Project

Greetings from the Research Director, Prof. Tetsuya Higashiyama

Individual cells of multicellular organisms communicate with neighboring and distant cells to maintain the organism. We call such cell-to-cell communication, to coordinate between the whole and a part, "holonic communication". For example, a lizard's tail grows until it reaches the appropriate size and shape during regeneration. We postulate that individual cells learn their position and roles via holonic communication. In recent decades, molecules involved in cell-to-cell communication have been identified in various organisms. However, it is still unclear how these molecules actually behave and work in the living organism. For example, it may be said that "a morphogen controls morphogenesis via its gradient of concentration", but no one has actually addressed how the morphogen changes its spatiotemporal distribution in the living organism and what distribution or change in the distribution of the morphogen is critical for its function.

It is my dream that we will be able to examine the cells and molecules of living material under a microscope with complete control. I call this field of biology "live cell biology" and have been performing live-cell imaging and micromanipulation studies with a view to opening up the field. The combination of cell-manipulation technologies with live-cell analyses sometimes provides breakthroughs. For example, by developing a laser-assisted thermal-expansion micro-injector and using the unique plant species Torenia fournieri, which has a protruding egg apparatus, we succeeded in identifying LURE peptides as pollen tube attractants. Plant scientists have been searching for these for more than 140 years. If we can develop technologies that allow us to manipulate cells and molecules with complete control under the microscope, live cell biology can be achieved. This would make it possible to study holonic communication, which is difficult to examine due to technical limitations. The word "holonics" in the title of our project means the study of relationships between the whole and a part.

In this ERATO project, using plants as models, we will study various developmental processes, including the patterning of the female gametophyte and embryo, and complex, dynamic intercellular signaling in pollen pistil interactions in vivo. To this end, we aim to visualize extracellular signaling molecules in tissue, to manipulate these signaling molecules, to perform single cell analysis to reveal the response of each cell in the tissue, to identify new extracellular signaling molecules, and to develop devices and technologies for these analyses. Three groups have been established for special technology platforms: the optical technology, engineering technology, and single-cell omics groups. The efforts of these three groups, in addition to my own, will contribute to opening up a new frontier in the field of holonic communications.

Optical Technology Group

Our group performs the live cell imaging of plant hormone (auxin), peptide ligands, and small RNA, which are key factors of holonic communications during formation of egg apparatus and embryogenesis. We aim to elucidate the mechanisms of holonic communications during formation of egg apparatus and embryogenesis by using optical manipulation (e.g., regulation of expression of signaling molecules by two-photon laser or infrared laser) and advanced microscopy technologies (e.g., analysis of stimulus response by microinjection under microscope).

Nano-Engineering Group

Final goal of Nano-Engineering Group is to understand a holonic communication between a single live cell and its surrounding live cells by introducing MEMS-based microfabrication, microfluidic, and single molecule technologies to plant cell physiology.
Specifically, tissue culture and observation devices for studying in vivo egg apparatus formation and embryogenesis will be developed toward live cell-to-cell communication imaging at the process of plant reproduction and embryogenesis. Manipulation and measurement techniques with resolutions at the plant cell level and also at the signaling molecule level will be developed to realize single-cell omics. Associated techniques and devices such as mechanical manipulation of cells and molecules, and microinjection enabling stimulation and response measurement will be developed. For example, development of a plan-on-a-chip device, which traps and guides individual pollen tubes in micro-channels, is in progress to realize quantitative study on the effect of LURE protein on pollen tube guidance mechanisms at the molecular level.