Genome sequences provide fundamental information for both basic and applied life sciences. Whole-genome sequencing is now requested for describing novel prokaryotic species and designating their type strains, which serve as representative and well-characterized strains of the species. Indeed, the number of sequenced prokaryotic genomes has been rapidly increasing. However, a considerable number of isolated strains, particularly technically demanding strains such as strict anaerobes and slow growers, remain without genome sequence information. Here we report the whole-genome sequencing of 290 bacterial and 61 archaeal strains, including technically demanding type strains, obtained from the Japan Collection of Microorganisms (JCM) using a combination of short- and long-read sequencing technologies. The data set includes 284 type-strain genomes and 235 complete genomes. Notably, in the data set, genomes of more than 200 strains, including more than 150 type strains, have not been made publicly available. Comparative genomic analysis suggests that some strains need to be assigned to novel taxa or reclassified. Functional gene survey indicates that some strains possess previously unrecognized potential for carbon fixation or bioactive secondary metabolite production. Our data set will contribute to more accurate taxonomic classification, fill gaps in the phylogeny of prokaryotes, and provide insights into their physiology and ecology.

Bradyrhizobium, the largest rhizobial genus, is characterized by a variety of exopolysaccharide (EPS) components, such as penta- and tetrasaccharides, depending on the species. However, several genes involved in EPS synthesis remain unknown. In this study, we investigated whether 186 Bradyrhizobium strains possess homologous genes in the EPS cluster I, which is responsible for the synthesis of a pentasaccharide EPS by B. diazoefficiens USDA110. The absence of homologous genes in the B. elkanii and Photosynthetic Bradyrhizobium supergroups, in contrast to the B. japonicum supergroup, suggests that these lineages may utilize distinct and uncharacterized genes involved in tetrasaccharide EPS biosynthesis.

Plant roots are hotspots for interactions with soil microbes, where a characteristic bacterial community structure is formed. Plant specialized metabolites often play pivotal roles in this assembly process. However, the molecular basis underlying root microbiota responses to these bioactive compounds, and how such metabolic interactions shape the assembly of host-specific root microbiota, remain largely unknown. Nicotine is a toxic alkaloid predominantly produced by the genus Nicotiana, and the genus Arthrobacter is known as one of the nicotine-degrading bacteria in the tobacco root microbiota. In this study, we used the tobacco–Arthrobacter interaction system as a model and integrated comparative genomics and experimental genetic manipulation assays to uncover the role of bacterial catabolism capacity for host specialized metabolites in shaping host-specific root microbiota. Nicotine catabolism genes are uniquely found in the Arthrobacter strains derived from nicotine-containing environments, and this restricted gene distribution is driven by a plasmid-mediated horizontal gene transfer. To assess the ecological consequences of this genomic adaptation in Arthrobacter fitness in tobacco roots, we characterized the nicotine utilization ability of Arthrobacter and conducted adaptation assays under in planta conditions using genetically manipulated Arthrobacter strains and tobacco mutants impaired in nicotine catabolism and biosynthesis, respectively. Nicotine improves Arthrobacter colonization of tobacco roots through a catabolism-dependent mechanism. Bacterial community analysis using a synthetic community approach further demonstrated that this metabolic adaptation enhances Arthrobacter fitness within tobacco root microbiota. Our findings illustrated that bacterial catabolic capacity toward host-derived plant specialized metabolites is key for successful root colonization. This metabolic adaptation is driven by plasmid-mediated horizontal gene transfer and ultimately shapes the structure of the root microbiota community.

Defined microbial communities (DMCs; also known as SynComs) offer a promising strategy to enhance plant growth and stress tolerance by harnessing beneficial plant-associated microbes. However, the rational design and efficient exploration of complex DMC configurations remain challenging. Here, we present an interpretable model-guided framework that integrates plant phenotyping, microbial genomics, and machine learning to optimize DMC outcomes and identify microbial interactions relevant to plant performance. Using tomato as a model, we evaluated diverse DMC, temperature, and metabolite combinations in growth experiment and used a quality-controlled dataset comprising 301 plants representing 102 DMC compositions for predictive modeling. An Elastic Net regression model trained on plant biomass data and DMC composition features enabled prediction of unseen DMC outcomes, and incorporating genomic features substantially improved predictive performance, supporting the importance of functional potential in modeling community effects. We applied the model to prioritize and design improved DMCs, which were validated in laboratory assays and field trials. One model-guided DMC significantly enhanced plant growth in the field and improved heat stress tolerance under controlled conditions. Model interpretation and multi-omics analyses highlighted specific microbial interactions, including metabolite-associated relationships involving Sphingobium sp. and tomatine, that were linked to host stress-responsive gene expression. Together, our results demonstrate a scalable framework for predicting and prioritizing DMCs and identify candidate metabolite-associated microbial interactions that may contribute to plant growth promotion and abiotic stress tolerance.

