Key message
Gene distributions and population genomics suggest artificial selection of
ghd7
osprr37
, for extremely early heading date of rice, in the Tohoku region of Japan.
The ranges of cultivated ...crops expanded into various environmental conditions around the world after their domestication. Hokkaido, Japan, lies at the northern limit of cultivation of rice, which originated in the tropics. Novel genotypes for extremely early heading date in Hokkaido are controlled by loss-of-function of both
Grain number, plant height and heading date 7
(
Ghd7
) and
Oryza sativa Pseudo-Response Regulator 37
(
OsPRR37
). We traced genotypes for extremely early heading date and analyzed the phylogeny of rice varieties grown historically in Japan. The mutations in
Ghd7
and
OsPRR37
had distinct local distributions. Population genomics revealed that varieties collected from the Tohoku region of northern Japan formed three clusters. Mutant alleles of
Ghd7
and
OsPRR37
appear to have allowed rice cultivation to spread into Hokkaido. Our results show that the mutations of two genes might be occurred in the process of artificial selection during early rice cultivation in the Tohoku region.
Rice cultivation was introduced into Japan 3000 years ago and has expanded across the country and encompasses a wide variety of environmental conditions. Here, we elucidated the differentiation of ...the genetic population structure of 1037 rice landraces across Japan. Using 4451 polymorphisms derived from genome-wide analysis of double-digest restriction-site-associated DNA analysis, population genomics including ADMIXTURE and principal component analysis was carried out. These landraces were classified into nine subpopulations based on geographical origin. Massive-scale genotyping and diversity analysis demonstrated that the differentiation of genetic population structure in rice landraces across Japan might consist of two phases, namely western to eastern and southern to northern phases. The differentiation of genetic population structure was detected only in landraces from three geographical regions, Hokuriku, Tohoku, and Hokkaido, as the southern to northern phase. Conversely, differentiation was not observed in landraces from six geographical regions, Kyushu, Shikoku, Chugoku, Kinki, Tokai, and Kanto, as the western to eastern phase. The genetic population structure may have facilitated the expansion of genetic diversity among local regions.
Genome‐wide mutations induced by ethyl methanesulfonate (EMS) and gamma irradiation in the tomato Micro‐Tom genome were identified by a whole‐genome shotgun sequencing analysis to estimate the ...spectrum and distribution of whole‐genome DNA mutations and the frequency of deleterious mutations. A total of ~370 Gb of paired‐end reads for four EMS‐induced mutants and three gamma‐ray‐irradiated lines as well as a wild‐type line were obtained by next‐generation sequencing technology. Using bioinformatics analyses, we identified 5920 induced single nucleotide variations and insertion/deletion (indel) mutations. The predominant mutations in the EMS mutants were C/G to T/A transitions, while in the gamma‐ray mutants, C/G to T/A transitions, A/T to T/A transversions, A/T to G/C transitions and deletion mutations were equally common. Biases in the base composition flanking mutations differed between the mutagenesis types. Regarding the effects of the mutations on gene function, >90% of the mutations were located in intergenic regions, and only 0.2% were deleterious. In addition, we detected 1 140 687 spontaneous single nucleotide polymorphisms and indel polymorphisms in wild‐type Micro‐Tom lines. We also found copy number variation, deletions and insertions of chromosomal segments in both the mutant and wild‐type lines. The results provide helpful information not only for mutation research, but also for mutant screening methodology with reverse‐genetic approaches.
We analyzed the genome sequence of a Japanese pear (Pyrus pyrifolia) to facilitate its genetics and genomics as well as breeding programs, in which a variety 'Nijisseiki' with superior flesh texture ...has been used as a parent for most Japanese pear cultivars. De novo assembly of long sequence reads covered 136× of the Japanese pear genome and generated 503.9 Mb contigs consisting of 114 sequences with an N50 value of 7.6 Mb. Contigs were assigned to Japanese pear genetic maps to establish 17 chromosome-scale sequences. In total, 44,876 high-confidence protein-encoding genes were predicted, 84.3% of which were supported by predicted genes and transcriptome data from Japanese pear relatives. As expected, evidence of genome-wide duplication was observed, consistent with related species. This is the first chromosome-scale genome sequence analysis reported for Japanese pear, and this resource will support breeding programs and provide new insights into the physiology and evolutionary history of Japanese pear.
Radish (Raphanus sativus L., n = 9) is one of the major vegetables in Asia. Since the genomes of Brassica and related species including radish underwent genome rearrangement, it is quite difficult to ...perform functional analysis based on the reported genomic sequence of Brassica rapa. Therefore, we performed genome sequencing of radish. Short reads of genomic sequences of 191.1 Gb were obtained by next-generation sequencing (NGS) for a radish inbred line, and 76,592 scaffolds of ≥ 300 bp were constructed along with the bacterial artificial chromosome-end sequences. Finally, the whole draft genomic sequence of 402 Mb spanning 75.9% of the estimated genomic size and containing 61,572 predicted genes was obtained. Subsequently, 221 single nucleotide polymorphism markers and 768 PCR-RFLP markers were used together with the 746 markers produced in our previous study for the construction of a linkage map. The map was combined further with another radish linkage map constructed mainly with expressed sequence tag-simple sequence repeat markers into a high-density integrated map of 1,166 cM with 2,553 DNA markers. A total of 1,345 scaffolds were assigned to the linkage map, spanning 116.0 Mb. Bulked PCR products amplified by 2,880 primer pairs were sequenced by NGS, and SNPs in eight inbred lines were identified.
