Biology subjects

Luo, H.

Publications and source records attributed to Luo, H..

At least 73 records · Page 4Linked to original sources

bioRxiv2024

Sulfur oxidation through rDsr in a novel Sox-free marine Roseobacter lineage

Sulfur oxidation drives nutrient and energy flow in marine sediments. Bacteria typically oxidize thiosulfate, a key sulfur intermediate, either through a complete Sox system or through an incomplete Sox system that feeds zero valent sulfur into the reverse dissimilatory sulfite reductase (rDsr) pathway. Whether rDsr alone can oxidize thiosulfate has been unclear. Here we show that ten intertidal Ruegeria strains carry a complete rDsr pathway but lack all sox genes. Under low oxygen (2% O2) but not under air, thiosulfate activates the pathway, enhances growth, and is associated with accelerated nitrate reduction. Using a CRISPR base editing tool for Ruegeria, we demonstrate that disrupting dsrA, which encodes a subunit of the core rDsr enzyme, significantly delays thiosulfate consumption, suggesting that rDsr is actively involved in oxidation. Previous work only documented rDsr acting downstream of an incomplete Sox system; our results establish that a standalone rDsr pathway is sufficient for thiosulfate consumption under oxygen limitation and that this activity can feed electrons into the denitrification pathway. Metagenomic surveys show rDsr genes from this group are widespread in low oxygen marine environments, including coastal sediments where they account for up to 26% of all rDsr genes. These findings revise the view that thiosulfate oxidation depends on Sox and highlight rDsrs ecological role in deoxygenated habitats.

ecology↗

bioRxiv2024

Brain-derived exosomal hemoglobin transfer contributes to neuronal mitochondrial homeostasis under hypoxia

Hypoxia is an important physiological stress causing nerve injuries and several brain diseases. However, the mechanism of brain response to hypoxia remains unclear, thus limiting the development of interventional strategies. This study conducted combined analyses of single-nucleus transcriptome sequencing and extracellular vesicle transcriptome sequencing on hypoxic mouse brains, described cell-cell communication in the brain under hypoxia from intercellular and extracellular dimensions, confirmed that hemoglobin mRNA was transferred from non-neuronal cells to neurons, and eventually expressed. Then we further explored the role of exosomal hemoglobin transfer in vitro, clarified that hypoxia promoted the transfer and expression of exosomal hemoglobin between endothelial cells and neurons. And we found the vital function of exosomal hemoglobin to protect against neurological injury by maintaining mitochondrial homeostasis in neurons. In conclusion, this study identified a novel mechanism of mutual aid in hypoxia responses in the brain, involving exosomal hemoglobin transfer, clarified the important role of exosomal communication in the process of brain stress response, and provided a novel interventional perspective for hypoxia-related brain diseases.

cell biology↗

bioRxiv2024

New isolates refine the ecophysiology of the Roseobacter CHAB-I-5 lineage

The CHAB-I-5 cluster is a pelagic lineage that can comprise a significant proportion of all roseobacters in surface oceans and have predicted roles in biogeochemical cycling via heterotrophy, aerobic anoxygenic photosynthesis (AAnP), CO oxidation, DMSP degradation, and other metabolisms. Though cultures of CHAB-I-5 have been reported, none have been explored and the best known representative, strain SB2, was lost from culture after obtaining the genome sequence. We have isolated two new CHAB-I-5 representatives, strains US3C007 and FZCC0083, and assembled complete, circularized genomes with 98.7% and 92.5% average nucleotide identities with the SB2 genome. Comparison of these three with 49 other unique CHAB-I-5 metagenome-assembled and single-cell genomes indicated that the cluster represents a genus with two species, and we identified subtle differences in genomic content between the two species subclusters. Metagenomic recruitment from over fourteen hundred samples expanded their known global distribution and highlighted both isolated strains as representative members of the clade. FZCC0083 grew over twice as fast as US3C007 and over a wider range of temperatures. The axenic culture of US3C007 occurs as pleomorphic cells with most exhibiting a coccobacillus/vibrioid shape. We propose the name Thalassovivens spotae, gen nov., sp. nov. for the type strain US3C007T.

microbiology↗

bioRxiv2024

Nicotine Ameliorates α-synuclein Pre-formed Fibril-Induced Behavioral Deficits and Pathological Features in Mice