Synthetic microbial communities (SynComs) represent a promising approach to enhance crop growth and stress resilience through microbiome engineering. However, the systematic design and field validation of SynComs remain limited. Here, we present a predictive framework for SynCom optimization, integrating plant phenotyping, microbial genomics, and machine learning. Using tomato as a model, we tested over 800 SynCom–temperature combinations consisting of root endophytic bacteria and rhizosphere metabolites. An Elastic Net regression model trained on plant biomass data accurately predicted the performance of unseen SynComs, with prediction accuracy plateauing at ∼5% (301/6144) of all possible SynCom–temperature combinations. Incorporating genomic features significantly improved model performance, whereas microbiome compositional data alone were not informative. We applied the model to design novel SynComs, which were tested in both laboratory and field conditions using a commercial tomato cultivar. The model-informed SynCom enhanced plant growth in field trials and improved heat stress tolerance under controlled laboratory conditions. Multi-omics analyses and feature importance metrics identified specific microbial taxa, including Sphingobium sp., whose enrichment was linked to host plant metabolite (e.g., tomatine) and stress-responsive gene expression. Our results demonstrate a scalable strategy for the predictive design of beneficial microbiomes to improve resilient crop performance under real-world conditions. ### Competing Interest Statement The authors have declared no competing interest. Japan Science and Technology Agency CREST, JPMJCR15O2, JPMJCR17O2 GteX Program Japan, JPMJGX23B2 RIKEN TRIP Initiative

Soybeans fix atmospheric N2 through symbiosis with rhizobia. The relationship between rhizobia and soybeans, particularly those with high nitrous oxide (N2O)-reducing (N2OR) activities, can be leveraged to reduce N2O emissions from agricultural soils. However, inoculating soybeans with these rhizobia under field conditions often fails because of the competition from indigenous rhizobia that possess low or no N2OR activity. In this work, we utilize natural incompatibility systems between soybean and rhizobia to address this challenge. Specifically, Rj2 and GmNNL1 inhibit certain rhizobial infections in response to NopP, an effector protein. By combining a soybean line with a hybrid accumulation of the Rj2 and GmNNL1 genes and bradyrhizobia lacking the nopP gene, we develop a soybean-bradyrhizobial symbiosis system in which strains with high N2OR activity predominantly infect. Our optimize symbiotic system substantially reduces N2O emissions in field and laboratory tests, presenting a promising approach for sustainable agricultural practices.

Background: Plant roots are hotspots for interactions with soil microbes, where a characteristic bacterial community structure is formed. Plant specialized metabolites often play pivotal roles in this assembly process. However, the molecular basis underlying root microbiota responses to these bioactive compounds, and how such metabolic interactions shape the assembly of host-specific root microbiota, remain largely unknown. Nicotine is a toxic alkaloid predominantly produced by the genus Nicotiana, and the genus Arthrobacter is known as one of the nicotine-degrading bacteria in the tobacco root microbiota. In this study, we used the tobacco-Arthrobacter interaction system as a model and integrated comparative genomics and experimental genetic manipulation assays to uncover the role of bacterial catabolism capacity for host specialized metabolites in shaping host-specific root microbiota. Results: Nicotine catabolism genes are uniquely found in the Arthrobacter strains derived from nicotine-containing environments, and this restricted gene distribution is driven by a plasmid-mediated horizontal gene transfer. To assess the ecological consequences of this genomic adaptation in Arthrobacter fitness in tobacco roots, we conducted adaptation assays under both in vitro and in planta conditions using genetically manipulated Arthrobacter and tobacco mutants, which are impaired in nicotine catabolism and biosynthesis, respectively. Nicotine improves Arthrobacter colonization to the tobacco roots through both catabolism-dependent and catabolism-independent mechanisms. Bacterial community analysis using a synthetic community approach further demonstrated that these metabolic interactions, mediated by tobacco nicotine biosynthesis and its catabolism by Arthrobacter, jointly affect root microbiota composition. Conclusions: Our findings illustrated that bacterial catabolic capacity toward host-derived plant specialized metabolites is key for successful root colonization. This metabolic adaptation is driven by plasmid-mediated horizontal gene transfer and ultimately shapes the structure of the overall root microbiota community. ### Competing Interest Statement The authors have declared no competing interest. Japan Society for the Promotion of Science, Research Fellowship for Young Scientists PD, 22KJ3147 Japan Society for the Promotion of Science, KAKENHI grants, 22K21367 Mayekawa Houonkai Foundation, https://ror.org/05qkcsb49 Humanosphere Science Research of RISH RIKEN TRIP initiative

