Biology subjects

Shirasawa, K.

Publications and source records attributed to Shirasawa, K..

At least 19 recordsLinked to original sources

bioRxiv2026

A naturally occurring frameshift mutation in the UNUSUAL FLORAL ORGANS gene associated with the marimo floral phenotype in gerbera

BackgroundThe capitulum of Asteraceae is a highly specialized inflorescence whose formation requires the coordinated regulation of multiple developmental processes, including floral organ identity and floral meristem determinacy. The LEAFY (LFY)-UNUSUAL FLORAL ORGANS (UFO) regulatory module is known to play an important role in flower development; however, naturally occurring mutations affecting this pathway have not been genetically characterized in gerbera (Gerbera hybrida). ResultsIn this study, we characterized a novel gerbera mutant identified during a commercial crossing program and named it marimo based on its green, spherical capitulum. Morphological observations revealed the repeated formation of secondary and tertiary floret-like organs within primary floret-like organs. Scanning electron microscopy showed that the epidermal structure of the green organs in marimo was similar to that of wild-type involucral bracts. RNA sequencing identified numerous differentially expressed genes between marimo and the wild type, and network and Gene Ontology analyses highlighted gene groups associated with flower development, reproductive organ differentiation, and tissue structure formation. RNA-seq analysis showed increased expression of LFY and reduced expression of GGLO1, a PISTILLATA/GLOBOSA-like B-class MADS-box gene, in the marimo mutant. RT-qPCR analysis of a segregating population further confirmed reduced GGLO1 expression in marimo-type individuals. In addition, a single-nucleotide deletion was identified in the coding region of UFO. This deletion was predicted to cause a frameshift and a premature stop codon. In selfed progeny of No. 251, the UFO genotype was fully associated with capitulum phenotype, and only individuals homozygous for the mutant allele exhibited the marimo phenotype. ConclusionsThese results indicate that the naturally occurring frameshift mutation in UFO is the strongest candidate variant underlying the marimo phenotype. RNA-seq analysis showed increased LFY expression and markedly reduced GGLO1 expression in the marimo mutant. Reduced activity of the LFY-UFO regulatory module may therefore have altered the expression of GGLO1 and other floral organ development-related genes despite the continued expression of LFY. These changes may have affected both floral organ identity and floral meristem determinacy, resulting in the formation of green involucral bract-like organs and the repeated production of floret-like organs. The marimo mutant provides a useful genetic resource for investigating capitulum development in Asteraceae and may also serve as breeding material for introducing novel ornamental traits into gerbera.

genetics↗

bioRxiv2026

Independent evolution of flavour and parthenocarpy in fig, one of the earliest domesticated fruit trees

Domestication often modifies multiple traits in concert, but whether fruit quality and reproductive mode share a genetic basis in perennial crops has not been tested at multi-omics resolution. In fig (Ficus carica), one of the earliest domesticated fruit trees and a crop with archaeobotanical evidence of cultivation over 11,000 years ago, domestication yielded both distinctive flavour and parthenocarpy, fruit development without pollination. We integrated whole-genome resequencing, transcriptomics, volatile and metabolite profiling, and taste sensor data across a diverse accession panel, using Bayesian GWAS/TWAS and multi-omics factor analysis. Flavour emerges as an integrated sensory system led by aroma, which modulates taste through cross-modal interactions, with sugar-acid balance as a secondary axis; these quality traits map to numerous independent loci. Parthenocarpy instead traces to a single perfectly concordant chromosome 04 haplotype (Eden) centred on FcMYB101-like, carrying a selective-sweep signature and a derived allele fixed in cultivated figs but rare across the genus. Flavour and reproductive mode thus evolved along separate genomic trajectories, allowing each to be improved independently.

plant biology↗

bioRxiv2026

A highly contiguous genome assembly of Cyclamen persicum to accelerate functional genomics and breeding