BackgroundEpidemiologic study suggests nicotine reduces risk of PD, could be potential treatment for Parkinsons disease. ObjectiveTo study the effect of nicotine on behavioral phenotypes and pathological characteristics of mice induced by human alpha-synuclein preformed fibers (-syn-PFF). MethodsMice were injected with 5 g of human -syn-PFF in the hippocampus while administering nicotine-containing drinking water (200g/mL). After 1 month, the motor ability, mood, spatial learning, and memory ability of the Parkinsons disease(PD)phenotype-like model were detected using open field, rotarod, Y maze, and O maze tests. The expression of pathological -syn, apoptotic proteins and the numbers of glial cells and neural stem cells in the hippocampus of mice were detected using western blotting and immunofluorescence. ResultsNicotine significantly reduced pathological -syn accumulation, -syn serine 129 phosphorylation and cell death caused by PFF injection in the hippocampus of mice, inhibited the increase of glial, microglia and apoptotic cells, decreased the expression levels of PI3K and Akt. ConclusionsNicotine may have inhibitory effects on human -syn-PFF-induced neuroinflammation and apoptosis. Thus, it reduces human -syn-PFF-induced behavioral deficits and pathological changes in mice.

animal behavior and cognition↗

bioRxiv2024

Post-transcriptional regulatory pre-complex assembly drives timely cell-state transitions during differentiation

Complexes that control mRNA stability and translation promote timely cell-state transitions during differentiation by ensuring appropriate expression patterns of key developmental regulators. The Drosophila RNA-binding protein Brain tumor (Brat) promotes degradation of target transcripts during the maternal-to-zygotic transition in syncytial embryos and in uncommitted intermediate neural progenitors (immature INPs). We identified Ubiquitin-specific protease 5 (Usp5) as a Brat interactor essential for the degradation of Brat target mRNAs in both cell types. Usp5 promotes Brat-dedadenylase pre-complex assembly in mitotic neural stem cells (neuroblasts) by bridging Brat and the scaffolding components of deadenylase complexes lacking their catalytic subunits. The adaptor protein Miranda binds the RNA-binding domain of Brat, limiting its ability to bind target mRNAs in mitotic neuroblasts. Cortical displacement of Miranda activates Brat-mediated mRNA decay in immature INPs. We propose that the assembly of an enzymatically inactive and RNA-binding-deficient pre-complex poises mRNA degradation machineries for rapid activation driving timely developmental transitions.

developmental biology↗

bioRxiv2024

Meta-transcriptomic analysis of companion animal infectomes reveals their diversity and potential roles in animal and human disease

Companion animals such as cats and dogs harbor diverse microbial communities that can potentially impact human health due to close and frequent contact. To better characterize their total infectomes and assess zoonotic risks, we performed meta-transcriptomic profiling on 239 samples from cats and dogs collected across China, comparing the similarities and differences between animal species (cats or dogs), sampling sites (rectal or oropharyngeal), and health status (healthy or diseased). We identified 24 viral species, 270 bacterial genera, and two fungal genera, including many known pathogens such as canine parvovirus, Clostridium difficile, and Candida albicans, as well as opportunistic pathogens such as canine vesivirus. Microbial compositions differed mainly according to sampling site (i.e., rectal and oropharyngeal swabs), and less so between host species and health status. Notably, we detected 27 potential zoonotic pathogens, such as alphacoronavirus 1, among all sampling sites, hosts, and health status, underscoring substantial zoonotic risks requiring surveillance. Overall, our meta-transcriptomic analysis reveals a landscape of actively transcribing microorganisms in major companion animals, including key pathogens, those with the potential for cross-species transmission, and possible zoonotic threats.

microbiology↗

bioRxiv2024

Let-7i-5p regulates osteogenic differentiation of bone marrow mesenchymal stem cells induced by psoralen by targeting CKIP-1

