Biology subjects

Toriyama, K.

Publications and source records attributed to Toriyama, K..

6 recordsLinked to original sources

bioRxiv2026

Rice Jumonji706 confers the photoperiod sensitivity in rice by distinct regulation of short-day and long-day flowering time regulatory pathways.

Photoperiod sensitivity (PS) is a key biological response in plants as they adapt to specific environments. Rice (Oryza sativa L.) exhibits a clear PS, as it implements critical phase transition decisions based on PS signals. In this study, we identified a novel PS gene, JMJ706, that is expected to deliver photoperiod-related signals to the flowering-time regulatory network in a day-length-dependent manner. The JMJ706 mutants exhibit early flowering under LD and later flowering under SD compared to WT plants. The gene encodes an H3K9me2 demethylase, and under long-day (LD) conditions, its demethylase activity facilitates the expression of Grain number, Plant height, and Heading-date7 (Ghd7). Since Ghd7 is a floral repressor in LD, it promotes the vegetative phase by delaying flowering. Under short-day conditions (SD), H3K9me2 demethylase activity facilitates Early heading-date 1 (Ehd1) expression, and it acts as a floral accelerator by inducing Heading date 3 (Hd3a) and RICE FLOWERING LOCUS T 1 (RFT1). Furthermore, we propose that the daylength-dependent promotion of target genes (Ghd7 and Ehd1) occurs through demethylation of specific promoter regions at a crucial time window. In addition, JMJ706 may play an important role in regulating plant architecture, including plant height. The natural variation in JMJ706 alleles shows high frequencies across major rice subpopulations, suggesting that JMJ706 could play an important role in the geographical distribution and adaptation of rice cultivars. Our results may add a new layer to the rice flowering-time regulatory pathway, supporting regional adaptation and potential for future breeding.

plant biology↗

bioRxiv2025

Identification of an early-heading mutant in Indonesian native rice cultivar: 'Gemdjah Beton'

Rice is one of the worlds most widely cultivated field crops and a short-day adapted plant. It possesses a complex genetic regulatory mechanism for heading date determination. Gemdjah Beton (GB) is an Indonesian rice cultivar that takes approximately 17 weeks to flower after being transplanted into a rice field in Japan. We isolated early-heading mutant line GB-10 (flowers around two to three weeks early in the field). Under long-day (LD) conditions, GB-10 flowered approximately two weeks earlier than GB. Under short-day conditions, the heading date between GB-10 and GB plants shows no apparent difference. In agreement with the heading date, Hd3a and RFT1 expressions show around a 10-time relative transcript quantity difference under LD conditions in GB-10 compared to GB. Interestingly, Ghd7 expression was significantly reduced in GB-10, which may trigger the Hd3a and RFT1 activation. A bulk segregation analysis indicated that a single nucleotide variant on chromosome 7 was genetically linked to the early heading phenotype of GB-10 lines. Taken together, we reported the successful isolation of GB-10 as an early-heading mutant.

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↗

bioRxiv2022

The mitochondrial genome of Oryza sativa L. cv. Taichung 65 (Poaceae)

A complete mitochondrial genome sequence was determined by a hybrid approach with long- and short-read sequences in a japonica rice cultivar Taichung 65. The assembled mitochondrial genome was 401,060 bases in length and an overall GC content of 43.88% and predicted to harbor 57 protein-encoding, 18 transfer RNA, and 3 ribosomal RNA genes. Phylogenetic and sequence polymorphism analysis indicated that Taichung 65 is classified as typical japonica. The mitochondrial genome resource would serve as a fundamental tool to investigate cytoplasmic male sterility in rice.

genomics↗

bioRxiv2021

Disruption of the mitochondrial gene orf352 partially restores pollen development in cytoplasmic male sterile rice

Plant mitochondrial genomes sometimes carry cytoplasmic male sterility (CMS)-associated genes. These genes have been harnessed in agriculture to produce high-yielding F1 hybrid seeds in various crops. The gene orf352 was reported to be an RT102-type CMS gene in rice (Oryza sativa), although a causal demonstration of its role in CMS is lacking. Here, we employed mitochondrion-targeted transcription activator-like effector nucleases (mitoTALENs), to knock out orf352 from the mitochondrial genome in the cytoplasmic male sterile rice RT102A. We isolated 18 independent transformation events in RT102A that resulted in genome editing of orf352, including its complete removal from the mitochondrial genome in several plants. Sequence analysis around the mitoTALEN target sites revealed the repair of their induced double-strand breaks via homologous recombination. Near the 5' target site, repair involved sequences identical to orf284, while repair of the 3' target site yielded various new sequences that generated new chimeric genes consisting orf352 fragments. Plants with a new mitochondrial gene encoding amino acids 179 to 352 of ORF352 exhibited the same shrunken pollen grain phenotype as RT102A, whereas plants either lacking orf352 or harboring a new gene encoding amino acids 211 to 352 of ORF352 showed partial rescue of pollen viability and germination, although they failed to set seed. These results demonstrated that disruption of orf352 partially restored pollen development, indicating that amino acids 179 to 210 from ORF352 may contribute to the establishment of pollen abortion.

plant biology↗

bioRxiv2020

Maternal DNMT3A-dependent de novo methylation of the zygotic paternal genome inhibits gene expression in the early embryo

De novo DNA methylation (DNAme) during mammalian spermatogenesis yields a densely methylated genome, with the exception of CpG islands (CGIs), which are hypomethylated in sperm. Following fertilization, the paternal genome undergoes widespread DNAme loss before the first S-phase. Paradoxically, recent mass spectrometry analysis revealed that a low level of de novo DNAme occurs exclusively on the zygotic paternal genome. However, the loci involved and impact on genic transcription was not addressed. Here, we employ allele-specific analysis of wholegenome bisulphite sequencing (WGBS) data and show that a number of genomic regions, including several dozen CGI promoters, are de novo methylated on the paternal genome in 2-cell embryos. A subset of these promoters maintains DNAme through development to the blastocyst stage. Consistent with zygotic paternal DNAme acquisition (PDA), many of these loci are hypermethylated in androgenetic blastocysts but hypomethylated in parthenogenetic blastocysts. Strikingly, PDA is lost following maternal deletion of Dnmt3a. Furthermore, a subset of promoters showing PDA which are normally transcribed from the paternal allele in blastocysts show premature transcription at the 4-cell stage in maternal Dnmt3a knockout embryos. These observations uncover an unexpected role for maternal DNMT3A activity in postfertilization epigenetic reprogramming and transcriptional silencing of the paternal genome.

developmental biology↗