Cyclamen is an economically important ornamental plant widely cultivated for its diverse floral characteristics and adaptation to cool climates. Despite its horticultural significance, genomic resources for this species remain limited, hindering molecular studies and genomics-assisted breeding. Here, we report the first highly contiguous nuclear genome assembly of C. persicum generated using high-fidelity long-read sequencing. The assembled genome spans 1.48 Gb, consisting of 126 contigs with an N50 length of 52.3 Mb. Telomeric repeat analysis identified eight contigs containing telomeric sequences at both ends, suggesting the presence of near-complete chromosome assemblies. Genome completeness assessment using BUSCO indicated 98.1% completeness. Repetitive sequences occupied 82.9% of the assembly, with long terminal repeat retrotransposons accounting for 42.1% of the genome. A total of 40,223 protein-coding genes were predicted, with a complete BUSCO score of 95.7%. Comparative orthogroup analysis with five representative eudicot species identified 430 orthogroups specific to C. persicum and 363 orthogroups shared exclusively between C. persicum and Primula kwangtungensis, indicating the presence of both lineage-specific and Primulaceae-conserved gene families. These findings provide critical insights into gene family evolution within Primulaceae and establish an essential comparative framework for future genomic studies. The genome resource presented here provides an invaluable foundation for investigating genome evolution, gene function, and trait-associated loci in cyclamen, effectively facilitating molecular breeding and genetic improvement in this ornamental species.

genomics↗

bioRxiv2026

Chromosome-scale genome assembly of Cycas revoluta provides insights into cycad diversification and species diversity

Cycads are an ancient group of seed plants. Despite their ancient origin, many extant cycad genera exhibit high species diversity. The specialized reproductive traits in cycads, dioecy governed by the XY sex-determination system and the elaborate co-evolutionary synergy with insect pollinators, may facilitate lineage diversification. Here, we present a chromosome-scale genome sequence of Cycas revoluta, the species in which plant spermatozoids were discovered in 1896. The genome sequence spanned 11.6 Gb, 98.4% of which were anchored onto the 11 cycad chromosomes. Repetitive sequences occupied 9.8 Gb, and 31,481 genes were predicted. Based on this genome assembly, the X- and Y-associated genomic regions were characterized, and candidate genes for sex determination were identified. In addition, the genomic positions of genes for sex-related traits were determined. Subsequently, we analyzed transcriptomes for thermogenesis responsible for attracting insect pollinators. Through these comprehensive analyses, we provide new insights into the genomic basis of cycad diversification and species diversity.

genomics↗

bioRxiv2026

Genomic basis of rapid urban evolution revealed by the subgenome-resolved genome of octoploid Oxalis corniculata

Urbanization is a major driver of contemporary evolution, yet the genomic basis of urban adaptation remains poorly understood, particularly in non-model plants with complex polyploid genomes. Here, we investigate the genetic mechanisms underlying leaf color variation in the octoploid Oxalis corniculata, a phenotype associated with heat tolerance in urban environments. By integrating high-fidelity long-read sequencing and chromosome conformation capture, we generated the subgenome-resolved, chromosome-scale genome assemblies for both red- and green-leaved lines, resolving four distinct subgenomes. LTR insertion timing revealed a two-step hybridization history that established this octoploid genome within the last 1 million years. Leveraging a nationwide citizen science initiative, we collected and analyzed over 1,700 samples across a broad geographic range. We identified a major locus on one subgenome underlying this variation and implicate a coding-sequence repeat-length polymorphism in a MYB transcription factor as the candidate causal variant. This simple sequence repeat likely acts as a molecular "tuning knob" for rapid adaptation to urban heat islands. This study provides a new baseline for evolutionary ecological genomics in plants and highlights the power of integrating advanced genomics with public participation to forecast evolutionary responses in an increasingly urbanized world.

genomics↗

bioRxiv2026

A pistil peptide toxin-pollen antidote system for reproductive barrier

Summary paragraphPrezygotic reproductive barriers in angiosperms are crucial for female-mediated selection of compatible male gametes. In this study, we identified a biological activity within the stylar tissues of Arabidopsis thaliana pistils that inhibits the elongation of heterospecific pollen tubes. Using genome-wide association studies, we identified a cysteine-rich peptide predominantly expressed in the style as the responsible barrier. This secreted peptide, named Femme fatale (FEM), inhibited pollen tube elongation of heterospecific species and some conspecific strains, both in vivo and in vitro. Importantly, FEMs function was independent of the known reproductive barrier component SPRI1 that functions in the stigmatic papilla cell surface. This means two factors act spatially in sequence to create a multilayered reproductive barrier system against pollen in pistils. We also identified a secreted protein expressed in pollen, Homme capable (HOM), which is encoded by a gene next to FEM. HOM interacts with FEM to counteract its barrier effect and allow pollen tube elongation. The FEM-HOM locus has undergone frequent tandem duplications during Brassicaceae evolution. Dosage differences between the two factors can lead to reproductive incompatibility among lineages. Together, our findings suggest that FEM and HOM form a toxin-antidote system that helps establish reproductive barriers.

