Biology subjects

Nasuda, S.

Publications and source records attributed to Nasuda, S..

5 recordsLinked to original sources

bioRxiv2026

Reduction of Pollen Number and Anther Length in Bread Wheat Studied by a Nested Association Mapping Population

The number of pollen grains, which carry male gametes in seed plants, has attracted interest in genetics, evolution, and breeding. Rapid evolutionary reductions in pollen number and anther length were reported in selfing species as well as domesticated species, although this poses a challenge for hybrid breeding. Here, we studied the variation of pollen number and anther length of the hexaploid bread wheat (Triticum aestivum) by employing a quick pollen counting method. Pollen numbers in cultivars were lower than those in landraces among 54 lines of diverse geographic origins. Using the year of registration of traditional and modern cultivars, we found a reduction in pollen number over the past 150 years. We detected high heritability and variation among Asian landraces and cultivars. Thus, we conducted QTL mapping of pollen number as well as of anther length using nested association mapping lines in which Norin 61 was the common parent. Genomic loci encompassing Green Revolution genes (Rht-B1, Rht-D1, and Ppd-D1) showed significant effects on pollen number and anther length, but their contributions were relatively minor. Although anther length has often been used as a proxy for pollen number in bread wheat, our data showed that their correlations are not necessarily high. Interestingly, we identified a new QTL of pollen number that was not detected by measuring anther length, and, vice versa, a new QTL specific to anther length. These data suggest that pollen number has reduced rapidly in bread wheat but can be modified using the genetic diversity of landraces. Significance statementWe found that modern cultivars of bread wheat have reduced pollen number and shorter anther length, which are common in domesticated species but can be a challenge for hybrid breeding. Using underutilized Asian landraces and cultivars, we reported that new quantitative trait loci as well as loci used in the Green Revolution, are responsible for the traits, which can be employed to increase pollen numbers.

plant biology↗

bioRxiv2026

The juvenile-to-adult phase transition in wheat is independent of the winter-spring growth habit regulated by VRN1

In plants, the juvenile-to-adult (JA) phase transition occurs during the vegetative stage with drastic morphological and physiological changes. Common wheat (Triticum aestivum L.) has a molecular mechanism regulating the duration of vegetative growth in response to cold accumulation, and its sensitivity varies among varieties (winter-spring growth habit) predominantly due to VRN1 genotypes. However, the association of the growth habit with the JA phase transition remained unclear. Here, we investigated temporal changes in shoot apex and leaf morphology, and in the expression of the JA phase transition regulators miR156 and miR172, in winter and spring varieties and VRN1 near-isogenic lines (NILs) under controlled growth conditions, and leaf morphology under field growth conditions. Under controlled conditions, the results indicated that the timing of JA phase transition completion varied among spring varieties without association with VRN1 genotypes. All NILs underwent the JA phase transition at the same timing, and the expression levels of miR156 and miR172 were unrelated to VRN1 expressions during the vegetative stage. The field evaluation of leaf morphology revealed that the phase transition timing was consistent regardless of the sowing timings. These results suggested that the JA phase transition regulatory pathway and the vernalization regulator VRN1 are independent in wheat. HighlightThis study shows that the timing of the juvenile-to-adult phase transition in wheat is not affected by the expression of VRN1, the master regulator of vernalization.

plant biology↗

bioRxiv2024

Modeling of transcriptomic variation among subgenomes in 25 accessions of common wheat reveals cis- and trans-regulation architectures