Parasitic plants will initiate rapid de novo organogenesis of a specialized feeding structure called a haustorium upon contact with their hosts. Currently, little is known about the internal signals regulating haustorium development. Here, we identify root meristem growth factor (RGF) peptides in Phtheirospermum japonicum as endogenous inducers of prehaustorium formation. Treatment with specific RGF peptides in the absence of hosts triggered prehaustoria and induced expression of PjYUC3, a gene required for auxin biosynthesis and prehaustorium formation. CRISPR-mediated knockouts showed that PjRGFR1 and PjRGFR3, receptors activated by the haustorium-specific RGF peptides PjRGF2 and PjRGF5, are essential for prehaustorium formation, revealing functional redundancy. Phylogenetic analyses indicate that PjRGF2 is broadly conserved among Orobanchaceae, whereas PjRGF5 appears to have recently evolved through segmental tandem multiplication. Our findings establish RGF peptides and their corresponding receptors as critical components of haustorium developmental signaling and provide insights into the evolutionary trajectories that shape plant parasitism.

The phyllosphere is a major microbial habitat, where resident communities promote plant growth, suppress pathogens, and induce disease resistance. Here we examined how rice growth stages influence microbial colonization by analyzing bacterial communities in the phyllospheres of three growth stages (panicle initiation, heading, harvesting) across three genotypes: 'Koshihikari' and two introgression lines. Bacterial communities were similar among genotypes in both leaves and stems at heading but became distinct at harvesting, indicating that growth stages and plant organ play primary roles in shaping community structure. Full-length 16S rRNA gene amplicon sequencing further revealed significant shifts in species composition, with Pseudomonas species, such as Pseudomonas brenneri and Pseudomonas helmanticensis, were consistently present across organs and stages, while Enterobacter species showed stage-specific colonization. These findings highlight the dynamic nature of phyllosphere microbial communities throughout plant development and underscore the importance of organ- and stage-specific factors in shaping plant-microbe interactions.

Symbiosis between Bradyrhizobium strains isolated from Lao People's Democratic Republic (Lao PDR) and intercropped legumes (Arachis hypogaea, Vigna radiata, and V. mungo) was regulated by the type III secretion system (T3SS), which delivers effector proteins (T3Es) into host plant cells to modulate nodulation. To explore this mechanism, we sequenced and analyzed seven Bradyrhizobium genomes, identifying putative T3Es across five T3SS groups (G.1-G.5), which were classified based on the sequence of rhcN, a conserved ATPase gene essential for T3SS function. Phylogenetic analysis of rhcN more closely reflected the evolutionary relationships of nodulation genes than those based on 16S rRNA or whole-genome comparisons, underscoring its symbiotic relevance. Functional assays using rhcN mutants revealed group-specific effects on nodulation; G.1 strains showed neutral effects on A. hypogaea, negative effects on V. radiata, and positive effects on V. mungo. G.2 strains consistently promoted nodulation across all hosts and lacked effectors related to SUMO (small ubiquitin-like modifier) pathways, which have been implicated in host defense regulation. G.3 strains reduced nodulation in A. hypogaea but enhanced it in Vigna species. G.4 strains suppressed nodulation in A. hypogaea, and G.5 strains inhibited nodulation across all tested legumes. These findings highlight the diversity in T3SS organization, effector composition, and symbiotic responses among native Bradyrhizobium strains. The identification of known and uncharacterized effectors suggests roles in host compatibility and specificity. These strains, along with their effector profiles, provide a foundation for future functional studies to better understand T3SS-mediated interactions and support the development of targeted inoculants for legume hosts.IMPORTANCEThis study advances our understanding of legume-Bradyrhizobium symbiosis by examining the genetic organization and evolutionary patterns of T3SS genes. Our findings revealed that T3SS gene evolution does not always align with phylogenies based on 16S rRNA or whole-genome sequences, suggesting that horizontal gene transfer and functional adaptation may shape diversification. The observed variation in T3SS architecture and effector profiles among the five distinct Bradyrhizobium groups was correlated with host-specific nodulation outcomes in A. hypogaea, V. radiata, and V. mungo. We also identified novel candidate genes influencing symbiotic signaling and compatibility. These insights into the diversity and function of T3SS components contribute to a broader understanding of host-microbe communication and may support the development of more targeted and efficient rhizobial inoculants for sustainable legume cultivation and improved biological nitrogen fixation.

