Biology subjects

Minamino, N.

Publications and source records attributed to Minamino, N..

7 recordsLinked to original sources

bioRxiv2023

Comprehensive and quantitative analysis of intracellular structure polarization at the apical-basal axis in elongating Arabidopsis zygotes

A comprehensive and quantitative evaluation of multiple intracellular structures or proteins is a promising approach to provide a deeper understanding of and new insights into cellular polarity. In this study, we developed an image analysis pipeline to obtain intensity profiles of fluorescent probes along the apical-basal axis in elongating Arabidopsis thaliana zygotes based on two-photon live-cell imaging data. This technique showed the intracellular distribution of actin filaments, mitochondria, microtubules, and vacuolar membranes along the apical-basal axis in elongating zygotes from the onset of cell elongation to just before asymmetric cell division. Hierarchical cluster analysis of the quantitative data on intracellular distribution revealed that the zygote may be compartmentalized into two parts, with a boundary located 43.6% from the cell tip, immediately after fertilization. To explore the biological significance of this compartmentalization, we examined the positions of the asymmetric cell divisions from the dataset used in this distribution analysis. We found that the cell division plane was reproducibly inserted 20.5% from the cell tip. This position corresponded well with the midpoint of the compartmentalized apical region, suggesting a potential relationship between the zygote compartmentalization, which begins with cell elongation, and the position of the asymmetric cell division.

cell biology↗

bioRxiv2023

Harnessing deep learning to analyze cryptic morphological variability of Marchantia polymorpha

Characterizing phenotypes is a fundamental aspect of biological sciences, although it can be challenging due to various factors. For instance, the liverwort (Marchantia polymorpha), a model system for plant biology, exhibits morphological variability, making it difficult to identify and quantify distinct phenotypic features using objective measures. To address this issue, we utilized a deep learning-based image classifier that can handle plant images directly without manual extraction of phenotypic features, and analyzed bright-field images of M. polymorpha. This dioicous plant species exhibits morphological differences between male and female wild accessions at an early stage of gemmaling growth, although it remains elusive whether the differences are attributable to sexual dimorphism or autosomal genetic variation. To dissect the genomic factors, we established a male and female set of recombinant inbred lines (RILs) from a set of male and female wild accessions. We then trained deep-learning models to classify the sexes of the RILs and the wild accessions. Our results showed that the trained classifiers accurately classified male and female gemmalings of wild accessions in the first week of growth, confirming the intuition of plant researchers in a reproducible and objective manner. In contrast, the RILs were less distinguishable, indicating that the differences between the parental wild accessions arose from autosomal variations instead of sexual dimorphism. Furthermore, we validated our trained models by an "explainable AI" technique that highlights image regions relevant to the classification. Our findings demonstrate that the classifier-based approach provides a powerful tool for analyzing plant species that lack standardized phenotyping metrics.

plant biology↗

bioRxiv2021

Bryophyte spermiogenesis occurs through multimode autophagic and nonautophagic degradation

Mitochondria change their morphology in response to developmental and environmental cues. During sexual reproduction, bryophytes produce spermatozoids with two mitochondria in the cell body. Although intensive morphological analyses have been conducted thus far, how this fixed number of mitochondria is realized remains unknown. Here, we investigated how mitochondria are reorganized during spermiogenesis in Marchantia polymorpha. We found that the mitochondrial number is reduced to one through fission followed by autophagic degradation during early spermiogenesis, and then the posterior mitochondrion arises by fission of the anterior mitochondrion. Autophagy is also responsible for the removal of other organelles, including peroxisomes, but these other organelles are removed at distinct developmental stages from mitochondrial degradation. We also found that spermiogenesis involves nonautophagic organelle degradation. Our findings highlight the dynamic reorganization of mitochondria, which is regulated distinctly from that of other organelles, and multiple degradation mechanisms operate in organelle remodeling during spermiogenesis in M. polymorpha.

plant biology↗

bioRxiv2021

Identification of a divergent basal body assembly protein involved in land plant spermatogenesis

