Biology subjects

Tsukaya, H.

Publications and source records attributed to Tsukaya, H..

11 recordsLinked to original sources

bioRxiv2026

Rewired meristem regulation drives morphological evolution of the one-leaf developmental system in Monophyllaea glabra

Plants have evolved unconventional shoot systems with a "fuzzy" character that blurs organ boundaries, but the developmental programs driving this morphological diversity remain a mystery. One-leaf plants of the genus Monophyllaea are a striking example of this diversity: they develop a single indeterminate cotyledon instead of a conventional shoot system to form a unique structural unit termed a phyllomorph. Here, we integrate tissue-specific and single-nucleus transcriptomics with spatial gene expression analyses to characterize the meristems underlying this developmental system. The Monophyllaea-specific meristem of the phyllomorph retains a conserved shoot apical meristem-like transcriptional core but has a leaf lamina program superimposed. This chimeric transcriptional state integrates normally distinct developmental programs alongside altered phytohormone regulation. The one-leaf morphology emerges through the rewiring of conserved meristem regulatory networks rather than the passive suppression of meristem activity. The findings highlight the remarkable plasticity of developmental modules in plant morphological evolution.

plant biology↗

bioRxiv2026

The submergence-induced drastic morphological plasticity of root in the amphibious plant Callitriche palustris

Amphibious plants can thrive in both terrestrial and submerged environments, which are fundamentally distinct. Although morphological plasticity of leaf known as heterophylly has been well investigated, the morphological plasticity of root in amphibious plants remains poorly understood. In this study, we discovered that an amphibious plant Callitriche palustris (Plantaginaceae), which has significant heterophylly, has a remarkable morphological plasticity also in root in response to submergence. This species develops thin roots with abundant root hairs, fewer cortical and epidermal cells, and smaller aerenchyma in the terrestrial condition. On the other hand, it develops thicker roots with few root hairs, more cortical and epidermal cells, and larger aerenchyma in the submerged condition. We call this morphological plasticity of root as "heterorhizy". Phytohormone perturbation experiments revealed that abscisic acid (ABA) and gibberellin regulate root hair development and root cell division respectively. We also found the possibility that heterorhizy was acquired in the genus Callitriche. Additionally, a similar form of root hair plasticity was also observed in the phylogenetically distinct amphibious species Ludwigia arcuata (Onagraceae). Furthermore, the absence of root hair development underwater and the similar structure of aerenchyma to C. palustris were broadly seen across diverse aquatic plants. This study provides new insights into the root morphological responses to submerged environments in aquatic plants.

plant biology↗

bioRxiv2026

A live-imaging system for Arabidopsis leaf primordia at early stages

Live imaging is one of the most powerful methods to reveal the morphogenesis of plant organs. However, the highly three-dimensional structure of plant organs always poses technical challenges. For example, the basal region of leaf primordia is rarely observed because of the shape of leaf primordia and the sudden shift in geometry at the point where the leaf primordium connects to the hypocotyl. In this work, we developed a new live-imaging system that is suitable for observing the developmental process of the basal region of Arabidopsis leaf primordia at early stages. Using this system, we achieved continuous observation of the basal region of early Arabidopsis leaf primordia for more than 50 hours.

plant biology↗

bioRxiv2024

Biregional division angles generate sharp apex and concave joints in leaves

Leaf apex, the distal end of the leaf blade, exhibits enormous shape variations across plant species. Among these variations, the sharp apex, characterized by its pointed tip, is important in species identification and environmental adaptation. Despite its taxonomic and ecological importance, the developmental mechanisms underlying the formation of a sharp apex remain unknown. The present study aims to investigate the curvature patterns and morphogenesis of the sharp apex to uncover these mechanisms using Triadica sebifera leaves. Our research revealed that the sharp apex marks the maximum positive curvature, and is flanked by concave joints with negative curvatures, suggestive of differential tissue growth and spatially regulated cellular behavior. Through a combination of wet experiments and numerical simulations, we demonstrated that biregional cell division angles, rather than locally differing cell expansion or division frequency, play a determining role in shaping distinct leaf morphology. Our study highlights the importance of spatiotemporal regulation of cell division angles during leaf development, suggesting that a biregional growth pattern and cellular behavior contribute to diversity in leaf apex morphology.