plant biology↗

bioRxiv2026

Chromosomal evolution and speciation inferred from chromosome-scale genome assemblies in three Cupressaceae species

Chromosome-scale genome assemblies in gymnosperms have lagged behind those of angiosperms, likely due to their large genomes. Coniferous tree species, which belong to the gymnosperms, are important resources for wood production in the forestry industry. To elucidate the evolution and speciation of these species and establish genome resources for breeding, we integrated draft assemblies with optical and genetic mapping to construct chromosome-scale genomes for Japanese cypress (Chamaecyparis obtusa, 8.7 Gb), Japanese cedar (Cryptomeria japonica, 9.6 Gb), and Chinese fir (Cunninghamia lanceolata, 13.4 Gb). Additionally, we assembled and annotated their chloroplast and mitochondrial genomes. Comparative analysis of the nuclear genomes revealed that while synteny is largely conserved, distinct translocations and inversions occurred in chromosomes 2, 6, and 9. Notably, the significantly larger genome of C. lanceolata was associated with frequent tandem gene duplications rather than transposon expansion. These findings suggest that chromosomal rearrangements and segmental duplications played key roles in the divergence of these species. The genomic resources presented here including chromosome-scale sequences, gene annotations, and genetic maps will facilitate advanced conifer genetics and accelerate forest tree breeding programs.

genomics↗

bioRxiv2025

Progeny-based genomic selection reveals untapped genetic potential in an underutilized medicinal plant, Perilla frutescens

O_LIDespite their substantial therapeutic value, medicinal plants have undergone limited genetic improvement through breeding because of the scarcity of expert breeders. Moreover, quantifying bioactive compounds is expensive. Genomic selection (GS), which leverages genome-wide markers to predict breeding values and assemble favorable alleles, offers a practical way to unlock latent genetic potential. As a model case, we evaluated GS in red perilla (Perilla frutescens). C_LIO_LIBuilding on previous work, we implemented a cross-selection strategy that prioritized segregation variance by selecting crosses based on predicted additive genotypic values of the progeny, and evaluated its effectiveness through actual crossing experiments targeting three key medicinal compounds. C_LIO_LIProgeny from GS-based crosses (Crs1-Crs7) outperformed those from phenotypic selection (Crs8) in the G2 generation, demonstrating a higher mean, greater variance, and superior top individuals. The best G2 individual exhibited nearly twofold higher levels of two target compounds relative to the existing cultivar Sekiho. C_LIO_LIThis study provides the first empirical demonstration that GS can improve multiple medicinal compounds in red perilla and highlights the effectiveness of cross-selection based on predicted progeny performance. In addition, the evidence presented here supports the broader application of GS in underutilized medicinal plants. C_LI

genetics↗

bioRxiv2025

Optimizing selection of restriction enzymes for complexity-reduced genome sequencing in plants

BackgroundReduced-representation sequencing, e.g., restriction-site-associated DNA sequencing and genotyping by sequencing, is a powerful and cost-effective method to detect polymorphism and to genotype pools of individuals. However, restriction enzymes employed to the analyses were often chosen in basis on intuition and precedents. ResultsWe propose to apply an in silico analysis to predict gene concentrations in restriction fragments, which are templates of complexity-reduced genome libraries. It also predicts fragment lengths and physical positions in plant genomes. The in silico analysis was verified using actual amplified fragment length polymorphism patterns. The genome-scale differences in the distributions of restriction fragments from methylation-sensitive and resistant enzymes accounted for marker clusters on genetic maps, commonly reported in linkage maps of plants. The in silico analysis, using three combinations of enzymes across four model plants, indicated that the combination of MspI and PstI is remarkably informative for reduced-representation sequencing in terms of fragment length, distribution in euchromatic regions, and gene enrichment. ConclusionsApplication of our in silico restriction analysis provides useful information for optimizing the selection of restriction enzymes in empirical reduced-representation sequencing of genomes of several organisms including not only plants but also animals.

