Biology subjects

Hu, J.

Publications and source records attributed to Hu, J..

At least 217 records · Page 12Linked to original sources

bioRxiv2024

A novel OsIAA3-OsARF16-OsBUL1 module regulates grain size in rice

Auxin plays an important role in almost every aspect of plant growth and development. However, the molecular mechanism underlying the control of grain size via auxin signaling pathways is still obscure. Here, we reported that the rice Aux/IAA gene OsIAA3 positively regulates grain size by promoting the cell expansion and proliferation of spikelet hulls. OsIAA3 interacted with 11 OsARFs, among which the interaction with OsARF16 was the strongest. Knockout of osarf16 led to smaller grain with decreased grain length, grain width, grain thickness and 1,000-grain weight. Meanwhile, transgenic plants overexpressing OsARF16 produced apparently bigger grain with increased grain length and 1,000-grain weight. Additionally, OsBUL1, which positive regulates grain size by promoting cell expansion is a direct target gene of OsARF16. Results demonstrated that the interaction between OsIAA3 and OsARF16 repressed the transcriptional activation of OsARF16 on OsBUL1. Taken together, our study revealed a novel OsIAA3-OsARF16-OsBUL1 module which regulates grain size, enriching the molecular mechanism of auxin signaling pathway involved in regulating grain size.

genetics↗

bioRxiv2024

Molecular insights into substrate translocation in an elevator-type metal transporter

The Zrt/Irt-like protein (ZIP) metal transporters are key players in maintaining the homeostasis of a panel of essential microelements. The prototypical ZIP from Bordetella bronchiseptica (BbZIP) is an elevator transporter, but how the metal substrate moves along the transport pathway and how the transporter changes conformation to allow alternating access remain to be elucidated. Here, we combined structural, biochemical, and computational approaches to investigate the process of metal substrate translocation along with the global structural rearrangement. Our study revealed an upward hinge motion of the transport domain in a high-resolution crystal structure of a cross-linked variant, elucidated the mechanisms of metal release from the transport site into the cytoplasm and activity regulation by a cytoplasmic metal-binding loop, and unraveled an unusual elevator mode in enhanced sampling simulations that distinguishes BbZIP from other elevator transporters. This work provides important insights into the metal transport mechanism of the ZIP family.

biochemistry↗

bioRxiv2024

MAPK/ERK signaling in gliomas modulates interferon responses, T cell recruitment, enhances tumor-microglia crosstalk, and drives immune checkpoint blockade efficacy.

BackgroundGlioblastoma (GB) remains a formidable challenge in neuro-oncology, with immune checkpoint blockade (ICB) showing limited efficacy in unselected patients. We previously recently established that MAPK/ERK signaling is associated with overall survival following anti-PD-1 and anti-CTLA-4 treatment in recurrent GB. However, the causal relationship between MAPK/ERK signaling and susceptibility to ICB, as well as the mechanisms underlying this association, remain poorly understood. MethodWe conducted in vivo kinome-wide CRISPR/Cas9 screenings in murine gliomas to identify key regulators of susceptibility to anti-PD-1 and CD8+ T cell responses and performed survival studies to validate the most relevant genes. Additionally, paired single cell RNA- sequencing (scRNA-seq) with p-ERK staining, spatial transcriptomics on GB samples, and ex-vivo slice culture of a BRAFV600E mutant GB tumor treated with BRAFi/MEKi were used to determine the causal relationship between MAPK signaling, tumor cell immunogenicity, and modulation of microglia phenotype. ResultsCRISPR/Cas9 screens identified the MAPK pathway, particularly the RAF-MEK-ERK pathway, as the most critical modulator of glioma susceptibility to CD8+ T cells, and anti-PD-1 across all kinases. Experimentally-induced ERK phosphorylation in gliomas enhanced survival with ICB treatment, led to durable anti-tumoral immunity upon re-challenge and memory T cell infiltration in long-term survivors. Elevated p-ERK in glioma cells correlated with increased interferon responses, antigen presentation and T cell infiltration in GB. Moreover, spatial transcriptomics and scRNA-seq analysis revealed the modulation of interferon responses by the MAPK/ERK pathway in BRAFV600E human GB cells with ERK1/2 knockout and in slice cultures of human BRAFV600E GB tissue. Notably, BRAFi/MEKi treatment disrupted the interaction between tumor cells and tumor-associated macrophages/microglia in slice cultures from BRAFV600E mutant GB. ConclusionOur data indicate that the MAPK/ERK pathway is a critical regulator of GB cell susceptibility to anti-tumoral immunity, modulating interferon responses, and antigen-presentation in glioma cells, as well as tumor cell interaction with microglia. These findings not only elucidate the mechanistic underpinnings of immunotherapy resistance in GB but also highlight the MAPK/ERK pathway as a promising target for enhancing immunotherapeutic efficacy in this challenging malignancy.

cancer biology↗

bioRxiv2024

Complete Genomic Characterization of Global Pathogens, Respiratory Syncytial Virus (RSV), and Human Norovirus (HuNoV) Using Probe-based Capture Enrichment.