Centromeres are essential for chromosome function, yet their role in shaping genome evolution in polyploid plants remains poorly understood. Allopolyploidy, where post-hybridization genome doubling merges parental genomes that may differ markedly in chromosomal architecture, has the potential to increase centromeric complexity and influence genomic plasticity. We explore this possibility in carnivorous Caryophyllales, a morphologically and chromosomally diverse plant lineage encompassing sundews, Venus flytraps, and Nepenthes pitcher plants. Focusing on sundews ( Drosera ), we generated chromosome-scale assemblies of holocentric D. regia and monocentric D. capensis , which share an allohexaploid origin but have diverged dramatically in genome structure. D. regia retains ancestral chromosomal fusions, dispersed centromeric repeats, and conserved synteny, whereas D. capensis exhibits extensive chromosomal reorganization and regionally localized centromeres after a lineage-specific genome duplication. Phylogenomic evidence traces D. regia to an ancient hybridization between sundew- and Venus flytrap-like ancestors, setting it apart within its infrageneric context. Genus-wide satellite DNA repeat profiling reveals rapid turnover and species-level variation in centromere organization. Together, these results establish sundews as a natural system for investigating how centromere dynamics interact with recurrent polyploidization and episodes of ecological innovation to shape genomic resilience. ### Competing Interest Statement The authors have declared no competing interest.

Flooded rice fields are a major source of atmospheric methane, a strong greenhouse gas second only to carbon dioxide. Rice roots are one of the most important hotspots for methane oxidation in rice fields. However, limited information is available on the physiological and genomic characteristics of methane-oxidizing bacteria (MOB) inhabiting rice roots. In the present study, we isolated MOB from rice roots and characterized the strains phenotypically and genomically. We obtained 100 MOB-enriched cultures from the roots of three rice cultivars (Oryza sativa L. subsp. japonica cv. Nipponbare, O. sativa L. subsp. indica cv. Muha, and Tupa 121-3), in which twelve MOB isolates, two Methylomonas sp., three Methylocystis sp., and seven Methylosinus sp., were successfully purified. They showed different morphological features (types of flagellation) and colony formation potentials within the same group in some cases. A genome sequencing ana-lysis revealed variations in the number of genes or the clusters of methane monooxygenase, methanol dehydrogenase, and nitrogenase. The number of plasmid DNAs also differed among the strains. Four strains belonging to the genus Methylomonas or Methylocystis represented putative novel species based on their phenotypic and genotypic characteristics. The present study largely expanded the eco-collection of MOB cultures inhabiting rice fields and rice roots.

Since nitrogenase is intrinsically sensitive to oxygen (O2), diverse aerobic diazotrophs need strategies to cope with nitrogenase damage by O2. In the present study, we investigated the mechanisms by which aerobic methane-oxidizing bacteria (methanotrophs) enable the concurrent activities of methane monooxygenase, which uses O2, and nitrogenase in the cytoplasm of the same cell. By using 15N labeling, we confirmed the capacity of alphaproteobacterial methanotroph Methylosinus sp. 3S-1 for nitrogen fixation and diazotrophic growth across a wide range of O2 concentrations <20%. When the initial O2 concentration was increased from 2 to 20% in a diazotrophic culture, similar decreases were observed in fixed nitrogen and NifH protein levels. In contrast, the mRNA levels of nitrogen fixation genes (nif genes) markedly increased and remained elevated for the duration of slow growth at high O2 concentrations. This pattern of nif expression in response to O2 may be attributed to the properties of the nif-specific transcriptional regulator NifA. The present results suggest that the increase in nif transcription is one of the strategies by which this methanotroph maintains nitrogen fixation on the background of aerobic methane oxidation.