Oogamy is a form of sexual reproduction and evolved independently in animals, fungi, and plants. In streptophyte plants, Charophyceae, Coleochaetophyceae, bryophytes, lycophytes, ferns (monilophytes), and some gymnosperms (Cycads and Ginkgo) utilize spermatozoids as the male gamete. Plant spermatozoids commonly possess characteristic structures such as the spline, which consists of a microtubule array, the multilayered structure (MLS) in which the uppermost layer is continuum of the spline, and multiple flagella. However, the molecular mechanisms underpinning plant spermatogenesis remain to be elucidated. To identify the genes involved in plant spermatogenesis, we performed computational analyses and successfully found deeply divergent BLD10s by combining multiple methods and omics-data. We then validated the functions of candidate genes in the liverwort Marchantia polymorpha and the moss Physcomitrium patens and found that MpBLD10 and PpBLD10 are required for normal basal body and flagella formation. Mpbld10 mutants exhibited defects in remodeling of the cytoplasm and nucleus during spermatozoid formation, thus MpBLD10 should be involved in chromatin reorganization and elimination of the cytoplasm during spermiogenesis. Streptophyte BLD10s are orthologous to BLD10/CEP135 family proteins, which function in basal body assembly, but we found that BLD10s evolved especially fast in land plants and MpBLD10 might obtain additional functions in spermatozoid formation through the fast molecular evolution. This study provides a successful example of combinatorial study from evolutionary and molecular genetic perspectives that elucidated a function of the key protein of the basal body formation that fast evolved in land plants.

evolutionary biology↗

bioRxiv2021

Remodeling of organelles and microtubules during spermiogenesis in the liverwort Marchantia polymorpha

Gametogenesis is an essential biological event for sexual reproduction in various organisms. Bryophytes and some other plants employ motile sperms (spermatozoids) as male gametes, which self-locomote to the egg cells to accomplish fertilization. Spermatozoids of bryophytes harbor distinctive morphological characteristics, including the cell body with a helical slender shape and two motile flagella at the anterior edge. During transformation from a spermatid to spermatozoid (spermiogenesis), the shape and cellular contents of spermatids are dynamically reorganized. However, how each organelle is reorganized during plant spermiogenesis remains obscure. In this study, we classified the developmental processes during spermiogenesis in the liverwort Marchantia polymorpha according to cellular and nuclear shapes and flagella development. We then examined the remodeling of microtubules and reorganization of endomembrane organelles during spermiogenesis. The results indicate that the state of post-translational modification of tubulin is dynamically changed during the formation of the flagella and spline, and the plasma membrane and endomembrane organelles are drastically reorganized in a precisely regulated manner during spermiogenesis. These findings are expected to provide useful indexes to classify developmental and subcellular processes of spermiogenesis in bryophytes. Summary statementWe classified developmental processes of spermatozoids into 1 + 5 stages and characterized remodeling of organelles and microtubules during spermiogenesis in the liverwort Marchantia polymorpha.

plant biology↗

bioRxiv2020

Switching secretory pathway direction for organelle acquisition in plants

Eukaryotic cells acquired novel organelles during evolution through mechanisms that remain largely obscure. The existence of the unique oil body compartment is a synapomorphy of liverworts that represents lineage-specific acquisition of this organelle during evolution, although its origin, biogenesis, and physiological function are yet unknown. We found that two Syntaxin 1 paralogs in the liverwort, Marchantia polymorpha, are distinctly targeted to forming cell plates and the oil body, suggesting these structures share some developmental similarity. Oil body formation is under the regulation of an ERF/AP2-type transcription factor and loss of the oil body increased M. polymorpha herbivory. These findings highlight a common strategy for the acquisition of organelles with distinct functions in plants, via periodical switching in secretion direction depending on cellular phase transition.

plant biology↗

bioRxiv2019

Periosteum-derived Osteocrin regulates bone growth through both endochondral ossification and intramembranous ossification

During development of long bones, two mechanistically distinct processes contribute to long- and short-axis growth. Endochondral ossification in the growth plate leads to the long-axis growth, while intramembranous ossification including apposition in the periosteum regulates the short axis growth. Here, we show that periosteal osteoblast-derived secretory peptide, Osteocrin (OSTN), promotes both types of long bone growth through potentiation of signaling by C-type natriuretic peptide (CNP), because OSTN inhibits the clearance of CNP by binding to natriuretic peptide receptor 3 (NPR3). The mice lacking OSTN showed less bone mass in trabecular and cortical regions than the control mice, suggesting the dual functions of OSTN in long bone growth. We found that OSTN regulated trabecular bone formation by inducing proliferation and maturation of chondrocytes possibly through enhancing CNP-dependent signaling. Besides the contribution of OSTN to long axis growth, we demonstrated that OSTN together with CNP induced osteoblast differentiation of periosteum-derived multipotent progenitor cells expressing NPR3. These data suggest that OSTN induces long bone growth through endochondral ossification and osteoblast specification of multipotent progenitor cells in the periosteum.

developmental biology↗