Soil salinization constrains crop yield and ecological restoration. Endophytic bacteria can promote plant growth and enhance tolerance to abiotic stresses. Using salt-sensitive cucumber as a model, we systematically evaluated six endophytic bacterial strains for salt-tolerance, including Pseudomonas fulva PY-1, Kosakonia cowanii Cya-1, Bacillus stercoris Cya-2, Serratia marcescens QP-1, Raoultella terrigena Ma-1 and Novosphingobium capsulatum Ly-1, and investigated their potential mechanisms in alleviating salt-induced damage. All six bacterial strains were able to tolerate high salinity (1 mol/L NaCl) in vitro and significantly mitigated salt stress damage to cucumber seedlings under 250 mmol/L NaCl. Multi-omics analysis (microbiome, transcriptome, and metabolome) revealed that these strains influenced the rhizosphere microecological niche, leading to increasing abundance of salt-tolerant microbial taxa and the establishment of a stress-resilient community structure. For example, in the Cya-2 treatment group, the relative abundance of the genus Pseudomonas increased by an average of 5.87

The circadian clock not only coordinates plant growth with daily environmental changes but also interacts with endogenous hormonal pathways, such as abscisic acid (ABA) signaling, to balance growth and abiotic stress responses. Although the feedback network between the circadian system and ABA pathway has been well-established, the regulatory relationship between the ABA receptor PYRABACTIN RESISTANCE 1-LIKE (PYLs) family and the clock remains largely unclear, and the understanding of how ABA signaling feeds back to modulate the clock is still limited. Here, we show that the null mutants of TIME FOR COFFEE (TIC) and CIRCADIAN CLOCK ASSOCIATED 1/ LATE ELONGATED HYPOCOTYL (CCA1/LHY), which are core components of circadian Morning Complex (MC), display hypersensitivity to ABA during seed germination. Mechanistically, the MC could directly bind to the promoters of PYL4, PYL5 and PYL6 to repress their transcription at dawn, which may contribute to the attenuation of ABA signal transduction. Furthermore, ABA could induce TIC expression, and TIC is required for transferring ABA signals into coherent circadian rhythm. Taken together, these findings suggest that the MC may function as a dawn-specific integrator, linking ABA signaling with the circadian core oscillator, hence offering new insights into how plants coordinate hormonal and temporal regulation.

Titanium ions can significantly promote plant growth and increase crop yield, yet the underlying mechanism remains an enigma. This study investigated the effect of titanium ions on tomato (Solanum lycopersicum) by foliar spraying and root irrigation with titanium ion solution (8 mg/L) in both pot and field trials. Pot and field trials showed that exogenous titanium ions significantly stimulated plant growth and root system development, enhanced antioxidant capacity, alleviated Blossom end rot and saline-alkali stress. After 24 h foliar application, comparative RNA-Seq profiling of leaves identified 4,214 differentially expressed genes. GO and KEGG enrichment analyses revealed that titanium ions affected core pathways such as DNA replication, protein translation, phenylpropanoid biosynthesis, plant-pathogen interaction, and plant hormone signal transduction in tomato. Notably, virtually all the genes associated with DNA replication and ribosome translation were remarkably upregulated. Other important upregulated genes included the phytohormone related genes (e.g., auxin, ethylene and gibberellin) and stress-related transcription factor genes (e.g., MYB13, WRKY46, WRKY51, WRKY54, PLT2, ANT, and CRF2). The qRT-PCR validated the RNA-Seq results with high concordance. This study partially elucidates the mechanisms by which titanium ions promote plant growth and enhance abiotic stress resilience, providing guidance for the application of titanium ion-based biostimulants in agricultural production.

Herpetospermum pedunculosum (Cucurbitaceae) is a dioecious species whose seeds from female individuals are highly valued for their hepatoprotective properties. However, the industrial cultivation is severely constrained by the low natural feminization rate and the absence of reliable sex-determination markers at the seedling stage. Here, through ND-FISH, multi-omics and PCR technique, we find that: (i) H. pedunculosum is diploid ( 2n = 20) and probably has a heterogametic male system (XX/XY); (ii)A 241-kb sex-determining region (SDR01) harbors several candidate sex-determining loci, located at the end of pseudochromosome Chr01, including the MADS-box transcription factor HpAP3 and genes involved in phytohormone metabolism and signaling; (iii) The auxin-responsive gene HpSAUR50 in SDR01 is strictly present only in female individuals. Our results indicate that phytohormones, particularly ethylene and auxin, are integral to sex determination in H.pedunculosum, and that HpSAUR50 functions as a reliable molecular marker for the early sex detecting.