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in children worldwide, while human noroviruses (HuNoV) are a leading cause of epidemic and sporadic acute gastroenteritis. Generating full-length genome sequences for these viruses is crucial for understanding viral diversity and tracking emerging variants. However, obtaining high-quality sequencing data is often challenging due to viral strain variability, quality, and low titers. Here, we present a set of comprehensive oligonucleotide probe sets designed from 1,570 RSV and 1,376 HuNoV isolate sequences in GenBank. Using these probe sets and a capture enrichment sequencing workflow, 85 RSV positive nasal swab samples and 55 (49 stool and six human intestinal enteroids) HuNoV positive samples encompassing major subtypes and genotypes were characterized. The Ct values of these samples ranged from 17.0-29.9 for RSV, and from 20.2-34.8 for HuNoV, with some HuNoV having below the detection limit. The mean percentage of post-processing reads mapped to viral genomes was 85.1% for RSV and 40.8% for HuNoV post-capture, compared to 0.08% and 1.15% in pre-capture libraries, respectively. Full-length genomes were>99% complete in all RSV positive samples and >96% complete in 47/55 HuNoV positive samples--a significant improvement over genome recovery from pre-capture libraries. RSV transcriptome (subgenomic mRNAs) sequences were also characterized from this data. Probe-based capture enrichment offers a comprehensive approach for RSV and HuNoV genome sequencing and monitoring emerging variants. IMPORTANCERespiratory syncytial virus (RSV) and human noroviruses (HuNoV) are NIAID category C and category B priority pathogens, respectively, that inflict significant health consequences on children, adults, immunocompromised patients, and the elderly. Due to the high strain diversity of RSV and HuNoV genomes, obtaining complete genomes to monitor viral evolution and pathogenesis is challenging. In this paper, we present the design, optimization, and benchmarking of a comprehensive oligonucleotide target capture method for these pathogens. All 85 RSV samples and 49/55 HuNoV samples were patient-derived with six human intestinal enteroids. The methodology described here results has a higher success rate in obtaining full-length RSV and HuNoV genomes, enhancing the efficiency of studying these viruses and mutations directly from patient-derived samples.

molecular biology↗

bioRxiv2024

Spatiotemporal evidence accumulation through saccadic sampling for object recognition

Visual object recognition has been extensively studied under fixation conditions, but our natural viewing involves frequent saccadic eye movements that scan multiple local informative features within an object (e.g., eyes and mouth in a face image). These saccades would contribute to object recognition by subserving the integration of sensory information across local features, but mechanistic models that explain human behavior during natural object recognition have yet to be established due to the presumed complexity of the interactions between the visual and oculomotor systems. Here, we employ a framework of perceptual decision making and show that human face and object categorization behavior with saccades can be quantitatively explained by a model that simply accumulates the sensory evidence available at each moment. Our model can fit human object-recognition behavior even under conditions in which people freely make saccades to scan local features, departing from past studies that required controlled eye movements to test trans-saccadic integration. Moreover, further experimental results confirmed that active saccade commands (efference copy) do not substantially contribute to behavioral performance. Therefore, we propose that object recognition with saccades can be approximated by a parsimonious decisionmaking model without assuming complex interactions between the visual and oculomotor systems.

neuroscience↗

bioRxiv2024

Deep Generative Optimization of mRNA Codon Sequences for Enhanced Protein Production and Therapeutic Efficacy