plant biology↗

bioRxiv2024

Functional conservation and divergence of Arabidopsis VENOSA4 and human SAMHD1 in DNA repair

The human deoxyribonucleoside triphosphatase (dNTPase) Sterile alpha motif and histidine-aspartate domain containing protein 1 (SAMHD1) has a dNTPase-independent role in repairing DNA double-strand breaks (DSBs) by homologous recombination (HR). Here, we show that VENOSA4 (VEN4), the probable Arabidopsis thaliana ortholog of SAMHD1, also functions in DSB repair by HR. The ven4 loss-of-function mutants showed increased DNA ploidy and deregulated DNA repair genes, suggesting DNA damage accumulation. Hydroxyurea, which blocks DNA replication and generates DSBs, induced VEN4 expression. The ven4 mutants were hypersensitive to hydroxyurea, with decreased DSB repair by HR. Metabolomic analysis of the strong ven4-0 mutant revealed depletion of metabolites associated with DNA damage responses. In contrast to SAMHD1, VEN4 showed no evident involvement in preventing R-loop accumulation. Our study thus reveals functional conservation in DNA repair by VEN4 and SAMHD1. One sentence summaryHuman SAMHD1 is involved in dNTP metabolism and DNA repair; the latter function is conserved in VEN4, its likely Arabidopsis ortholog.

plant biology↗

bioRxiv2023

Intronic TNR-retained ISOPROPYLMALATE ISOMERASE LARGE SUBUNIT1 transcripts impair leaf development in Arabidopsis

Intronic trinucleotide repeat (TNR) is widely distributed in plant genomes. In Arabidopsis accession Bur-0, abnormally expanded TTC repeat in intron-3 of the ISOPROPYLMALATE ISOMERASE LARGE SUBUNIT1 (IIL1) gene causes growth defects called the irregularly impaired leaves (iil) phenotype, triggered by DNA methylation-mediated IIL1 gene silencing at elevated temperature. However, little is known about how the reduced expression of IIL1 causes the iil phenotype. We demonstrated that the iil phenotype was resulted from the relative increase of intron-3-retained IIL1 transcripts through the experiments where the iil phenotype was reproduced by introducing the IIL1 gene harboring 100 copies of TTC repeat into Col-0. The iil phenotype appeared when the total amount of the IIL1 transcripts was decreased by co-suppression and the percentage of intron-3-retained IIL1 transcripts was increased. The IIL1 gene encodes an isopropylmalate isomerase large subunit, forming heterodimers with small subunits (AtLeuD1, AtLeuD2, or AtLeuD3). In the myb28 myb29 mutant lacking AtLeuD1 and AtLeuD2, the iil phenotype was almost completely suppressed regardless of higher percentage of intron-3-retained IIL1 transcripts. The results indicated that the iil phenotype was associated with interaction with AtLeuDs, suggesting that intronic TNR-containing transcripts were translated into abnormal proteins and perturbed the metabolic pathway supporting the leaf development.

plant biology↗

bioRxiv2023

Experimental validation of the mechanism of stomatal development diversification

Stomata are the structures responsible for gas exchange in plants. The established framework for stomatal development is based on the model plant Arabidopsis, but diverse patterns of stomatal development have been observed in other plant lineages and species. The molecular mechanisms behind these diversified patterns are still poorly understood. We recently proposed a model for the molecular mechanisms of the diversification of stomatal development based on the genus Callitriche (Plantaginaceae), according to which a temporal shift in the expression of key stomatal transcription factors SPEECHLESS and MUTE leads to changes in the behavior of meristemoids (stomatal precursor cells). In the present study, we have tried to validate this model through genetic manipulation experiments on Arabidopsis. By altering the timing of MUTE expression, we successfully generated Arabidopsis plants with early differentiation or prolonged divisions of meristemoids, as predicted by the model. The epidermal morphology of the generated lines resembled that of species with prolonged or no meristemoid divisions. Thus, the evolutionary process was reproduced via shifting MUTE expression. We also observed unexpected phenotypes, which indicated the participation of additional factors in the evolution of the patterns observed in nature. This study provides novel experimental insights into the diversification of meristemoid behaviors. HighlightGenetic manipulation in Arabidopsis uncovered how changes in temporal gene expression patterns lead to the diversification of stomatal patterns, providing new experimental insights into the evolution of stomatal development.