genomics↗

bioRxiv2025

Chromosome-level genome assembly of the gerbera (Gerbera hybrida) using HiFi long-read and Hi-C technologies

Gerbera hybrida is one of the most popular ornamental plants and also serves as a valuable model plant within the Asteraceae family. Here, we report both the nuclear and organellar genome assemblies and annotations of G. hybrida, which was developed through hybridization of two wild species. Sequencing was performed using a combination of PacBio high fidelity (HiFi) reads and chromatin capture reads (Omni-C). The total span of the nuclear genome assembly is 2.32 gigabases, and 99.3% of the sequence assembled into 25 scaffolds, consistent with the known chromosome number. Genome annotation of the nuclear genome identified 36,160 protein-coding genes and 11,572 non-coding transcripts. The mitochondrial genome had 363,511 bp and contains 36 protein-coding genes, 3 rRNAs, and 21 tRNAs, while the chloroplast genome is 151,898 bp in length and includes 85 protein-coding genes, 8 rRNAs, and 37 tRNAs. This reference genome provides a foundational resource for future molecular breeding and genetic research in Gerbera and the broader Asteraceae family.

plant biology↗

bioRxiv2025

Chromosome-scale genome assembly of Malcolmia littorea using long-read sequencing and single-pollen genotyping technologies

Malcolmia littorea, a member of the family Brassicaceae, is adapted to coastal and sandy environments and has become a model in studies of reproductive barriers. However, genomic resources for the species are limited. Here, with the aim of understanding the molecular mechanisms underlying key traits in M. littorea, including its survival under harsh conditions, we present a de novo genome assembly consisting of 10 chromosome-scale sequences. We employed a high-fidelity long-read sequencing technology for genome assembly. To anchor the sequences to chromosomes, we developed a single-pollen genotyping method to construct a genetic linkage map based on SNPs derived from transcriptomes of pollen grains, possessing recombinant haploid genomes. We built a genome assembly consisting of 10 chromosome-scale sequences (214 Mb in total) for M. littorea containing 30,861 predicted genes. A comparative genome analysis and gene prediction indicated that the genome of M. littorea is double the size of the Arabidopsis thaliana genome, consistent with a whole-genome duplication followed by gene subfunctionalization and/or neofunctionalization in M. littorea. This study provides a basis for research on M. littorea, an understudied species with ecological and evolutionary significance.

genomics↗

bioRxiv2025

Tracing genome size dynamics in sharks and rays with inclusive sequence analysis by the Squalomix Consortium

Genomes have maintained stable sets of protein-coding genes during evolution, while chromosome organization and genome size vary drastically. Changes in genome size are often attributed to variable amounts of repetitive sequences, including transposable elements. However, it remains poorly understood how such changes were accommodated while maintaining other genomic components. Elasmobranchs, including sharks, rays, and skates, exhibit high among-species variation of genome size and high within-species variation of chromosome length, offering a unique study system to address the question. In this study, we present the first whole genome sequences of the whitebelly skate with remarkably small genome size among elasmobranchs (2.2 Gb), and the red stingray. These chromosome-scale assemblies enabled the assessment of genomic compositions including centromeres and non-coding elements, which revealed notable profiles of tRNA loci and unbiased intragenomic distribution of transposons in elasmobranch genomes. Comparative analyses across these species revealed a shared genomic architecture characterized by correlations of intergenic and intronic sequence lengths with chromosome sizes, with repetitive element accumulation in elongated regions. We analyzed tandemly duplicated genes with high copy number variability. This genome-wide survey revealed the tendency for more frequent tandem gene duplications along with genome size expansion. We document the batoid HoxC cluster in the red stingray genome, which has undergone extensive repetitive element invasion and co-localizes with the HoxB cluster on a sex chromosome. Our study demonstrates an inclusive analysis encompassing both coding and non-coding regions, adaptable to more species in the taxon and a basis for molecular-level understanding on phenotypic diversity of elasmobranchs.

genomics↗

bioRxiv2025

Relationship Between Open Reading Frame 320, a Gene Causing Male Sterility in Tomatoes, and Cytoplasmic Male Sterility in Potatoes