AbstractPrevious studies have shown that psoralen can treat osteoporosis by inducing osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). CKIP-1 is an inhibitor of bone formation and plays a negative regulatory role in the osteogenic differentiation of BMSCs. MicroRNA (miRNA) is a kind of small single-stranded non-coding RNA, which regulates the occurrence and development process of cell proliferation, apoptosis, differentiation and metabolism. Studies have shown that miRNA can affect the proliferation and differentiation of BMSCs by targeting and regulating the expression of related genes. However, whether microRNA can regulate psoralen-induced osteogenic differentiation and its specific mechanisms remain unclear. The aim of this study was to identify miRNA target genes regulating the osteogenic differentiation of BMSCs induced by psoralen and further analyze the mechanism.miRNA microarray was performed to screen the differentially expressed mirnas induced by psoralen, and bioinformatics analysis and luciferase reporter gene assay were used to determine the target sites of let-7i-5p. The mechanism of let-7i-5p in psoralen induced osteogenic differentiation of BMSCs was investigated using in vitro overexpression or inhibition approaches.The results showed that miRNA microarray analysis and reverse transcription quantitative PCR further confirmed that let-7i-5p was up-regulated during the process of psoralin-induced osteogenic differentiation of BMSCs.Bioinformatics analysis and luciferase reporter gene assay confirmed CKIP-1 as a potential target of let-7i-5p.Overexpression of CKIP-1 by transfection with CKIP-1 mimetic significantly inhibited the expression of BMP, Runx2, and Smad1, while CKIP-1 inhibitor promoted their expression.Overexpression of let-7i-5p partially relieved the inhibitory effect of CKIP-1 on osteogenic differentiation of BMSCs.Our results suggest that let-7i-5p regulates psoralen-induced osteogenic differentiation of BMSCs by targeting CKIP-1, which provides a new therapeutic target for osteoporosis.

genetics↗

bioRxiv2024

CMTM6 maintains B cell intrinsic CD40 expression to regulate anti-tumor immunity

HighlightsO_LIB cells participate in anti-tumor immunity by influencing the intratumoral infiltration and function of T cells; C_LIO_LICMTM6 cis-interacts with CD40 and inhibits ubiquitin/proteasome-mediated CD40 degradation to maintain CD40 cell membrane levels; C_LIO_LILoss of B cell-intrinsic CMTM6 significantly reduces CD40 signaling-mediated B cell activation, survival, differentiation, T/B cell interaction and anti-tumor immunity; C_LIO_LIB cell-intrinsic CMTM6 deficiency leads to a significant reduction in the anti-tumor activity CD40 agonists and ICB therapy. C_LI In BriefLong et al. demonstrate that B-cell intrinsic CMTM6 regulates CD40 signaling and function via maintaining the cell membrane level of B-cell CD40 through ubiquitin-proteasome pathway inhibition, thereby affecting B cell function, anti-tumor B-cell immunity and the efficacy of CD40 agonist and ICB therapy. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=137 SRC="FIGDIR/small/583639v2_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@7639cdorg.highwire.dtl.DTLVardef@1ccddaaorg.highwire.dtl.DTLVardef@ecc9f3org.highwire.dtl.DTLVardef@1be8cb0_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphic AbstractsC_FLOATNO C_FIG The essential role of B cells and B cell intrinsic molecules in tumor immunity is beginning to be recognized. Tumor cell CMTM6 is a novel tumor immunoregulator involved in maintaining membrane levels of several important molecules, such as PD-L1 and CD58. Host CMTM6 may also play a function in the tumor microenvironment. Here, we found that CMTM6 was highly expressed in splenic B cells and tumor-infiltrating B cells. CMTM6 deficiency resulted in impaired splenic development, germinal center B cell differentiation, memory B cell differentiation, T/B cell interaction and B cell anti-tumor immune responses. Through multi-omics data mining and B-cell agonist screening, we identified that CMTM6 interacted with CD40 and maintained CD40 membrane levels in B cells. CMTM6 cis-interacts with CD40 and inhibits ubiquitin/proteasome-mediated CD40 degradation. CMTM6 deficiency led to impaired CD40 signaling-mediated B cell activation, survival, proliferation, differentiation and T/B cell interaction. In vivo, CMTM6 deficiency leads to a significant decrease in the anti-tumor activity of ICB therapy and B cell-dependent CD40 agonists. Collectively, B-cell intrinsic CMTM6 maintains B cell CD40 levels and signaling to promote B cell function and anti-tumor immunity.

immunology↗

bioRxiv2024

Reactivated past decisions repel early sensory processing and attract late decision-making

Automatic shaping of perception by past experiences is common in many cognitive functions, reflecting the exploitation of temporal regularities in environments. A striking example is serial dependence, i.e., current perception is biased by previous trials. However, the neural implementation of its operational circle in human brains remains unclear. In two experiments with Electroencephalography (EEG) / Magnetoencephalography (MEG) recordings and delayed-response tasks, we demonstrate a two-stage repulsive-then-attractive past-present interaction mechanism underlying serial dependence. First, past-trial reports serve as a prior to be reactivated during both encoding and decision-making. Crucially, past reactivation interacts with current information processing in a two-stage manner: repelling and attracting the present during encoding and decision-making, and arising in the sensory cortex and prefrontal cortex, respectively. Finally, while the early stage occurs automatically, the late stage is modulated by task and predicts bias behavior. Our findings might also illustrate general mechanisms of past-present influences in neural operations.

