential ecological risks. Previous studies have confirmed their toxicity to bacteria, but discrepancies were observed between results obtained from the growth curve and colony forming unit (CFU) methods, indicating the possibility of bacterial cells entering a viable but non-culturable (VBNC) state induced by BP nanosheets. To accurately assess the risks, it is crucial to understand the underlying mechanisms. In this study, we investigated the effect of BP nanosheets on Bacillus tropicus, a gram-positive bacterium, using transcriptome sequencing and biological assays. Our findings revealed that BP nanosheets caused minimal cell death but predominately induced the VBNC state in most cells. At the transcriptional level, we observed significant down-regulation of pathways associated with cellular metabolism and respiratory chain in response to BP nanosheet treatment. Bacterial cells in the VBNC state exhibited depressed respiration to maintain basal cellular activity. Additionally, the reduced cellular respiration and metabolic activity were associated with a decrease in antibiotic susceptibility of the bacteria. These results provide new insights into the antibacterial mechanisms of BP nanosheets and emphasize the necessity of employing appropriate approaches, beyond the traditional CFU method, to assess the bacterial toxicity of nanomaterials. Environmental implicationBacteria play a crucial role as indicators in ecological risk assessment. Although numerous studies have highlighted the exceptional antibacterial properties of black phosphorus (BP) nanosheets, the unique viable but non-culturable (VBNC) state of bacteria is often overlooked when evaluating the ecological risks of nanomaterial, including BP nanosheets. In our study, we found that BP nanosheets can induce Bacillus tropicus into a VBNC state by suppressing cellular metabolism- and respiratory chain-related pathways, shedding light on their ecological risk assessment implications. This finding underscores the importance of utilizing appropriate approaches in evaluating the bacterial toxicity of nanomaterials.

pharmacology and toxicology↗

Tripartite organization of brain state dynamics underlying spoken narrative comprehension

Speech comprehension involves the dynamic interplay of multiple cognitive processes, from basic sound perception, to linguistic encoding, and finally to complex semantic-conceptual interpretations. How the brain handles the diverse streams of information processing remains poorly understood. Applying Hidden Markov Modeling to fMRI data obtained during spoken narrative comprehension, we reveal that the whole brain networks predominantly oscillate within a tripartite latent state space. These states are respectively characterized by high activities in the sensory-motor (State #1), bilateral temporal (State #2), and DMN (State #3) regions, with State #2 acting as a transitional hub. The three states are selectively modulated by the acoustic, word-level semantic and clause-level semantic properties of the narrative. Moreover, the alignment with the best performer in brain state expression can predict participants narrative comprehension scores. These results are reproducible with different brain network atlas and generalizable to two datasets consisting of young and older adults. Our study suggests that the brain underlies narrative comprehension by switching through a tripartite state space, with each state probably dedicated to a specific component of language faculty, and effective narrative comprehension relies on engaging those states in a timely manner.

neuroscience↗

Preeclampsia-specific immune cell network in placenta revealed by Cytometry by time of flight and single-cell RNA-seq

Preeclampsia (PE), a major cause of maternal and perinatal mortality with highly heterogeneous causes and symptoms, is usually complicated by gestational diabetes mellitus (GDM). However, a comprehensive understanding of the immune microenvironment in the placenta of PE and the differences between PE and GDM is still lacking. In this study, Cytometry by time of flight (CyTOF) indicated that the frequencies of memory-like Th17 cells (CD45RA-CCR7+IL-17A+CD4+), memory-like CD8+ T cells (CD38+CXCR3-CCR7+Helios-CD127-CD8+) and pro-inflam Macs (CD206-CD163-CD38midCD107alowCD86midHLA-DRmidCD14+) were increased, while the frequencies of anti-inflam Macs (CD206+CD163-CD86midCD33+HLA-DR+CD14+) and granulocyte myeloid-derived suppressor cells (gMDSCs, CD11b+CD15hiHLA-DRlow) were decreased in the placenta of PE compared with that of NP, but not in that of GDM or GDM&PE. The pro-inflam Macs were positively correlated with memory-like Th17 cells and memory-like CD8+ T cells but negatively correlated with gMDSCs. Single-cell RNA sequencing revealed that transferring the F4/80+CD206- pro-inflam Macs with a Folr2+Ccl7+Ccl8+C1qa+C1qb+C1qc+ phenotype from the uterus of PE mice to normal pregnant mice induced the production of memory-like IL-17a+Rora+Il1r1+TNF+Cxcr6+S100a4+CD44+ Th17 cells via IGF1-IGF1R, which contributed to the development and recurrence of PE. Pro-inflam Macs also induced the production of memory-like CD8+ T cells but inhibited the production of Ly6g+S100a8+S100a9+Retnlg+Wfdc21+ gMDSCs at the maternal-fetal interface, leading to PE-like symptoms in mice. In conclusion, this study revealed the PE-specific immune cell network, which was regulated by pro-inflam Macs, providing new ideas about the pathogenesis of PE.

immunology↗

CLCC1 Governs Bilayer Equilibration at the Endoplasmic Reticulum to Maintain Cellular and Systemic Lipid Homeostasis