Cytoplasmic male sterility (CMS) is a phenotype wherein plants cannot develop normal male organs because of mitochondrial genes. Several cytoplasmic sterility factors are suggested to be involved in CMS phenotypes in potatoes (Solanum tuberosum); however, reports on the relevant mitochondrial genes remain scarce. Many potato cultivars carry mitochondrial genes that cause CMS, resulting in pollen sterility, thereby limiting their use as male parents in breeding. Therefore, identifying the causal genes is crucial for potato breeding. In this study, we focused on the T/{beta}-type cytoplasm, the most prevalent genome type of potato worldwide, to explore mitochondrial genes involved in CMS in potatoes. We identified a novel gene, open reading frame 320 (orf320), in potato genotypes with T/{beta}-type cytoplasm by comparing the mitochondrial genomes of potatoes. Functional analysis of tomatoes showed that overexpression of orf320 with a mitochondrial transit peptide induced male sterility phenotypes, including abnormal anther development and pollen abortion. Furthermore, an investigation of orf320 in 126 potato cultivars revealed that this gene is specific to the T/{beta}-type cytoplasm and is absent in investigated cultivars with other cytoplasmic types. These findings provide strong evidence that orf320 is a candidate CMS-causing gene in male sterility of T/{beta}-type cytoplasm, offering valuable insights for future potato breeding.

plant biology↗

bioRxiv2025

Heat stress negatively affects betalain biosynthesis in Amaranthus tricolor through down-regulation of CYP76AD1 and 5GT

Orphan crops are considered essential climatic-resilient genetic resources due to their native adaptability to various ecological environments. Amaranthus tricolor is one of a few common vegetables widely cultivated in tropical and subtropical regions. Strong vigor, abiotic-stress adaptability, and nutrition richness make it an ideal vegetable to provide food and nutrient security for smallholders. However, the breeding efforts depend on the field yield trials because little genomic information or genetic resources can be accessed. To fill this gap, we first used the Illumina and Pacbio sequencing systems to assemble a novel reference genome of A. tricolor using a Japanese variety Bayam. Together with a core collection developed in our previous study, we investigated the genetic mechanism of betalain biosynthesis under optimal and heat-stress conditions. Betalain is an antioxidant phytonutrient commonly appearing in beets and amaranths. As a result, ATR1.0CH03_5131103 which associate with ATR1.0ch03g000565 was identified in the optimal condition. Meanwhile, according to the transcriptomic profiles in this study, ATR1.0ch03g000565 also show significantly differential expressions under control and heat stress conditions, suggesting this candidate gene regulates the optimal performance of CYP76AD1. Meanwhile, among the homologous genes involving in the betalain biosynthesis, CYP76AD1 and 5GT were down-regulated under heat stress conditions; cDOPA was up-regulated. This result suggested heat stress reduces betacyanin biosynthesis through the downregulation of CYP76AD1 and 5GT; despite that the upregulation of cDOPA cannot rescue the decrease of betalain. More molecular experiments are required to address the regulation of these three enzymes.

plant biology↗

bioRxiv2025

Artificial mutations in the nuclear gene encoding mitochondrial RNA polymerase restore pollen fertility in cytoplasmic male sterile tomato

Cytoplasmic male sterility (CMS) and restorer of fertility (Rf) are important traits in F1 hybrid breeding. However, the CMS/Rf system has not been used in tomatoes because of the limited resources of Rf lines. In this study, we performed mutagenesis in tomato CMS seeds and successfully obtained 13 suppressor mutants with pollen fertility. Using bulked segregant analysis and whole-genome sequencing for each suppressor mutant, we detected mutations associated with fertility restoration in the nuclear-encoded gene for the mitochondrial RNA polymerase termed SlRPOTm in four independent mutants created through mutagenesis. Furthermore, we found that the loss of function of SlRPOTm was associated with fertility restoration in the tomato CMS line. Expression analysis of orf137, a tomato CMS-causing gene, revealed that reduced expression of orf137 was associated with fertility restoration in tomato CMS. In addition, F1 plants carrying mutations in SlRPOTm were generated, and tomato fruit formation was comparable to that of normal F1 plants. This study demonstrates for the first time that the loss of function of mitochondrial RNA polymerase contributes to fertility restoration in CMS lines. Furthermore, it is possible to replace various tomato varieties with Rf lines using genome editing technology, which will promote tomato F1 breeding in the future.