Messenger RNA (mRNA) therapeutics show immense promise, but their efficacy is limited by suboptimal protein expression. Here, we present RiboDecode, a deep learning framework that generates mRNA codon sequences for enhanced mRNA translation. RiboDecode introduces several advances, including direct learning from large-scale ribosome profiling data and generative exploration of a large sequence space. In silico analysis demonstrates RiboDecode s robust predictive accuracy for unseen genes and cellular environments. In vitro experiments showed substantial improvements in protein expression, significantly outperforming past methods. In addition, RiboDecode enables mRNA design with consideration of cellular context and demonstrates robust performance across different mRNA formats, including m1{Psi}-modified and circular mRNAs, an important feature for mRNA therapeutics. In vivo mouse studies showed that optimized influenza hemagglutinin mRNAs induce ten times stronger neutralizing antibody responses against influenza virus compared to the unoptimized sequence. In an optic nerve crush model, optimized nerve growth factor mRNAs achieve equivalent neuroprotection of retinal ganglion cells at one-fifth the dose of the unoptimized sequence. Collectively, RiboDecode represents a paradigm shift from rule-based to a data-driven, context-aware approach for mRNA therapeutic applications, enabling the development of more potent and dose-efficient treatments.

bioinformatics↗

bioRxiv2024

MorphLink: Bridging Cell Morphological Behaviors and Molecular Dynamics in Multi-modal Spatial Omics

Multi-modal spatial omics data are invaluable for exploring complex cellular behaviors in diseases from both morphological and molecular perspectives. Current analytical methods primarily focus on clustering and classification, and do not adequately examine the relationship between cell morphology and molecular dynamics. Here, we present MorphLink, a framework designed to systematically identify disease-related morphological-molecular interplays. MorphLink has been evaluated across a wide array of datasets, showcasing its effectiveness in extracting and linking interpretable morphological features with various molecular measurements in multi-modal spatial omics analyses. These linkages provide a transparent depiction of cellular behaviors that drive transcriptomic heterogeneity and immune diversity across different regions within diseased tissues, such as cancer. Additionally, MorphLink is scalable and robust against cross-sample batch effects, making it an efficient method for integrative spatial omics data analysis across samples, cohorts, and modalities, and enhancing the interpretation of results for large-scale studies.

bioinformatics↗

bioRxiv2024

Ecosystem stability relies on diversity difference between trophic levels

The stability of ecological communities has a profound impact on humans, ranging from individual health influenced by the microbiome to ecosystem services provided by fisheries. A long-standing goal of ecology is the elucidation of the interplay between biodiversity and ecosystem stability, with some ecologists warning of instability due to loss of species diversity while others arguing that greater diversity will instead lead to instability. Here, by considering a minimal two-level ecosystem with multiple predator and prey species, we show that stability does not depend on absolute diversity but rather on diversity differences between levels. We discovered that increasing diversity in either level first destabilizes but then stabilizes the community (i.e., a re-entrant stability transition). We therefore find that it is the diversity difference between levels that is the key to stability, with the least stable communities having similar diversities in different levels. An analytical stability criterion is derived, demonstrating quantitatively that the critical diversity difference is determined by the correlation between how one level affects another and how it is affected in turn. Our stability criterion also applies to consumer-resource models with other forms of interaction such as cross-feeding. Finally, we show that stability depends on diversity differences in ecosystems with three trophic levels. Our finding of a non-monotonic dependence of stability on diversity provides a natural explanation for the variety of diversity-stability relationships reported in the literature, and emphasizes the significance of level structure in predicting complex community behaviors.

ecology↗

bioRxiv2024

A novel functional coordination in UNC-13 regulates neurotransmitter release

Munc13 plays a crucial role in short-term synaptic plasticity by regulating synaptic vesicle (SV) exocytosis and neurotransmitter release at the presynaptic terminals. However, the intricate mechanisms governing these processes have remained elusive due to the presence of multiple functional domains within Munc13, each playing distinct roles in neurotransmitter release. Here we report a coordinated mechanism in the C. elegans Munc13 homolog UNC-13 that controls the functional switch of UNC-13 during synaptic transmission. Mutations disrupting the interactions of C1 and C2B with diacylglycerol (DAG) and phosphatidylinositol 4,5-bisphosphate (PIP2) on the plasma membrane induced the gain-of-function state of UNC-13L, the long UNC-13 isoform, resulting in enhanced SV release. Concurrent mutations in both domains counteracted this enhancement, highlighting the functional interdependence of C1 and C2B. Intriguingly, the individual C1 and C2B domains exhibited significantly stronger facilitation of SV release compared to the presence of both domains, supporting a mutual inhibition of C1 and C2B under basal conditions. Moreover, the N-terminal C2A and X domains exhibited opposite regulation on the functional switch of UNC-13L. Furthermore, we identified the polybasic motif in the C2B domain that facilitates SV release. Finally, we found that disruption of C1 and C2B membrane interaction in UNC-13S, the short isoform, leads to functional switch between gain-of-function and loss-of-function. Collectively, our findings provide a novel mechanism for SV exocytosis wherein UNC-13 undergoes functional switches through the coordination of its major domains, thereby regulating synaptic transmission and short-term synaptic plasticity.