We revealed essential roles of GmCDC7 in modulating seed size/weight and seed protein/oil content in soybean, presenting potential new targets for improving yield and quality of soybean and other crops. Seed size/weight is a critical factor determining crop yield; however, a limited number of genes regulating this trait have been characterized in soybean. In this study, we identified a Glycine max CELL DIVISION CYCLE 7 (GmCDC7) and revealed its essential roles in seed development. The putative GmCDC7 was highly conserved in both sequences and structure across various species. GmCDC7 transcripts were detectable in multiple tissues, with peak expression occurring during early seed development, while the GmCDC7 proteins were predominantly localized within the nucleus. CRISPR/Cas9-mediated knockout of GmCDC7 led to a significant increase in seed size and 100-seed weight, while overexpression of this gene resulted in a reduction in both seed size and weight. Further cytological analysis demonstrated that GmCDC7 promoted cell expansion and inhibited cell proliferation in seeds. Notably, the gene-edited gmcdc7 mutants showed a substantial increase in protein content alongside a reduction in oil content in seeds. Correspondingly, transcriptomic analyses revealed that GmCDC7 may significantly influence multifaceted regulatory pathways related to cell cycle-related activities, storage protein accumulation, and lipid transport and metabolism during seed development. These findings suggest that GmCDC7 plays pivotal roles in modulating seed size/weight and quality, offering new gene resources and insights into biotechnological strategies for soybean breeding.

【Objective】This study elucidated the antifungal rate and mechanism of lipopeptide extracts from Bacillus amyloliquefaciens against Alternaria alternata in tomatoes, aiming to provide scientific basis for green control of black spot disease in tomatoes.【Method】A alternata, the dominant pathogen of tomato black spot, was taken as the research object. The antifungal mechanism of B. amyloliquefaciens lipopeptide extract on A. alternata was investigated through in-dish antifungal test, scanning electron microscope (SEM) observation test, in vitro fruit test and transcriptomic analysis.【Result】In-dish antifungal test showed that the inhibition rate of B. amyloliquefaciens lipopeptide extract on the growth of A. alternata colony was 56.00% and the inhibition rate on mycelium biomass was 60.14% on the seventh day of culture. SEM showed that lipopeptide extracts treatment could lead to distortion and collapse of A. alternata mycelium and spores. In vitro fruit test showed that the diameter of tomato black spot disease lesion decreased by 89.97% after inoculation with lipopeptide extract. Compared with the control group, the incidence of black spot decreased from 17.94% to 6.25%, and the control effect of black spot disease was 65.16%. Transcriptome sequencing was performed on A. alternata mycelium treated with lipopeptide extract and untreated, and the differential genes of MAPK signaling pathway and glycolysis/gluconeogenesis signaling pathway were analyzed, respectively. And it was found that the gene encoding Ras homologous gene family A (Rho1) was significantly up-regulated. The genes encoding protein Ste50, glucose-6-phosphatase, hexokinase, pyruvate carboxylase and 6-phosphofructokinase were significantly down-regulated. These up-regulated and down-regulated genes may be the key genes related to the inhibition of A. alternata growth by lipopeptide extract.【Conclusion】The lipopeptide extract can inhibit the growth of A. alternata by destroying spore and mycelium structure and regulating the expression of key genes.

The plant circadian clock coordinates internal processes with daily and seasonal environmental changes by interacting with prevalent light cues. However, how the circadian clock feedback regulates light signals remains largely elusive. Here, we identify that the clock regulator TIME FOR COFFEE (TIC), which interacts with the core clock components CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) to form a "Morning Complex" in the nucleus and co-repress numerous genes, particularly at dawn. Intriguingly, the MC inhibits PHYA and other phyA signaling components at dawn through binding to their promoters. Mutants lacking CCA1 and LHY show increased sensitivity to far-red light, similar to tic mutants, highlighting the cooperative role of TIC, CCA1, and LHY in regulating light-inhibited hypocotyl growth. Altogether, these findings indicate that the circadian MC is a key complex, feedback regulates light signal and mediates multiple biological processes at dawn to ensure plant fitness.