Hairy root transformation mediated by Rhizobium rhizogenes is a widely used tool for molecular analysis and root material for secondary metabolite production. However, this method is time-intensive, technically demanding, and exhibits low transformation efficiency. To address these limitations, we developed a rapid and efficient hairy root transformation system for legume crops, optimizing protocols with the soybean (Glycine max L. Merrill) cultivar Fukuyutaka. Sterilizing seeds with vapor of 5% sodium hypochlorite and germinating them in a double-tier container resulted in over 90% healthy, straight seedlings ideal for transformation, with 3- to 5-day-old seedlings showing the highest transformation rates. Exposing the plant shoot during co-cultivation by covering only the injection area, combined with low nitrogen levels in the hydroponic solution, significantly enhanced hairy root production, yielding up to 16 transgenic hairy roots per plant. Additionally, low nitrogen concentrations were crucial for promoting nodule formation in transgenic hairy roots. These optimized conditions were validated across 12 soybean, 1 cowpea, and 1 mungbean cultivars. The protocol's effectiveness was confirmed through the induction of symbiotic gene expression of GmEnod40a and GmErn1b using a promoter β-glucuronidase (GUS) reporter system in transgenic hairy roots. Expression of these genes was detected in both premature and mature nodules, while GmErn1b expression was also observed in epidermal cells during early nodulation. This optimized hairy root transformation protocol, requiring under 22 days from seed sterilization to transgenic root induction and 61 days to expression analysis, offers a promising approach for efficient gene function studies in legume crops.

Pseudomonas syringae pv. tabaci (Pta) is an important plant pathogen, which causes wildfire disease in Nicotiana species. However, the genetic basis underlying strain-level differences in virulence remains largely unresolved. To address this, we performed a comparative genomic analysis between a highly virulent strain Pta6605 and a less virulent strain Pta7375. Despite high overall genome similarity, we identified key single-nucleotide polymorphisms, including premature stop-codon mutations in seven open reading frames in Pta7375. Notably, point mutations in two regulatory genes, such as fleQ, which encodes a transcription factor essential for flagellar biogenesis and biofilm formation, and gcbB, which encodes a GGDEF domain-containing diguanylate cyclase responsible for cyclic dimeric guanosine monophosphate (c-di-GMP) synthesis, were implicated in virulence disparity. Functional analyses using deletion and locus replacement mutants in the Pta6605 background revealed that the disruption of fleQ markedly reduced motility, flagellin production, c-di-GMP accumulation, biofilm formation and virulence level mirroring the Pta7375 phenotype. The gcbB replacement mutant showed reduced disease symptom development, although c-di-GMP levels remained comparable to the Pta6605 wild type. Locus replacement between strains confirmed that a point mutation in fleQ was the primary driver of reduced motility and flagellin expression in Pta7375. These findings indicate that the reduced virulence of Pta7375 is associated with impaired regulation of flagella-related genes and disruption of the FleQ-mediated c-di-GMP signalling, underscoring the value of comparative genomics in disentangling the complex regulatory networks that govern virulence in plant pathogens.

Although microbial inoculation may be effective for sustainable crop production, detrimental aspects have been argued because of the potential of inoculated microorganisms to behave as invaders and negatively affect the microbial ecosystem. We herein compared the impact of rhizobial inoculation on the soil bacterial community with that of agricultural land-use changes using a 16S rRNA amplicon ana-lysis. Soybean plants were cultivated with and without five types of bradyrhizobial inoculants (Bradyrhizobium diazoefficiens or Bradyrhizobium ottawaense) in experimental fields of Andosol, and the high nodule occupancy (35-72%) of bradyrhizobial inoculants was confirmed by nosZ PCR. However, bradyrhizobial inoculants did not significantly affect Shannon's diversity index (α-diversity) or shifts (β-diversity) in the bacterial community in the soils. Moreover, the soil bacterial community was significantly affected by land-use types (conventional cropping, organic cropping, and original forest), where β-diversity correlated with soil chemical properties (pH, carbon, and nitrogen contents). Therefore, the effects of bradyrhizobial inoculation on bacterial communities in bulk soil were minor, regardless of high nodule occupancy. We also observed a correlation between the relative abundance of bacterial classes (Alphaproteobacteria, Gammaproteobacteria, and Gemmatimonadetes) and land-use types or soil chemical properties. The impact of microbial inoculation on soil microbial ecosystems has been exami-ned to a limited extent, such as rhizosphere communities and viability. In the present study, we found that bacterial community shifts in soil were more strongly affected by land usage than by rhizobial inoculation. Therefore, the results obtained herein highlight the importance of assessing microbial inoculants in consideration of the entire land management system.