neuroscience↗

bioRxiv2024

Recycling of trans-Golgi SNAREs is essential for apoplastic effector secretion and effective pathogenicity of Magnaporthe oryzae

Vesicle transport is an essential process that mediates the growth, development and virulence of pathogenic fungi. However, the intricate mechanisms underlying how vesicle transport regulates the secretion of effector proteins remain to be fully elucidated. Here, we unveiled a novel pathway in which retromer and trans-Golgi (TGN) SNARE proteins co-regulate the proper secretion of apoplastic effectors in the rice blast fungus Magnaporthe oryzae. A TGN-associated SNARE complex consisting of MoSnc1, MoTlg1, MoTlg2, and MoVti1 was found to be essential for growth, development and pathogenicity in the fungus. Moreover, the TGN-associated SNARE complex is indispensable for accurate secretion of apoplastic effectors. Furthermore, we have elucidated that the dynamin-like protein MoVps1, an upstream regulator of the retromer complex, regulates the fission of MoVps35-coated vesicle and the proper localization of the TGN-associated SNARE complex. Additionally, we employed prochlorperazine, which identified as a potent dynamin inhibitor, elicits a developmental response in M. oryzae akin to MoVPS1 disruption, highlighting the pivotal regulatory role of dynamin and its potential as a therapeutic target for rice blast disease management. In conclusion, the study uncovered a specific mechanism by which MoVps1 and the retromer complex regulate the positioning of TGN-associated SNARE proteins to effectively promote effector secretion. It provides a deeper understanding of the molecular mechanisms of effector secretion in fungi and underscores the importance of vesicle transport in fungal pathogenesis. ImportanceVesicle transport is essential for pathogenic fungi as it controls the secretion of effectors that modulate interactions with the host and infection processes. The detailed mechanisms of effector secretion via vesicular pathways in these fungi are not yet fully understood. In this study, we have discovered a new regulatory pathway involving the retromer complex and trans-Golgi SNARE proteins that is critical for the proper secretion of apoplast effectors in M. oryzae. We have identified an important TGN-associated SNARE complex, consisting of MoSnc1, MoTlg1, MoTlg2 and MoVti1, which is required for the development and pathogenicity of M. oryzae. Our results emphasize the importance of this SNARE complex for the precise secretion of effectors into the apoplast, a key step in pathogenesis. Additionally, we demonstrated that the dynamin-like protein MoVps1, a protein acting upstream of the retromer complex, is vital for the correct localization of the TGN-associated SNARE complex. Furthermore, our research underscores the critical regulatory role of dynamin in M. oryzae pathogenesis, with prochlorperazine serving as an inhibitor that mimics the phenotypic effects of MoVps1 disruption, thereby highlighting its potential as a biopesticide candidate for rice blast disease management. Our study has uncovered a specific regulatory mechanism in which MoVps1 and the retromer complex control the positioning and function of TGN-associated SNARE proteins, thereby facilitating effector secretion. This work not only advances our understanding of the molecular basis of effector secretion in fungi, but also has implications for the development of novel strategies to control fungal diseases.

microbiology↗

bioRxiv2024

Efficient integration of multiple spatial transcriptomics data for 3D domain detection, matching, and alignment with stMSA

Spatial omics (SO) is a powerful methodology that enables the study of genes, proteins, and other molecular features within the spatial context of tissue architecture. With the growing availability of SO datasets, researchers are eager to extract biological insights from larger datasets for a more comprehensive understanding. However, existing approaches focus on batch effect correction, often neglecting complex biological patterns in tissue slices, complicating feature integration and posing challenges when combining transcriptomics with other omics layers. Here, we introduce stMSA (SpaTial Multi-Slice/omics Analysis), a deep graph contrastive learning model that incorporates graph auto-encoder techniques. stMSA is specifically designed to produce batch-corrected representations while retaining the distinct spatial patterns within each slice, considering both intra- and inter-batch relationships during integration. Extensive evaluations show that stMSA outperforms state-of-the-art methods in distinguishing tissue structures across diverse slices, even when faced with varying experimental protocols and sequencing technologies. Furthermore, stMSA effectively deciphers complex developmental trajectories by integrating spatial proteomics and transcriptomics data, and excels in cross-slice matching and alignment for 3D tissue reconstruction.