Poa crymophila is a perennial herbaceous plant of the Poaceae family that is adapted to high-altitude environments of Qinghai-Tibet Plateau, exhibiting outstanding cold and drought tolerance. Transcriptomic analyses have indicated that the transcription factor gene CL14612.Contig2_DB in P. crymophila is significantly upregulated in response to both low-temperature and drought stress. Genomic and homology analysis has identified CL14612.Contig2_DB as the transcription factor PcNAC2, which has a total gene length of 1084 bp with a coding sequence of 981 bp, including one intron and two exons. To elucidate its function, we cloned PcNAC2 cDNA and introduced it into tobacco plants (Nicotiana tabacum and Nicotiana benthamiana). The results demonstrated that the heterologous expression of PcNAC2 markedly enhanced the tolerance to chilling, freezing, osmotic, and salt stress in the transgenic tobacco. Under stress conditions, the transgenic tobacco exhibited more developed root systems and superior growth compared to wild-type plants, and was able to recover rapidly after stress relief. This study presents the pivotal role of PcNAC2 in mediating multiple abiotic stress responses and provides a valuable genetic resource for the breeding of stress-tolerance forage grasses or other crops in high-altitude environments.

Poa crymophila, a perennial Poaceae species native to the Qinghai-Tibet Plateau, exhibits remarkable adaptability to cold and drought. As a pioneer species for ecological restoration and a high-quality forage grass, it holds significant ecological and economic value. However, the lack of a clear genetic background has hindered in-depth investigation of its adaptative mechanisms. Here, Oligo-FISH analysis revealed that Poa crymophila possesses 28 chromosomes in its somatic cells (2n=28). De-novo genome assembly yielded a 3.71 Gb autotetraploid genome (2n=4x=28, monoploid size ≈0.93 Gb) with 143,547 annotated protein-coding genes. Phylogenetic analysis indicated that P. crymophila diverged from Poa infirma and Poa supina 6.19–20.09 million years ago, coinciding with the rapid uplift event of the Qinghai-Tibetan Plateau, after which a whole-genome duplication drove its autotetraploidy. Comparative genomics revealed expansions in stress-tolerance gene families (e.g., cytochrome P450s, laccase LACs, Cold-Regulated CORs, etc.), and contractions in photosynthesis-related gene families. Additionally, 622 positively selected genes involved in metabolism, stress response and signaling were detected, including KMS1, which is shared with Tibetan Barley (Hordeum vulgare var. nudum) and Tibetan semi-wild wheat (Triticum aestivum subsp. tibeticum). Notably, P. crymophila could synthesize abundant schisandrin A under stress, a hepatoprotective secondary metabolite, further enhancing its value as a forage resource. These findings provide valuable genomic resources for breeding stress-tolerant forage crops and supporting ecological restoration in high-altitude regions.

Heterosis, characterized by enhanced performance of a hybrid relative to its parental lines, has been a fundament of plant breeding strategies. Despite the application of heterosis, its molecular mechanisms remain elusive. Here, we focused on the maize heterotic hybrid Yudan132, which showed enhanced agronomic traits compared to its parental lines, including ear and kernel size, kernel weight, and overall yield. Notably, Yudan132 showed increased accumulation of storage substances, characterized by starch, protein contents and grain-filling rates, all of which collectively contribute to the augmented kernel weight. Through gene expression profiling, we identified differentially expressed genes (DEGs) in Yudan132 and its parental lines across four distinct kernel developmental stages (12, 20, 28, and 40 days after pollination). These DEGs displayed both additive and non-additive expression patterns, each contributing to heterosis in maize kernels. The Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis highlighted their involvement in metabolic pathways, biosynthesis of secondary metabolites, carbon metabolism, starch and sucrose metabolism processes. Within these pathways, the enriched DEGs predominantly associated with the gene categories of peroxidase, cytochrome P450, ketoacyl-CoA synthase, and phospholipase D. Furthermore, we identified the transcription factor bZIP88 among the DEGs, which was involved in the regulation of seed size and weight in transgenic Arabidopsis. These results suggested a potential role for bZIP88 in modulating kernel development, thereby further implicating the involvement of the identified DEGs in the molecular mechanisms of heterosis. These findings provide the genetic role of heterosis in kernel and the molecular mechanism regulating kernel development.