neuroscience↗

bioRxiv2024

Dating ammonia-oxidizing bacteria with abundant eukaryotic fossils

Evolution of a complete nitrogen cycle relies on the onset of ammonia oxidation, which aerobically converts ammonia to nitrogen oxides. However, accurate estimation of the antiquity of ammonia-oxidizing bacteria (AOB) remains challenging because AOB-specific fossils are absent and bacterial fossils amenable to calibrate bacterial molecular clocks are rare. Leveraging the ancient endosymbiosis of mitochondria and plastid, as well as using state-of-the-art techniques such as the Bayesian sequential dating approach, we obtained a robust timeline of AOB evolution calibrated by fossil-rich eukaryotic lineages. We show that the first AOB evolved in marine Gammaproteobacteria (Gamma-AOB) and emerged between 2.1 and 1.9 billion years ago (Ga), thus postdating the Great Oxidation Event (GOE; 2.4-2.32 Ga). To reconcile the sedimentary nitrogen isotopic signatures of ammonia oxidation occurring near the GOE, we propose that ammonia oxidation likely occurred at the common ancestor of Gamma-AOB and Gammaproteobacterial methanotrophs, or the actinobacterial/verrucomicrobial methanotrophs, which are known to have ammonia oxidation activities. We also do not rule out another possibility that nitrite was transported from the terrestrial habitats where ammonia oxidation by archaea likely took place. Further, we show that the Gamma-AOB predates the anaerobic ammonia oxidizing (anammox) bacteria which also emerged in marine environments, implying that the origin of ammonia oxidation constrained the origin of anammox as nitrite produced by the former fuels the latter. Our robustly calibrated molecular clocks support a new hypothesis that nitrogen redox cycle involving nitrogen oxides evolved rather late in the ocean.

molecular biology↗

bioRxiv2024

2-D Neural Geometry Underpins Hierarchical Organization of Sequence in Human Working Memory

Working memory (WM) is constructive in nature. Instead of passively retaining information, WM reorganizes complex sequences into hierarchically embedded chunks to overcome capacity limits and facilitate flexible behavior. To investigate the neural mechanisms underlying hierarchical reorganization in WM, we performed two electroencephalography (EEG) and one magnetoencephalography (MEG) experiments, wherein humans retain in WM a temporal sequence of items, i.e., syllables, which are organized into chunks, i.e., multisyllabic words. We demonstrate that the 1-D sequence is represented by 2-D neural representational geometry in WM arising from parietal-frontal regions, with separate dimensions encoding item position within a chunk and chunk position in the sequence. Critically, this 2-D geometry is observed consistently in different experimental settings, even during tasks discouraging hierarchical reorganization in WM and correlates with WM behavior. Overall, these findings strongly support that complex sequences are reorganized into factorized multi-dimensional neural representational geometry in WM, which also speaks to general structure-based organizational principles given WMs involvement in many cognitive functions.

neuroscience↗

bioRxiv2024

The BioRECIPE Knowledge Representation Format

AO_SCPLOWBSTRACTC_SCPLOWThe BioRECIPE (Biological system Representation for Evaluation, Curation, Interoperability, Preserving, and Execution) knowledge representation format was introduced to facilitate seamless human-machine interaction while creating, verifying, evaluating, curating, and expanding executable models of intra- and intercellular signaling. This format allows a human user to easily preview and modify any model component, while it is at the same time readable by machines and can be processed by a suite of model development and analysis tools. The BioRECIPE format is compatible with multiple representation formats, natural language processing tools, modeling tools, and databases that are used by the systems biology community. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=117 SRC="FIGDIR/small/579694v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@76a130org.highwire.dtl.DTLVardef@505cb4org.highwire.dtl.DTLVardef@1f64e68org.highwire.dtl.DTLVardef@195bd03_HPS_FORMAT_FIGEXP M_FIG C_FIG

