新学術領域研「植物多能性幹細胞」

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Research - A02:Selected Projects -

[Core Research Groups A01 A02]  [Selected Projects A01 A02]

A02:Selected Research Projects

Unveiling the developmental principles of plant stem cells by studying the moss, Physcomitrella patens

PI Tomomichi Fujita Graduate School of Science, Hokkaido University

The outwardly growth of protonemal stem cells in mosses allows us to observe them at the unicellular level. Taking advantage of this, we are going to uncover the molecular mechanisms of cell polarity and asymmetric cell division in plant stem cells. To this end, we will study a plant-specific transcription factor that is involved in these developmental processes in the moss apical stem cells. We will also study the mechanism on how the apical stem cells switch between asymmetric and symmetric cell divisions under various challenging environmental conditions. Furthermore, the relationship between cell stemness and plasmodesmata-dependent cell-cell communication will also be explored. Thus our research attempts to tackle the fundamental aspects of stem cell development in plants.

Massive mitochondrial fusion and genome amplification in plant stem cells

PI Sin-ichi Arimura Graduate School of Agricultural and Life Sciences,
The University of Tokyo

Mitochondria undergo fission and fusion constantly. The dominance of fusion makes mitochondria longer or larger, and such enlarged mitochondria are transiently or stably observed in some kinds of plant stem cells. These plant stem cells have multiple hyperploid mitochondria. In contrast, each mitochondrion in somatic cells has DNA on average less than one mitochondrial genome. The relationships of mitochondrial morphology and their genome maintenance in plant stem cells and the physiological meaning of the morphology will be studied by using Arabidopsis and its mutants of mitochondrial morphology.

Visualization of plant hormones with high spatiotemporal resolution accelerating plant stem cell research

PI Tetsuya Kitaguchi Institute of Innovative Research,
Tokyo Institute of Technology

Plant hormones play important roles in plant development, such as proliferation, differentiation, and maintenance of stem cells. However, there are not many sensors visualizing plant hormones with high spatiotemporal resolution under optical microscope. Therefore, visualization of distribution and dynamics of plant hormone in plant stem cells dramatically accelerate not only plant stem cell research but also plant physiology. In this study, we develop plant hormone sensors using Flashbody technology which fuses fluorescent protein and antibody, and detect spatiotemporal dynamics of plant hormones in shoot apical meristem and root apical meristem.

Establishment and maintenance of pluripotent stem cells during plant fertilization and embryogenesis

PI Hidenori Takeuchi Institute of Transformative Bio-Molecules, 
Nagoya University

During angiosperm fertilization process, the egg cell forms into the zygote and acquires “stemness” by fusing with the sperm cell nucleus. The fertilized egg cell, the zygote, starts dividing and developing into embryo in female tissue. In the fertilization and embryogenesis, epigenetic information is dynamically reorganized to establish and maintain “stemness” for proper embryo development. In this study, we analyze epigenome dynamics in developmentally programmed fertilization and embryogenesis processes. We also attempt to identify key factors involved in deposition of the centromeric histone H3 variant CENH3 that is an epigenetic mark essential for proper kinetochore formation. Finally, we aim to understand mechanisms of stem cell establishment and maintenance controlled by epigenome dynamics and chromosome maintenance.

Molecular basis for stemness of the pericycle

PI Tatsuo Kakimoto Graduate School of Science, Osaka University

Lateral roots are produced from pericycle cells, which are located between endodermis and vasculature. In Arabidopsis, xylem-pole pericycle (XPP) cells initiate cell division in response to auxin resulting in production of the lateral root primordium. External application of auxin to a root induces cell division exclusively in XPP. In this project we will carefully rexamine the character of pericycle focusing on cell cycle regulation. Another aim is to identify a regulatory system that govern the stemness of XPP.

Redundancy and cooperativity in termination of floral stem cell activities

PI Toshiro Ito Graduate School of Science and Technology,
Nara Institute of Science and Technology

During flower development, the robust stem cell activities are terminated to produce seeds for next generation. We are studying genetic pathways controlling floral meristem determinacy and showing that multiple genes (transcription factors, epigenetic regulators, signaling molecules and auxin-related proteins) are involved in this process in stage- and cell type-specific manners. We plan to understand the dynamics and functions of auxin in floral meristem determinacy control through molecular genetics analyses. We also plan to grow plants under various environmental conditions (e.g. temperature and light) to study the molecular basis of environmental robustness though genetic redundancy and cooperativity.

Growth regulation and stem cell maintenance in the shoot meristem

PI Mitsuhiro Aida International Research Organization for Advanced Science and Technology,
Kumamoto University

The shoot meristem maintains stem cells at its summit and continuously produces differentiating cells that give rise to shoot organs such as leaves, stems and floral organs. Focusing on the functions of the transcription factors CUC1, CUC2 and CUC3, which are essential for shoot meristem formation, as well as the two classes of their downstream factors KNOX and auxin-related genes, both of which are involved in directional tissue growth, we investigate molecular mechanisms that regulate growth patterns within the shoot meristem and their significance in stem cell maintenance.

Studies on vegetative propagation in semi-aquatic plant, Rorippa aquatica

PI Seisuke Kimura Faculty of Life Sciences, Kyoto Sangyo University

Aquatic plants evolved from land and modified terrestrial features to submerged environments. One of such adaptive features is high ability of vegetative propagation. Vegetative propagation is commonly seen across many of plant species, the regulatory mechanisms involved are largely unknown. Rorippa aquatica is a perennial herbaceous semiaquatic plant. R. aquatica propagate asexually in nature and they can produce new plantlets from the cut site of leaf fragments without external application of phytohormones. We will investigate the mechanism of vegetative propagation in R. aquatica to understand the principles of pluripotent stem cells underlying plant vitality.

Control of stem cell indeterminacy and characterization of intermodal stem cells in rice

PI Katsutoshi Tsuda National Institute of Genetics

Stem cells are generally indeterminate and maintain their mitotic potential, whereas they also need to properly differentiate upon cell fate determination. Hence, control of cell indeterminacy is one of key aspects of the stemness. In plant shoot meristems, KNOX transcription factors prevent stem cell population from differentiation, whereas these TFs are down-regulated where leaves and stems initiate. In this study, we aim to understand how shoot stem cell indeterminacy is maintained and lost during stem development. We study how KNOX TFs are down-regulated during stem differentiation from the SAM. We will also characterize the intercalary meristem, which is maintained by KNOX TFs and expected to harbor stem cells, by using laser-microdissection followed by transcriptome analyses.

Genome stability and change in shoot apical meristem

PI Endo Masaki National Agriculture and Food Research Organization

Maintenance of genome stability in shoot apical meristem may crucial for handing over collect genetic information to the progeny. On the other hand, for adapting themselves to the rapid environmental change, flexible genome change is preferable. In this study, we focus on the response of shoot apical meristem to DNA damage, such as DNA repair, cell cycle arrest, cell death and changing the fate of cells for surviving and try to understand the strategies of plants for survival.