Plant roots secrete various metabolites, including plant specialized metabolites, into the rhizosphere, and shape the rhizosphere microbiome, which is crucial for the plant health and growth. Isoflavones are major plant specialized metabolites found in legume plants, and are involved in interactions with soil microorganisms as initiation signals in rhizobial symbiosis and as modulators of the legume root microbiota. However, it remains largely unknown the molecular basis underlying the isoflavone-mediated interkingdom interactions in the legume rhizosphere. Here, we isolated Variovorax sp. strain V35, a member of the Comamonadaceae that harbors isoflavone-degrading activity, from soybean roots and discovered a gene cluster responsible for isoflavone degradation named ifc. The characterization of ifc mutants and heterologously expressed Ifc enzymes revealed that isoflavones undergo oxidative catabolism, which is different from the reductive metabolic pathways observed in gut microbiota. We further demonstrated that the ifc genes are frequently found in bacterial strains isolated from legume plants, including mutualistic rhizobia, and contribute to the detoxification of the antibacterial activity of isoflavones. Taken together, our findings reveal an isoflavone catabolism gene cluster in the soybean root microbiota, providing molecular insights into isoflavone-mediated legume-microbiota interactions.

The plant microbiome is crucial for plant growth, yet many important questions remain, such as the identification of specific bacterial species in plants, their genetic content, and location of these genes on chromosomes or plasmids. To gain insights into the genetic makeup of the rice-phyllosphere, we perform a metagenomic analysis using long-read sequences. Here, 1.8 Gb reads are assembled into 26,067 contigs including 142 circular sequences. Within these contigs, 669 complete 16S rRNA genes are clustered into 166 bacterial species, 121 of which show low identity (<97%) to defined sequences, suggesting novel species. The circular contigs contain novel chromosomes and a megaplasmid, and most of the smaller circular contigs are defined as novel plasmids or bacteriophages. One circular contig represents the complete chromosome of a difficult-to-culture bacterium Candidatus Saccharibacteria . Our findings demonstrate the efficacy of long-read-based metagenomics for profiling microbial communities and discovering novel sequences in plant-microbiome studies.

Actinomycetes are prolific producers of natural products, particularly antibiotics. However, a significant proportion of its biosynthetic gene clusters (BGCs) remain silent under typical laboratory conditions. This limits the effectiveness of conventional isolation methods for the discovery of novel natural products. Genetic interventions targeting the activation of silent gene clusters are necessary to address this challenge. Streptomyces antibiotic regulatory proteins (SARPs) act as cluster-specific activators and can be used to target silent BGCs for the discovery of new antibiotics. In this study, the expression of a previously uncharacterized SARP protein, Syo_1.56, in Streptomyces sp. RK18-A0406 significantly enhanced the production of known antimycins and led to the discovery of 12 elasnins (1-12), 10 of which were novel. The absolute stereochemistry of elasnin A1 was assigned for the first time to be 6S. Unexpectedly, Syo_1.56 seems to function as a pleiotropic rather than cluster-specific SARP regulator, with the capability of co-regulating two distinct biosynthetic pathways, simultaneously. All isolated elasnins were active against wild-type and methicillin-resistant Staphylococcus aureus with IC50 values of 0.5-20 μg/mL, some of which (elasnins A1, B2, and C1 and proelasnins A1, and C1) demonstrated moderate to strong antimalarial activities against Plasmodium falciparum 3D7. Elasnins A1, B3, and C1 also showed in vitro inhibition of the metallo-β-lactamase responsible for the development of highly antibiotic-resistant bacterial strains.

Hibiscus trionum, commonly known as the 'Flower of an Hour', is an easily cultivated plant in the Malvaceae family that is widespread in tropical and temperate regions, including drylands. The purple base part of its petal exhibits structural colour due to the fine ridges on the epidermal cell surface, and the molecular mechanism of ridge formation has been actively investigated. We performed genome sequencing of H. trionum using a long-read sequencing technology with transcriptome and pathway analyses to identify candidate genes for fine structure formation. The ortholog of AtSHINE1, which is involved in the biosynthesis of cuticular wax in Arabidopsis thaliana, was significantly overexpressed in the iridescent tissue. In addition, orthologs of AtCUS2 and AtCYP77A, which contribute to cutin synthesis, were also overexpressed. Our results provide important insights into the formation of fine ridges on epidermal cells in plants using H. trionum as a model.