The intricate orchestration of lipid production, storage, and mobilization is vital for cellular and systemic homeostasis1,2. Dysfunctional plasma lipid control represents the major risk factor for cardio-metabolic diseases, the leading cause of human mortality3,4. Within the cellular landscape, the endoplasmic reticulum (ER) is the central hub of lipid synthesis and secretion, particularly in metabolically active hepatocytes in the liver or enterocytes in the gut5,6. Initially assembled in the ER lumen, lipid-ferrying lipoproteins necessitate the cross-membrane transfer of both neutral and phospho-lipids onto the lumenal apolipoprotein B (APOB), in a poorly-defined process7-10. Here we show that trans-bilayer equilibration of phospholipids, regulated by the ER protein CLCC1, determines lipid partition across the ER membrane and consequently systemic lipid homeostasis. CLCC1 partners with the phospholipid scramblase TMEM41B11,12 to recognize imbalanced bilayers and promote lipid scrambling, thereby licensing lipoprotein biogenesis and the subsequent bulk lipid transport. Strikingly, loss of CLCC1 or TMEM41B leads to the emergence of giant lumenal lipid droplets enclosed by extensively imbalanced ER bilayers, and consequently drastically accelerated pathogenesis of metabolic-dysfunction-associated liver steatohepatitis (MASH). The above results establish phospholipid scrambling at the ER as the lynchpin to maintain a dynamic equilibrium. Considering the requirement of trans-bilayer phospholipid equilibration in numerous biological processes, ranging from catabolic autophagy to viral infection13-16, our study may enable further elucidation of a previously under-appreciated homeostatic control mechanism intrinsic to the ER function in lipid biogenesis and distribution.

cell biology↗

Single-cell multi-omics and spatial multi-omics data integration via dual-path graph attention auto-encoder

Single-cell multi-omics data integration enables joint analysis of the resolution at single-cell level to provide comprehensive and accurate understanding of complex biological systems, while spatial multi-omics data integration is benefit to the exploration of cell spatial heterogeneity to facilitate more diversified downstream analyses. Existing methods are mainly designed for single-cell multi-omics data with little consideration on spatial information, and still have the room for performance improvement. A reliable multi-omics data integration method that can be applied to both single-cell and spatially resolved data is necessary and significant. We propose a single-cell multi-omics and spatial multi-omics data integration method based on dual-path graph attention auto-encoder (SSGATE). It can construct neighborhood graphs based on single-cell expression data and spatial information respectively, and perform self-supervised learning for data integration through the graph attention auto-encoders from two paths. SSGATE is applied to data integration of transcriptomics and proteomics, including single-cell and spatially resolved data of various tissues from different sequencing technologies. SSGATE shows better performance and stronger robustness than competitive methods and facilitates downstream analysis.

bioinformatics↗

Muscone-specific olfactory protein reveals the putative scent-marking pheromone in the Sunda pangolin (Manis javanica)

The Sunda pangolin (Manis javanica) is a burrowing and nocturnal animal, and they have poor vision, thus, intraspecies communication relies on olfaction, such as mating, warning, and scent-marking. However, the intraspecies pheromone in pangolins remains unknown. In this study, all the odorant-binding proteins in Sunda pangolins were functionally expressed, and they were screened against a panel of 32 volatiles that were derived from the pangolins urine, feces, and anal gland secretions. Reverse chemical ecology identified that M. javanica odorant-binding protein 3 (MjavOBP3) possesses the highest binding affinity to muscone. A subsequent behavior-tracking assay showed that only males can sense muscone; thus, we hypothesize that muscone is a male-specific scent-marking pheromone. Meanwhile, the structural study showed that Tyr117 contributes the most to muscones binding, which was further validated by site-directed mutagenesis. The findings clarify the scent-marking mechanism in pangolins, and muscone could potentially be used to support the monitoring and conservation of this endangered animal. Author SummaryThe Sunda pangolin is an endangered mammal that is native to Southeast Asia and is threatened due to its economic value. They are cave-living and nocturnal, poor vision; thus, their intraspecies communication is highly reliant on olfaction. Although they are generally solitary, they have been observed to have some social aspects in the wild, such as breeding and territorial behaviors, which are mediated by scents. However, no previous study has investigated the type of pheromones and how they are detected. Using the reverse chemical ecology approach, MjavOBP3 was found to bind to muscone with high affinity, and behavior-tracking assay was performed under well-controlled artificial rearing conditions, which showed only male pangolins can recognize muscone, suggesting its potential male-specific pheromone role.

zoology↗

Coral hosts actively accumulate inorganic carbon for zooxanthellae to maintain symbiotic relationships

High primary productivity of coral reefs is widely attributed to the mutualistic symbiosis between coral hosts and their microalgal partners (Symbiodiniaceae). Although the mechanisms maintaining this symbiosis have been considerable investigated, how the symbiont microalgae within coral get sufficient CO2 for photosynthesis still remains inadquately explored. Here, we hypothesized that corals may actively accumulate dissolved inorganic carbon (DIC) for microalgae to maintain the symbiosis. Carbon (HCO3- and glucose) supply and consumption were evaluated in the scleractinian coral (Goniopora lobata) and its symbiont under light and dark conditions. Results suggest that Symbiodiniaceae were high DIC consumers, requiring about 2-3 fold more DIC than free-living species. The corals were high DIC producers, with internal concentrations up to 4.2 fold higher than in the surrounding seawater. In the absence of microalgae utilization, the excess DIC they produced appeared detrimental to their own growth. Moreover, transcriptomic analysis identified several DIC enrichment pathways are evolved in corals to attact the Symbiodiniaceae, including CO2 concentrating mechanisms, respiration, calcification and phosphoenolpyruvate carboxylase. Increased the CO2 dosage in seawater may induce coral symbiosis bleaching. Our findings can deeper reveal on the mechanisms sustaining coral symbiosis, and may help to predict how some corals respond to DIC imbalance under climate changes.

ecology↗