systems biology↗

bioRxiv2024

A neutral process of genome reduction in marine bacterioplankton

Marine bacterioplankton communities are dominated by cells equipped with small genomes. Streamlining selection has been accepted as the main force driving their genome reduction. Here, we report that a neutral evolutionary mechanism governs genome reduction in the Roseobacter group that represents 5-20% of the bacterioplankton cells in coastal waters. Using representative strains that fall into three genome size groups (2-3, 3-4, and 4-5 Mbp), we measured their genomic mutation rates () through long-term mutation accumulation experiments followed by genome sequencing the resulting 437 mutant lines. We further calculated their effective population sizes (Ne) based on and the neutral genetic diversity of the studied species, the latter estimated based on multiple genome sequences of natural isolates collected from global oceans with their population structure considered. A surprising finding is that Ne scales positively with genome size, which is the opposite of the expectation from the streamlining selection theory. As the strength of random genetic drift is the inverse of Ne, this result instead suggests drift as the primary driver of genome reduction. Additionally, we report a negative scaling between and genome size, which is the first experimental evidence for the long-lasting hypothesis that mutation rate increases play a part in marine bacterial genome reduction. As scales inversely with Ne, genetic drift appears to be the ultimate cause of genome reduction in these Roseobacters. Our finding discounts, but is insufficient to reject, the streamlining theory because streamlining process is expected to be more effective in oligotrophic open ocean waters.

microbiology↗

bioRxiv2024

Comparison and Evaluation of Neutralization of Clinically Frequently Used Antimicrobial Agents Using Three Different Culture Media in Simulated Blood Cultures

The performance of BACT/ALERT FA/FN Plu (France) blood culture containing a novel resin, DL (China) blood culture containing common resin, and adsorbent-free Thermo (USA) blood culture relying on dilution for antimicrobial neutralization at %peak serum concentration was evaluated by measuring the recovery of organisms and time to detection (TTD) in nine simulated microorganism-antimicrobial combination blood cultures.There was a significant difference in recovery rates between the aerobic media: 35/40 (87.5%) for BACT/ALERT media, 15/35 (42.9%) for DL media, and 5/40 (12.5%) for Thermo media; whereas, there was no statistical difference in TTD between FA Plus media and DL aerobic media. The recovery rates of the anaerobic media were 32/35 (91.4%) for BACT/ALERT media, 1/35 (2.9%) for DL media, and 5/35 (14.3%) for Thermo media, with significant differences only between BACT/ALERT FN Plus media and the others. Among the seven main antimicrobial categories, only BACT/ALERT FA/FN Plus culture media showed high recovery of microorganisms, except for carbapenems. The DL culture media exhibited a relatively high recovery rate of piperacillin/tazobactam, levofloxacin, and gentamicin only in aerobic media, and Thermo media only displayed the recovery of gentamicin.BACT/ALERT FA/FN Plus culture media with novel resin showed absolute advantages over DL and Thermo culture media and, thus, can be selectively applied clinically with prior use of antimicrobials before pathogen detection. DL culture media containing common resin outperformed adsorbent-free dilution-based Thermo culture media, which can be a backup option. We should focus on improving the neutralization of carbapenems with low efficiency in all three media.

microbiology↗

bioRxiv2024

A Novel Mouse Model for LAMA2-Related Muscular Dystrophy: Analysis of Molecular Pathogenesis and Clinical Phenotype

Our understanding of the molecular pathogenesis of LAMA2-related muscular dystrophy (LAMA2-MD) requires improving. Here, we report the phenotype, neuropathology and transcriptomics data (scRNA-seq and bulk RNA-seq) of a new Lama2 knockout mouse (dyH/dyH) which was created based on the human LAMA2-MD mutation hotspot region using CRISPR-Cas9. The dyH/dyH mice presented severe phenotype with muscular dystrophy. Mouse brain scRNA-seq showed that Lama2 gene was expressed predominantly and specifically in vascular and leptomeningeal fibroblasts and vascular smooth muscle cells, and weakly in astrocytes in wild-type mouse. Laminin 2 expression on the cortical surface was observed with immunofluorescence. In dyH/dyH, Lama2 expression was decreased in those cell types, which might be associated with the disruption of gliovascular basal lamina assembly. Additionally, transcriptomic investigation of muscles showed 2020 differentially expressed genes, mainly associated with the impaired muscle cytoskeleton and development. In summary, this study provided potentially useful information for understanding the molecular pathogenesis of LAMA2-MD.

neuroscience↗

bioRxiv2024

TEMINET: A Co-Informative and Trustworthy Multi-Omics Integration Network for Diagnostic Prediction