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

Importance of cell division angle, position of cell proliferative area, and localization of AN3 in lateral organ morphology

Leaf meristem is a cell proliferative zone present in the lateral organ primordia. In this study, we investigated how the proliferative zone affects the final morphology of the lateral organs. We examined how cell proliferative zones differ in the primordia of planar floral organs and polar auxin transport inhibitor (PATI)-treated leaves from normal foliage leaf primordia of Arabidopsis thaliana with a focus on the spatial accumulation pattern of ANGUSTIFOLIA3 (AN3), a key element for leaf meristem positioning. We found that organ shape changes by PATI treatment were correlated to the angle of the cell division plane relative to the leaf primordia axis in the leaf meristem (cell division angle), but not with leaf-meristem positioning, size of the leaf meristem, or the localization pattern of AN3 protein. In contrast, different shapes between sepals and petals compared with foliage leaves were associated with both altered meristem position associated with altered AN3 expression patterns and different distributions of cell division angles. These results suggest that lateral organ shapes are regulated via two aspects: position of meristem and cell division angles Summary statementDifferent lateral organs with different morphology possess different properties of meristems; cell division angles, position of cell proliferative area and AN3 localization patterns.

plant biology↗

bioRxiv2021

A simple Agrobacterium-mediated stable transformation technique for the hornwort model Anthoceros agrestis

We have developed a simple Agrobacterium-mediated method for the stable transformation of the hornwort Anthoceros agrestis, the fifth bryophyte species for which a genetic manipulation technique becomes available. High transformation efficiency was achieved by using thallus tissue grown under low-light conditions. We generated a total of 216 transgenic A. agrestis lines expressing the {beta}-Glucuronidase (GUS), cyan, green, and yellow fluorescent proteins under the control of the CaMV 35S promoter and several endogenous promoters. Nuclear and plasma membrane localization with multiple color fluorescent proteins was also confirmed. The transformation technique described here should pave the way for detailed molecular and genetic studies of hornwort biology, providing much needed insight into the molecular mechanisms underlying symbiosis, carbon-concentrating mechanism, RNA editing, and land plant evolution in general.

plant biology↗

bioRxiv2020

The molecular framework of heterophylly in Callitriche palustris L. differs from that in other amphibious plants

Heterophylly refers to the development of different leaf forms in a single plant depending on the environmental conditions. It is often observed in amphibious aquatic plants that can grow under aerial and submerged conditions. Although heterophylly is well recognized in aquatic plants, the associated developmental mechanisms and the molecular basis remain unclear. In this study, we analyzed heterophyllous leaf formation in an aquatic plant, Callitriche palustris, to clarify the underlying developmental and molecular mechanisms. Morphological analyses revealed extensive cell elongation and the rearrangement of cortical microtubules in the elongated submerged leaves of C. palustris. Our observations also suggested that gibberellin, ethylene, and abscisic acid regulate the formation of submerged leaves. However, the perturbation of one or more of the hormones was insufficient to induce the formation of submerged leaves under aerial conditions. Finally, we analyzed gene expression changes during aerial and submerged leaf development and narrowed down the candidate genes controlling heterophylly via transcriptomic comparisons, including a comparison with a closely related terrestrial species. We revealed that the molecular mechanism regulating heterophylly in C. palustris is associated with hormonal changes and diverse transcription factor gene expression profiles, suggesting differences from the corresponding mechanisms in previously investigated amphibious plants.

plant biology↗