Biology subjects

Kanaoka, M. M.

Publications and source records attributed to Kanaoka, M. M..

4 recordsLinked to original sources

bioRxiv2026

A visualization framework for cell division activity and orientation in pre-anthesis ovaries of Prunus species

Fruit size and shape, which influence horticultural quality, are determined by the number and the size of the cells in the local region. In fruit trees, however, the difficulty of applying molecular genetic approaches has hindered a detailed understanding of the localization and orientation of cell division in developing fruit tissues. In this study, we established a novel framework to visualize cell division in pre-anthesis ovaries of three drupe crops, peach (Prunus persica), Japanese apricot (P. mume) and the interspecific hybrid Japanese apricot (P. salicina x P. mume), providing clear insight into the spatial distribution and orientation of dividing cells. We systematically optimized a 5-ethynyl-2'-deoxyuridine (EdU) labeling protocol for thick ovary tissues by adjusting infiltration conditions and fixation methods. In addition, electron microscopy combined with wide-view tiling visualization was applied to directly identify dividing cells, including those undergoing chromosome segregation and cell plate formation. By combining with machine learning-based detection, we efficiently and objectively identified dividing cells. Using these complementary approaches, we found that cell division activity was broadly distributed throughout pre-anthesis ovaries in all three crops, without pronounced spatial restriction. In contrast, analysis of division orientation revealed region-specific patterns: cells in the outermost exocarp divided predominantly anticlinally, whereas cells in the mesocarp divided largely periclinally, consistent with subsequent ovary (fruit) enlargement. The integrated framework presented here provides a foundation for understanding the spatial and three-dimensional regulation of fruit development and for future studies in fruit morphogenesis and horticulture.

plant biology↗

bioRxiv2024

Male and female gametophytes meet after winter: Testing the overwintering hypothesis for delayed fertilization in Japanese stone oak

PremiseFertilization delays of nearly a year have been observed in many acorn-producing Fagaceae trees. Despite this long-standing recognition, the underlying mechanisms and adaptive significance of delayed fertilization remain largely unexplored. It has been hypothesized that these prolonged delays may serve as an adaptive strategy, allowing ovules to be fertilized and seeds to develop during more favorable seasons, thereby avoiding the adverse conditions of winter. However, empirical evidence to support this hypothesis is still lacking. MethodsTo test the overwintering hypothesis, we observed the seasonal progression of pollen tube growth and ovule development in Lithocarpus edulis, a species exhibiting two flowering seasons, spring and autumn. We conducted monthly observations of pollen tube growth and ovule development in both spring and autumn flower samples. We employed microtome techniques and scanning confocal microscopy to closely examine the seasonal progression of pollen tube growth and ovule development. ResultsWe found that pollen tubes were arrested at the style-joining site, and ovules remained immature in both spring and autumn samples prior to winter. Following winter, pollen tube regrowth and ovule maturation were synchronized in the subsequent spring in both spring and autumn samples. ConclusionsOur results support the overwintering hypothesis, suggesting that delayed fertilization may serve as an adaptive strategy to ensure fertilization in spring, overcoming the reproductive challenges posed by cold winter conditions. Our study introduces a new avenue for studying the temporal organization of plant reproductive phenology, specifically the alignment of flowering, pollination, fertilization, and fruiting in seasonal environments.

plant biology↗

bioRxiv2019

Fine-scale ecological and transcriptomic data reveal niche differentiation of an allopolyploid from diploid parents in Cardamine

Polyploidization, or whole genome duplication, is one of the major mechanisms of plant speciation. Allopolyploids (species that harbor polyploid genomes originating from hybridization of different diploid species) have been hypothesized to occupy a niche with intermediate, broader, or fluctuating environmental conditions compared with parental diploids. It remains unclear whether empirical data support this hypothesis and whether specialization of expression patterns of the homeologs (paralogous gene copies resulting from allopolyploidization) relates to habitat environments. Here, we studied the ecology and transcriptomics of a wild allopolyploid Cardamine flexuosa and its diploid parents C. hirsuta and C. amara at a fine geographical scale in their native area in Switzerland. We found that the diploid parents favored opposite extremes in terms of soil moisture, soil carbon-to-nitrogen ratios, and light availability. The habitat of the allopolyploid C. flexuosa was broader compared with those of its parental species and overlapped with those of the parents, but not at its extremes. In C. flexuosa, the genes related to water availability were overrepresented among those at both the expression level and the expression ratio of homeolog pairs, which varied among habitat environments. These findings provide empirical evidence for niche differentiation between an allopolyploid and its diploid parents at a fine scale, where both ecological and transcriptomic data indicated water availability to be the key environmental factor for niche differentiation.Significance statement Polyploidization, or whole genome duplication, is common in plants and may contribute to their ecological diversification. However, little is known about the niche differentiation of wild allopolyploids relative to their diploid parents and the gene expression patterns that may underlie such ecological divergence. We detected niche differentiation between the allopolyploid Cardamine flexuosa and its diploid parents C. amara and C. hirsuta along water availability gradient at a fine scale. The ecological differentiation was mirrored by the dynamic control of water availability-related gene expression patterns according to habitat environments. Thus, both ecological and transcriptomic data revealed niche differentiation between an allopolyploid species and its diploid parents.Competing Interest StatementThe authors have declared no competing interest.View Full Text

plant biology↗

bioRxiv2018

Adaptive Reduction of Male Gamete Number in a Selfing Species

The number of male gametes produced is critical for reproductive success and varies greatly between and within species1-3. Evolutionary reduction of male gamete production has been widely reported in plants as a hallmark of the selfing syndrome, as well as in humans. Such a reduction may simply represent deleterious decay4-7, but evolutionary theory predicts that breeding systems could act as a major selective force on male gamete number: while large numbers of sperm should be produced in highly promiscuous species because of male-male gamete competition1, reduced sperm numbers may be advantageous at lower outcrossing rates because of the cost of gamete production. Here we used genome-wide association study (GWAS) to show a signature of polygenic selection on pollen number in the predominantly selfing plant Arabidopsis thaliana. The top associations with pollen number were significantly more strongly enriched for signatures of selection than those for ovule number and 107 phenotypes analyzed previously, indicating polygenic selection8. Underlying the strongest association, responsible for 20% of total pollen number variation, we identified the gene REDUCED POLLEN NUMBER 1 affecting cell proliferation in the male germ line. We validated its subtle but causal allelic effects using a quantitative complementation test with CRISPR-Cas9-generated null mutants in a nonstandard wild accession. Our results support polygenic adaptation underlying reduced male gamete numbers.

evolutionary biology↗