Cultivated soybean (Glycine max), a significant oil and protein source, was domesticated from wild soybean (G. soja). Key traits of domestication syndrome underlying developmental evolution mechanisms remain poorly understood. In this study, cultivated soybean statistically flowered earlier than wild soybean, which correlated with 100-seed weight, implying that developmental heterochrony may be related to fruit/seed size variation during domestication. We compared fruit morphology and development and transcriptomic profiles in developing seeds between cultivar 'Suinong 14' (SN14) and wild soybean 'ZYD00006' (ZYD06), which exhibited similar flowering times. ZYD06 pods reached their ultimate size earlier than SN14, and the time to maximum fresh weight and seed maturation was longer in SN14 than in ZYD06. Cell division/expansion activities and the expression of related genes in developing pods/seeds were extended in SN14 relative to ZYD06. Differentially expressed genes (DEGs) related to cell division/expansion activities and oil/protein synthesis were enriched in developing seeds between SN14 and ZYD06. Integrated analyses of DEGs, gene co-expression networks, and quantitative trait loci revealed new candidate genes for soybean seed size variation. Transgenic Arabidopsis lines overexpressing Glyma.17G090200, which encoded a RING-finger E3 ubiquitin-protein ligase, showed an increased seed weight. Our findings suggest that heterochrony is a principal evolutionary developmental mechanism underlying soybean domestication, providing new insights and resources for soybean breeding and genetic improvement.

Macrolide pollution has attracted a great deal of attention because of its ecotoxic effects on microalgae, but the role of phycospheric bacteria under antibiotic stress remains unclear. This study explored the toxic effects of erythromycin (ERY) on the growth and nitrogen metabolism of Auxenochlorella pyrenoidosa; then, it analyzed and predicted the effects of the composition and ecological function of phycospheric bacteria on microalgae under ERY stress. We found that 0.1, 1.0, and 10 mg/L ERY inhibited the growth and chlorophyll of microalgae, but the microalgae gradually showed enhanced growth abilities over the course of 21 days. As the exposure time progressed, the nitrate reductase activities of the microalgae gradually increased, but remained significantly lower than that of the control group at 21 d. NO3− concentrations in all treatment groups decreased gradually and were consistent with microalgae growth. NO2− concentrations in the three treatment groups were lower than those in the control group during ERY exposure over 21 d. ERY changed the community composition and diversity of phycospheric bacteria. The relative abundance of bacteria, such as unclassified-f-Rhizobiaceae, Mesorhizobium, Sphingopyxis, Aquimonas, and Blastomonas, varied to different degrees. Metabolic functions, such ABC transporters, the microbial metabolism in diverse environments, and the biosynthesis of amino acids, were significantly upregulated in the treatments of higher concentrations (1.0 and 10 mg/L). Higher concentrations of ERY significantly inhibited nitrate denitrification, nitrous oxide denitrification, nitrite denitrification, and nitrite and nitrate respiration. The findings of this study suggest that phycospheric bacteria alleviate antibiotic stress and restore the growth of microalgae by regulating nitrogen metabolism in the exposure system.

Seed weight is a key component of crop yield. However, molecular mechanisms underlying soybean seed weight variation remain largely elusive. Here, we identify a major seed weight determining gene Glycine max SMALL SEED 6 (GmSMS6) that encodes a 14-3-3 protein. GmSMS6 physically and genetically interacts with the transcription factor GmbZIP151 and the RING-type E3 ligase GmUBQ1. GmSMS6 acts as a regulatory hub switch that coordinates the transcriptional activation activity and GmUBQ1-mediated stability of GmbZIP151, primarily repressing cellular expansion of soybean cotyledons. Knocking out GmSMS6 increases seed weight and protein content but decreases oil accumulation in multiple soybean genetic backgrounds. A loss-of-function allele of GmSMS6 is absent in available soybean resources, while the weakly expressed haplotype associated with heavy seed weight has undergone selection in G. max. These results provide insights into mechanisms underlying soybean domestication and highlight the importance of gene loss for improving crop yield and quality.