We present a near-complete genome assembly of tomato (Solanum lycopersicum) cultivar Micro-Tom, which has been recognized as a model cultivar for fruit research. The genome DNA of Micro-Tom, provided ...by the National BioResource Project (NBRP) Tomato of Japan, was sequenced to obtain 72 Gb of high-fidelity long reads. These reads were assembled into 140 contigs, spanning 832.8 Mb, with an N50 length of 39.6 Mb. The contigs were aligned against the tomato reference genome sequence SL4.0 to establish a chromosome-level assembly. The genome assembly of Micro-Tom contained 98.5% complete BUSCOs and a total of 31,429 genes. Comparative genome structure analysis revealed that Micro-Tom possesses a cluster of ribosomal DNA genes spanning a 15 Mb stretch at the short arm of chromosome 2. This region was not found in the genome assemblies of previously sequenced tomato cultivars, possibly because of the inability of previous technologies to sequence such repetitive DNA. In conclusion, the near-complete genome assembly of Micro-Tom reported in this study would advance the genomics and genetics research on tomato and facilitate the breeding of improved tomato cultivars.
Identifying genes/loci for resistance to pine wilt disease (PWD) caused by the pine wood nematode (PWN) is beneficial for improving resistance breeding in
, but to date, genetic information using ...molecular markers has been limited. Here, we constructed a high-density linkage map using genotyping-by-sequencing (GBS) and conducted quantitative trait loci (QTL) analysis for PWD resistance for the self-pollinated progeny of "Namikata 73," which is the most resistant variety among resistant varieties of
, following inoculation tests with PWN. An S
mapping population consisting of the 116 progenies derived from self-pollination of the resistant variety, "Namikata 73" (resistance rank 5 to PWN), was inoculated with PWN isolate Ka-4 and evaluated for disease symptoms. To construct a high-density linkage map, we used single-nucleotide polymorphisms (SNPs) identified by GBS based on next-generation sequencing technology and some anchor DNA markers, expressed sequence tag (EST)-derived SNP markers and EST-derived simple sequence repeat (SSR) markers, and genomic SSR markers. The linkage map had 13 linkage groups (LGs) consisting of 2,365 markers including 2,243 GBS-SNP markers over a total map distance of 1968.4 centimorgans (cM). Results from QTL analysis using phenotype data and the linkage map indicated that PWD resistance is controlled by a single locus located on LG-3, as identified in a previous study. This locus showed overdominant genetic action in the present study. With the confirmation of
in two different mapping populations (present study and a previous study), the locus associated with this region is thought to be a good target for marker-assisted selection in
breeding programs in order to obtain high levels of resistance to PWD caused by PWN.
mitoTALEN, a mitochondrial genome editing technology, demonstrated that the mitochondrial gene orf137 is responsible for inducing cytoplasmic male sterility in tomato.
The cultivation areas of crops have expanded all over the world into various environmental conditions from their original areas along with human migration after domestication. Here, we demonstrated ...the genetic changes in the adaptation of rice with early heading date from the tropics in the origin of Asian cultivated rice. Rice populations exhibiting early heading date collected from around the world divided into six genetically distinct clusters, E1–E6, by ddRAD-Seq. In addition, sequence variations identified in genes for heading date with large effects,
Grain number, plant height and heading date 7
,
Oryza sativa Pseudo-Response Regulator37
, and
Days to heading 8
showed lineage-specific distribution among the varieties with early heading date. Numbers of loss-of-function alleles in these genes could correlate with early heading date. Mutations for earlier heading date may split off into new varieties and leading to genetic clusters. We proposed a model for the selection for early heading date among cultivated rice varieties with early heading date.
The complex genome of a Japanese radish (Raphanus sativus) cultivar named 'Okute-Sakurajima' with an extremely large edible round root was analysed to explore its genomic characteristics.
...Single-molecule real-time technology was used to obtain long sequence reads to cover 60× of the genome. De novo assembly generated 504.5 Mb contigs consisting of 1,437 sequences with the N50 value of 1.2 Mb and included 94.1% of the core eukaryotic genes. Nine pseudomolecules, comprising 69.3% of the assembled contigs, were generated along with a high-density SNP genetic map. The sequence data thus established revealed the presence of structural variations and rearrangements in the Brassicaceae genomes.
A total of 89,915 genes were identified in the 'Okute-Sakurajima' genome, 30,033 of which were newly found in this study. The genome information reported here will not only contribute to the establishment of a new resource for the radish genomics but also provide insights into the molecular mechanisms underlying formation of the giant root.
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