bioinformatics↗

bioRxiv2024

PPR767 affects plant architecture and drought resistance by modulating complex I activity and ROS content in rice

The RNA-binding proteins (RBPs) encoded by nucleus are essential for the metabolism of RNAs in eukaryotes. The pentatricopeptide repeat (PPR) proteins, a large subset of RBPs, participate in organellar RNA processing for plant development and reproduction. Here, we identified an E-type PPR protein, PPR767, which functions in mitochondria. Knocking out PPR767 resulted in shorter plant height, thinner stems, shorter and narrower blades, and consequently affected yield traits, compared to those of the wild type. PPR767 primarily participated in the editing of 4 sites, nad1-674, nad3-155, nad3-172, and nad7-317. And PPR767 interplayed with MORF1 and MORF8, suggesting the editosome in rice is complicated. Meanwhile, the activity of mitochondrial complex I was decreased, and the structure of mitochondria was compromised in the mutants. Furthermore, mutation of PPR767 influenced rice drought tolerance and the expression levels of genes involved in the reactive oxygen species (ROS) accumulation. These findings suggest that PPR767 guarantees the complex I activity by properly regulating the RNA editing efficiency of mitochondrial genes and affects drought tolerance by modulating ROS content in rice, providing valuable insights into the mechanisms by which PPRs fulfil their functions.

molecular biology↗

bioRxiv2024

Quantifiable Blood TCR Repertoire Components Associated with Immune Aging

T cell senescence results in decayed adaptive immune protection in older individuals, with decreased or increased abundance of certain T cell phenotypic subpopulations. However, no study has linked aging to the dynamic changes of T cell clones. Through a newly develop computational framework, Repertoire Functional Units (RFU), we investigated over 6,500 TCR repertoire sequencing samples from multiple human cohorts. Our analysis identified age-associated RFUs repeatedly and consistently across different cohorts. Quantification of RFU decreases with aging revealed accelerated loss under immunosuppressive conditions. Systematic analysis of age-associated RFUs in clinical samples manifested a potential link between these RFUs and improved clinical outcomes during acute viral infections, such as lower ICU admission and reduced risk of developing complications. Finally, our investigation of bone-marrow transplantation patients indicated a secondary expansion of the age-associated clones upon receiving stem cells from younger donors. Together, our results suggest the existence of certain clones or a TCR clock that could reflect the immune functions in aging populations.

immunology↗

bioRxiv2024

STK19 is a transcription-coupled repair factor that participates in UVSSA ubiquitination and TFIIH loading.

Transcription-coupled repair (TCR) is the major pathway to remove transcription-blocking lesions. Although discovered for nearly 40 years, the mechanism and critical players of mammalian TCR remain unclear. STK19 is a factor affecting cell survival and recovery of RNA synthesis in response to DNA damage, however, whether it is a necessary component for TCR is unknown. Here we demonstrated that STK19 is essential for human TCR. Mechanistically, STK19 is recruited to damage sites through direct interaction with CSA. It can also interact with RNA polymerase II in vitro. Once recruited, STK19 plays an important role in UVSSA ubiquitination which is needed for TCR. STK19 also promotes TCR independent of UVSSA ubiquitination by stimulating TFIIH recruitment through its direct interaction with TFIIH. In summary, our results suggest that STK19 is a key factor of human TCR that links CSA, UVSSA ubiquitination and TFIIH loading, shedding light on the molecular mechanisms of TCR.

biochemistry↗

bioRxiv2024

Coordination of transcription-coupled repair and repair-independent release of stalled RNA polymerase II in response to transcription-blocking lesions

Transcription-blocking lesions (TBLs) stall elongating RNA polymerase II (PolII), which then initiates transcription-coupled repair (TCR) to remove TBLs and allow transcription recovery. In the absence of TCR, eviction of lesion-stalled PolII is required for alternative pathways to address the damage, but the mechanism is unclear. This study, utilizing Protein-Associated DNA Damage Sequencing (PADD-seq), reveals that the p97-proteasome pathway can evict lesion-stalled PolII independently of repair. Both TCR and repair-independent eviction require CSA and ubiquitination. However, p97 is dispensable for TCR and PolII eviction in TCR-proficient cells, highlighting repairs prioritization over repair-independent eviction. Moreover, ubiquitination of RPB1-K1268 is important for both pathways, with USP7s deubiquitinase activity promoting TCR without abolishing repair-independent PolII release. In summary, this study elucidates the fate of lesion-stalled PolII, and may shed light on the molecular basis of genetic diseases caused by the defects of TCR genes.