Common wheat is an allohexaploid plant, thus making it difficult to obtain homoeolog-distinguished transcriptome data. Lasy-Seq, a type of 3 RNA-seq, is efficient for obtaining homoeolog-distinguished transcriptomes and can thus overcome this measurement difficulty. This study obtained transcriptome data from the seedlings, second leaves, and root tips of 25 lines from mainly eastern transmitted area using Lasy-Seq. Roots and seedlings exhibited similar transcriptome profiles; however, they were different from those of the leaves. We determined the effects of subgenomes, lines and their interactions with leaves, roots, and seedlings on the expression levels of each homoeolog triad. Of the 19,805 homoeolog triads, 50.9-55.4%, 24.2-29.5%, and 7.7-9.0% showed significant effects on their expression levels from subgenome, line, and interaction, respectively. 51-55% and 24-30% have genetic variation in the cis- and trans-regulation. Hierarchical clustering and co-trans regulation network analysis of homoeolog triads revealed that the patterns of expression polymorphisms among the lines were shared in different genes. The triads in which the statistical model detected as line effects imply that expression variation between lines is caused by changes in a smaller number of common trans-factors. We assigned gene ontology (GO) terms of the Arabidopsis orthologs to wheat homoeolog triads via reciprocal BLAST between common wheat and Arabidopsis, thus improving the percentage of gene-assigned GO terms to all analyzed GO terms from 19.1% to 90.6%. GO term enrichment analysis revealed that GO terms related to each tissue type function were enriched in genes expressed in the leaves and roots. Our information provides fundamental knowledge for the future breeding of plants possessing complex gene regulatory networks such as common wheat.

plant biology↗

bioRxiv2024

De novo annotation of the wheat pangenome reveals complexity and diversity of the hexaploid wheat pan-transcriptome

Wheat is the most widely cultivated crop in the world with over 215 million hectares grown annually. However, to meet the demands of a growing global population, breeders face the challenge of increasing wheat production by approximately 60% within the next 40 years. The 10+ Wheat Genomes Project recently sequenced and assembled to chromosome level the genomes of nine wheat cultivars to develop our understanding of genetic diversity and selection within the pan-genome of wheat. Here, we provide a wheat pan-transcriptome with de novo annotation and differential expression analysis for these wheat cultivars, across multiple different tissues and whole seedlings sampled at dusk/dawn. Analysis of these de novo annotations facilitated the discovery of genes absent from the Chinese Spring reference, identified genes specific to particular cultivars and defined the core and dispensable genomes. Expression analysis across cultivars and tissues revealed conservation in expression between a large core set of homeologous genes, but also widespread changes in subgenome homeolog expression bias between cultivars. Co-expression network analysis revealed the impact of divergence of sub-genome homeolog expression and identified cultivar-specific expression profiles. In a case study utilising both the newly constructed wheat pan-genome and pan-transcriptome we demonstrate prevalent variation in the prolamin superfamily and immune-reactive proteins across the pan-cultivars.In summary, this work provides both a valuable resource for the wider wheat community and reveals diversity in gene content and expression patterns between global wheat cultivars.

genomics↗

bioRxiv2023

Evolution of wheat blast resistance gene Rmg8 accompanied by differentiation of variants recognizing the powdery mildew fungus

Wheat blast, a devastating disease having spread recently from South America to Asia and Africa, is caused by Pyricularia oryzae pathotype Triticum which emerged in 1985. Rmg8 and Rmg7, genes for resistance to wheat blast found in common wheat and tetraploid wheat, respectively, recognize the same avirulence gene, AVR-Rmg8. Here, we show an evolutionary process in which resistance gene(s), which had obtained an ability to recognize AVR-Rmg8 before the differentiation of Triticum and Aegilops, has expanded its target pathogens. Molecular cloning revealed that Rmg7 was one of alleles of Pm4 (Pm4a), a gene for resistance to wheat powdery mildew on 2AL, whereas Rmg8 was its homoeolog on 2BL ineffective against wheat powdery mildew. Rmg8 variants with the ability to recognize AVR-Rmg8 were distributed not only in Triticum spp. but also in Aegilops speltoides, Ae. umbellulata, and Ae. comosa. This result suggests that the origin of resistance gene(s) recognizing AVR-Rmg8 dates back to the time before differentiation of A, B, S, U, and M genomes, that is, [~]5 million years before the emergence of its current target, the wheat blast fungus. Phylogenetic analyses suggested that, in the evolutionary process thereafter, some of their variants gained the ability to recognize the wheat powdery mildew fungus and evolved into genes for resistance to wheat powdery mildew.

plant biology↗