plant biology↗

bioRxiv2025

Multiple fertility restorer loci for cytoplasmic male sterility caused by orf137 in tomato

Cytoplasmic male sterility (CMS) in plants is caused by incompatibility between nuclear and cytoplasmic genetic information. Fertility can be restored through the action of fertility restoration (RF) genes, which are usually present in the nucleus. CMS lines of tomato (Solanum lycopersicum) have been developed from asymmetric cell fusions, in these lines, cultivated tomato served as a nuclear donor and its wild relative, S. acaule, as a cytoplasm donor. Although RF genes are present in wild relatives of tomato, no genetic or genomic information on the RF genes is yet available. This study reports an RF genetic locus, RF1, on chromosome 1 of S. pimpinellifolium LA1670 and S. lycopersicum var. cerasiforme LA1673 that was revealed by bulked segregant analysis and sequencing. An additional RF locus, RF2, was identified on chromosome 2 of LA1670. A transgenic approach identified two other candidate genes that also restored fertility. The genomic sequence of S. cheesmaniae LA0166 was assembled using high-fidelity, long-read sequencing technology. Sequence comparisons identified further candidate RF genes on chromosome 1 of S. cheesmaniae LA0166. These results suggested that multiple gene loci control the fertility restoration trait in wild relatives of tomato.

plant biology↗

bioRxiv2025

Optimization of crossing strategy based on the usefulness criterion in inter-population crosses considering different genetic effects among populations

In the breeding programs of self-pollinated plants, achieving genetic improvement in multiple traits can be challenging when relying solely on a single biparental population. Interpopulation crosses are employed to integrate favorable alleles from multiple biparental populations to overcome this limitation. In this context, it is crucial to consider the distinct genetic effects in different populations. In this study, we utilized a selection method based on the usefulness criterion (UC) to identify cross pairs suitable for interpopulation crosses. We expanded this approach to enhance breeding programs accounting for varying genetic backgrounds within the genomic selection framework. Using the medicinal plant red perilla as the study material, we conducted simulations to compare the efficacy of selection based on estimated genomic breeding values with that based on UC. Our findings demonstrate that the proposed method is effective in facilitating the simultaneous improvement of multiple traits, particularly by considerably increasing genetic gains among the top-performing individuals in the population. Furthermore, we provide guidelines for implementing interpopulation crosses, including recommendations for the optimal generation for crossing and the appropriate reference generation for calculating the UC. The results obtained in this study offer valuable insights for small-scale breeding programs aimed at simultaneously enhancing multiple traits through inter-population crosses and are applicable to a wide range of crops, including neglected and underutilized species. Key MessageHerein, a method has been proposed for selecting optimal cross pairs based on the genetic potential of progeny in inter-population crosses, considering different genetic effects among populations.

bioinformatics↗

bioRxiv2025

Unstable anthocyanin pigmentation in Streptocarpus sect. Saintpaulia (African violet) is due to variant selectivity of a single MYB gene

O_LISaintpaulia (African violet) pigmentation is notoriously unstable, particularly following passage through tissue culture, but the instability mechanism is unknown. White-striped petals were thought to be due to epigenetics, but the genes involved are unknown. We confirmed that white stripes result from epigenetic regulation based on the flower color traits of plants obtained from tissue culture. C_LIO_LIGene expression in several plant lines, anthocyanin quantification, bisulfite sequencing, and methylation analyses were used to demonstrate the presence of a single MYB gene responsible for pigment variation. We identified SiMYB2 as the cause of variations in tissue color patterning, and that two RNAs were generated from SiMYB2. SiMYB2-Long was expressed in colored tissues, while SiMYB2-Short was expressed only in non-colored tissues. Functional analyses revealed that SiMYB2-Long is an anthocyanin biosynthesis activator and SiMYB2-Short is non-functional. Exon 3 of SiMYB2 was generated by the insertion of a transposon-like sequence. A mutant lacking the element was obtained from cultivars with non-colored tissues. Anthocyanin content and SiMYB2-Long expression in the mutant were greatly increased compared to wild type. C_LIO_LIOur results suggest that the white-striped petals of Saintpaulia are not formed by periclinal chimeras but thorough the transcriptional selectivity of epigenetically regulated SiMYB2. C_LI

plant biology↗