High temperatures significantly affect tea yield and quality. Arginine methylation is crucial for plant growth and environmental adaptation. However, its role in regulating plant responses to high temperatures remains unclear. In this study, we identified an important Type II arginine methyltransferase, PRMT5, in tea plants and confirmed its methyltransferase activity both in vivo and in vitro. Our findings revealed that CsPRMT5-mediated symmetric dimethylation of histone H4R3 (H4R3sme2) was markedly reduced under high-temperature conditions in tea plants. Both the inhibitor and gene-silencing approaches led to decreased levels of H4R3sme2 modification, resulting in alterations in theanine and catechins. We employed a genome-wide approach to analyze the RNA sequencing (RNA-seq) of tea plants subjected to ambient high temperatures, PRMT5 inhibitors, and PRMT5 silencing, along with H4R3sme2 and CsPRMT5 chromatin immunoprecipitation sequencing (ChIP-seq). Comparative analysis of these datasets indicated that genes regulated by H4R3sme2 were predominantly enriched within the reactive oxygen species (ROS), calcium ion, and hormone signalling pathways under elevated temperature conditions. Furthermore, we validated CsCDPK9 as a target gene regulated by H4R3sme2 and found that silencing CsCDPK9 resulted in increased theanine content and decreased catechin content at high temperatures. Our findings suggest that CsPRMT5-mediated H4R3sme2 plays a pivotal role in the growth of tea plants, as well as in their adaptability to fluctuations in ambient temperatures. This study provides new insights into breeding strategies aimed at developing crops that are better equipped to withstand environmental changes induced by climate change.

Severe high temperature (HT) climate significantly impacts cotton quality and yield. Consequently, it is essential to mine thermal-responsive genes and explore the underlying mechanisms of HT response in cotton. In this study, we employed a high-throughput cDNA-library method in conjunction with the ALRS system to screen thermotolerant genes in Upland cotton. As a result, a total of 16,120, 13,216 and 172 effective survival genes were filtered after HT stress exposure (42 °C, 220 rpm) for 48 h, 60 h and 72 h, respectively. Functional annotation and enrichment analysis revealed that 170 common genes were involved in regulatory processes associated with HT stress, and the relevant transcriptome data indicated that the majority of these genes responded to temperature fluctuations. Twenty-one genes were randomly selected for verification, and it was found that these genes could enhance yeast resistance to HT stress. Additionally, we selected mutants of homologous Arabidopsis genes for four candidate genes to validate plant thermotolerance during flowering; the thermotolerances of SALK_201915 and SALK_120540.1 were significantly worse. The results demonstrate that numerous candidate genes identified from the cDNA-library contribute to the highly complex molecular network that governs the response and resistance to HT stress in Upland cotton. The high-throughput heat-screening method utilized in this study was optimized for mining thermotolerant genes including improvement in yeast library construction, screening system, gradient reverse pressure, and sequencing library construction. We hope that this new method can be applied in future studies on stress in cotton and other species.

BACKGROUND: Rhizoctonia solani Kuhn is a pathogenic fungus causing tobacco target spot disease, and leads to great losses worldwide. At present, resistant varieties and effective control strategy on tobacco target spot disease are very limited. Host-induced gene silencing (HIGS) as well as the exogenous dsRNA can be used to suppress disease progression, and reveal the function of crucial genes involved in the growth and pathogenesis of the fungus. RESULTS: The silencing of endoPGs or RPMK1 in host plants by TRV-based HIGS resulted in a significant reduction in disease development in Nicotiana benthamiana. In vitro analysis validated that red fluorescence signals were consistently observed in the hyphae treated with Cy3-fluorescein-labeled dsRNA at 12, 24, 48 and 72 h postinoculation (hpi). Additionally, application of dsRNA-endoPGs, dsRNA-RPMK1 and dsRNA-PGMK (fusion of partial endoPGs and RPMK1 sequences) effectively inhibited the hyphal growth of R. solani YC-9 in vitro and suppressed disease progression in the leaves, and quantitative real-time PCR confirmed that the application of dsRNAs significantly reduced the expression levels of endoPGs and RPMK1. CONCLUSION: These results provide theoretical basis and new direction for RNAi approaches on the prevention and control of disease caused by R. solani. (c) 2024 Society of Chemical Industry. (c) 2024 Society of Chemical Industry.