Advancing the domain of biomedical investigation, integrated multi-omics data have shown exceptional performance in elucidating complex human diseases. However, as the variety of omics information expands, precisely perceiving the informativeness of intra- and inter-omics becomes challenging due to the intricate interrelations, thus posing significant obstacles in multi-omics data integration. To address this, we introduce a novel multi-omics integration approach, referred to as TEMINET. This approach enhances diagnostic prediction by leveraging an intra-omics co-informative representation method and a trustworthy learning strategy used to address inter-omics fusion. Considering the multifactorial nature of complex diseases, TEMINET utilizes intra-omics features to construct disease-specific networks, then applies graph attention networks and a multi-level framework to capture more collective informativeness than pairwise relations. To perceive the contribution of co-informative representations within intra-omics, we design a trustworthy learning strategy to identify the reliability of each omics in integration. To integrate inter-omics information, a combined beliefs fusion approach is deployed to harmonize the trustworthy representations of different omics types effectively. Our experiments across four different diseases using mRNA, methylation, and miRNA data demonstrate that TEMINET achieves advanced performance and robustness in classification tasks.

bioinformatics↗

bioRxiv2023

LLPS condensates of Fha initiate the inside-out assembly of the type VI secretion system

The type VI secretion system (T6SS) is one of the most powerful nanomachines employed by Gram-negative pathogens for penetrating diverse cell envelopes, including bacteria and fungi, to deliver potent effectors into target cells. While the membrane-anchored contractile tubular structure of the T6SS is well characterized, the assembly process remains poorly understood. The prevailing model suggests that the assembly of T6SS initiates from its outer-membrane component. Here, we report a distinct model that the cytoplasmic protein Fha initiates T6SS assembly in Acidovorax citrulli, an important plant pathogen. Fha dictates the formation of the inner-membrane complex and the baseplate, and directly interacts with these key components. Importantly, imaging and biochemical assays reveal that Fha undergoes liquid-liquid phase separation (LLPS), forming condensates that selectively recruit essential T6SS proteins, which are otherwise dispersed in cells. Fha also exhibited conserved functions in human pathogens Vibrio cholerae and Pseudomonas aeruginosa. These findings unveil an inside-first LLPS-driven model for T6SS assembly and suggest LLPS might be broadly involved in mediating the assembly of bacterial macromolecular complexes and facilitating interspecies interactions and pathogenesis. Significance statementThe T6SS plays a pivotal role in interspecies competition and host-microbe interactions by delivering toxins to various prokaryotes and eukaryotes. Its crucial function relies on a membrane-anchored macromolecular structure comprising at least 13 conserved components. However, the mechanisms governing the efficient assembly of its diverse cytosolic and membrane-bound components remain elusive. Here, we identify Fha, a conserved cytosolic protein, as a key initiator of T6SS assembly. Fha recruits multiple structural and effector components, forming LLPS condensates. Fha homologs of plant and human pathogens exhibit conserved functions. Our findings not only unveil an inside-first assembly model for the T6SS, initiating from inner-membrane and baseplate components, but also suggest LLPS may have a broader impact on bacterial physiology beyond intracellular activities.

microbiology↗

bioRxiv2023

Hummingbirds rapidly respond to the removal of vision and control a sequence of rate-commanded maneuvers in milliseconds

Hummingbird flight is the epitome of extreme aerial agility and controlled stability, as hummingbirds routinely exercise a variety of stunning aerobatic feats. Yet, the control of these amazing maneuvers is not well understood. Here we examined how hummingbirds control a sequence of maneuvers within milliseconds and tested whether and when their vision is active during this rapid process. We elicited escape flight in calliope hummingbirds and removed visible light at various instants during the maneuvers and quantified their flight kinematics and responses. We show that the escape maneuvers were composed of rapidly-controlled sequential modules, including evasion, reorientation, nose-down dive, forward flight, and nose-up to hover. The hummingbirds did not respond to the light removal during evasion and reorientation until a critical light-removal time; afterward they showed two categories of luminance-based responses that rapidly altered maneuvering modules to terminate the escape. We also show that hummingbird maneuvers are rate-commanded and require no active braking, i.e., their body angular velocities were proportional to the change of wing motion patterns, a trait that likely alleviates the computational demand on flight control. Together, this work uncovers the key traits of hummingbird agility, which can also inform and inspire designs for next-generation agile aerial systems.

animal behavior and cognition↗