molecular biology↗

bioRxiv2024

Pan-cortical cellular imaging in freely behaving mice using a miniaturized micro-camera array microscope (mini-MCAM)

Understanding how circuits in the brain simultaneously coordinate their activity to mediate complex ethnologically relevant behaviors requires recording neural activities from distributed populations of neurons in freely behaving animals. Current miniaturized imaging microscopes are typically limited to imaging a relatively small field of view, precluding the measurement of neural activities across multiple brain regions. Here we present a miniaturized micro-camera array microscope (mini-MCAM) that consists of four fluorescence imaging micro-cameras, each capable of capturing neural activity across a 4.5 mm x 2.55 mm field of view (FOV). Cumulatively, the mini-MCAM images over 30 mm2 area of sparsely expressed GCaMP6s neurons distributed throughout the dorsal cortex, in regions including the primary and secondary motor, somatosensory, visual, retrosplenial, and association cortices across both hemispheres. We demonstrate cortex-wide cellular resolution in vivo Calcium (Ca2+) imaging using the mini-MCAM in both head-fixed and freely behaving mice.

neuroscience↗

bioRxiv2024

Reversible control of kinase signaling through chemical-induced dephosphorylation

The coordination between kinases and phosphatases is crucial for regulating the phosphorylation levels of essential signaling molecules. Methods enabling precise control of kinase activities are valuable for understanding the kinase functions and for developing targeted therapies. Here, we use the abscisic acid (ABA)-induced proximity system to reversibly control kinase signaling by recruiting phosphatases. Using this method, we found that the oncogenic tyrosine kinase BCR::ABL1 can be inhibited by recruiting various cytoplasmic phosphatases. We also discovered that the oncogenic serine/threonine kinase BRAF(V600E), which has been reported to bypass phosphorylation regulation, can be positively regulated by protein phosphatase 1 (PP1) and negatively regulated by PP5. Additionally, we observed that the dual-specificity kinase MEK1 can be inhibited by recruiting PP5. This suggests that bifunctional molecules capable of recruiting PP5 to MEK or RAF kinases could be promising anticancer drug candidates. Thus, the ABA-induced dephosphorylation method enables rapid screening of phosphatases to precisely control kinase signaling.

cancer biology↗

bioRxiv2024

The O-Fucosyltransferase SPINDLY Attenuates Auxin-Induced Fruit Growth by Inhibiting ARF6 and ARF8 binding to Coactivator Mediator Complex in Arabidopsis

The phytohormone auxin plays a pivotal role in promoting fruit initiation and growth upon fertilization in flowering plants. Upregulation of auxin signaling by genetic mutations or exogenous auxin treatment can induce seedless fruit formation from unpollinated ovaries, termed parthenocarpy. Recent studies suggested that the class A AUXIN RESPONSE FACTOR6 (ARF6) and ARF8 in Arabidopsis play dual functions by first inhibiting fruit initiation when complexed with unidentified corepressor IAA protein(s) before pollination, and later promoting fruit growth after fertilization as ARF dimers. However, whether and how posttranslational modification(s) regulate ARF6- and ARF8-mediated fruit growth were unknown. In this study, we reveal that both ARF6 and ARF8 are O-fucosylated in their middle region (MR) by SPINDLY (SPY), a novel nucleocytoplasmic protein O-fucosyltransferase, which catalyzes the addition of a fucose moiety to specific Ser/Thr residues of target proteins. Epistasis, biochemical and transcriptome analyses indicated that ARF6 and ARF8 are downstream of SPY, but ARF8 plays a more predominant role in parthenocarpic fruit growth. Intriguingly, two ARF6/8-interacting proteins, the co-repressor IAA9 and MED8, a subunit of the coactivator Mediator complex, were also O-fucosylated by SPY. Biochemical assays demonstrated that SPY-mediated O-fucosylation of these proteins reduced ARF-MED8 interaction, which led to enhanced transcription repression activity of the ARF6/8-IAA9 complex but impaired transactivation activities of ARF6/8. Our study unveils the role of protein O-fucosylation by SPY in attenuating auxin-triggered fruit growth through modulation of activities of key transcription factors, a co-repressor and the coactivator MED complex.

plant biology↗