Taxol is a widely-applied anticancer drug that inhibits microtubule dynamics in actively replicating cells. Although a minimum 19-step biosynthetic pathway has been proposed and 16 enzymes likely involved have been characterized, stepwise biosynthetic reactions from the well-characterized di-oxygenated taxoids to Taxol tetracyclic core skeleton are yet to be elucidated. Here, we uncover the biosynthetic pathways for a few tri-oxygenated taxoids via confirming the critical reaction order of the second and third hydroxylation steps, unearth a taxoid 9 α -hydroxylase catalyzing the fourth hydroxylation, and identify CYP725A55 catalyzing the oxetane ester formation via a cascade oxidation-concerted acyl rearrangement mechanism. After identifying a acetyltransferase catalyzing the formation of C7-OAc, the pathway producing the highly-oxygenated 1 β -dehydroxybaccatin VI with the Taxol tetracyclic core skeleton is elucidated and its complete biosynthesis from taxa-4(20),11(12)-diene-5 α -ol is achieved in an engineered yeast. These systematic studies lay the foundation for the complete elucidation of the biosynthetic pathway of Taxol.

Cyamopsis tetragonoloba (L.), an annual leguminous crop, with wide and important industrial applications. Its seeds contain large amounts of guar gum, main ingredient is galactomannan, have multiple application values. To reveal the genome resource of guar, this study describes the assembly of C. tetragonoloba chromosome-level genome CteV1.0. There were 18.35 Gb high accuracy HiFi data with the more than 40x sequencing depth were generated by the PacBio platform with average length 22.61 kb. Finally, the assembled size of C. tetragonoloba genome was 482.45 Mb with a 62.64 Mb scaffold N50. Then with Hi-C assembly and adjustment, the 99.07% (477.96 Mb/482.45 Mb) of genome data was assigned to 7 pseudochromosomes. A total of 31,251 genes (31251/31867, 98.07%) were successfully annotated, and 309 gene families contracted, 559 gene families expanded in C. tetragonoloba. This genome of guar provides fundamental biological information of the industrial benefits, biophysiological functions and unique evolutionary relationship. The comparison between guar and other related short-day and long-day species characterized the photoperiodic differences in genomic scale. The construction of genome assembly, gene function and photoperiod adaption in C. tetragonoloba may reveal the basic theoretical fundament of the special traits in C. tetragonoloba. This available high-quality genomic resource in this study will facilitate future research in guar field.

As a primary approach to nutrient propagation for many woody plants, cutting roots is essential for the breeding and production of Eucommia ulmoides Oliver. In this study, hormone level, transcriptomics, and metabolomics analyses were performed on two E. ulmoides varieties with different adventitious root (AR) formation abilities. The higher JA level on the 0th day and the lower JA level on the 18th day promoted superior AR development. Several hub genes executed crucial roles in the crosstalk regulation of JA and other hormones, including F-box protein (EU012075), SAUR-like protein (EU0125382), LOB protein (EU0124232), AP2/ERF transcription factor (EU0128499), and CYP450 protein (EU0127354). Differentially expressed genes (DEGs) and metabolites of AR formation were enriched in phenylpropanoid biosynthesis, flavonoid biosynthesis, and isoflavonoid biosynthesis pathways. The up-regulated expression of PAL, CCR, CAD, DFR, and HIDH genes on the 18th day could contribute to AR formation. The 130 cis-acting lncRNAs had potential regulatory functions on hub genes in the module that significantly correlated with JA and DEGs in three metabolism pathways. These revealed key molecules, and vital pathways provided more comprehensive insight for the AR formation mechanism of E. ulmoides and other plants.

ABSTRACTThe 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 inArabidopsisplay 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 areO-fucosylated in their middle region (MR) by SPINDLY (SPY), a novel nucleocytoplasmic proteinO-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 alsoO-fucosylated by SPY. Biochemical assays demonstrated that SPY-mediatedO-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 proteinO-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.