Research

“Paths are made by walking.”

--Franz Kafka -

Plants, which live their entire lives on the ground where they sprout, need to endure inconvenient environments without moving away. This has given plants a really sophisticated developmental and environmental response during evolution. In order to clarify the mechanisms of plant development and environmental responses, we focus our research on "keeping an eye on living cells".

Mechanism of plant organelle positioning

The plant body is composed of cells with organelles that support cellular functions (Figure A). The number of organelles is controlled by the cell and is known to be distributed in the right "place" at the right "time" depending on the differentiation state and external environment. This suggests that the arrangement of cellular organelles is important for the expression of cellular functions, but how their distribution is determined is largely unknown. We mainly use mosses (Figure B) to visualize the cytoskeleton (Figure C) and synthetic organic chemical probes (Figure D) to focus on the mechanism and function of placing the right number of organelles in the right place at the right time.

Mechanism of plant cell elongation

Plant cells maintain an intracellular pressure that pushes the cell wall outward, which is called turgor pressure. The turgor pressure plays an important role in plant cell elongation.In particular, pollen tubes and root hairs have partially soft cell walls and exhibit a mode of elongation called tip growth, in which only the apical portion of the cell elongates. In nature, it is thought that tip growing cells encounter situations where they must pass through very narrow gaps. For example, pollen tubes elongate through narrow spaces in female tissues for fertilization (Figure E), and root hairs elongate through narrow spaces in soil particles to absorb water and nutrients (Figure F).We fabricated microfluidic channels that are smaller than the cells and studied the behavior of the tip-growing cells (Figure G), and found that they are able to elongate through a gap of 1 micrometer and, in the case of moss protonemata, divide. We are now studying the mechanism of this flexible and powerful response by live cell anyalysis (Figure H).

Construction of plant hormone flow atlas

Plant hormones are involved in the development, differentiation, and growth processes of plants, as well as their responses to the external environment (Figure I). Auxin, in particular, has been predicted to exist for 140 years, and the phototropism of plant shoots toward light is explained by a polar transport model in which auxin moves in the opposite direction to light to promote cell elongation (Figure J). A lot of auxin regulators have been identified and molecular tools for auxin distribution have been developed (Figure K).However, the cell-to-cell movement of auxin itself has not yet been captured. Therefore, we developed a fluorescent auxin together with synthetic organic chemists. By directly observing the cell-to-cell movement of plant hormones, we would like to contribute to the construction of a plant hormone flow atlas (Figure L).

　　The above are just a few of our research themes. In addition to molecular biology and biochemistry experimental facilities, we have microbeam irradiators and infrared observation microscopes for photobiological analysis . We also have access to state-of-the-art imaging equipment at the Nagoya University Live Imaging Center, which I manage. In addition, we can routinely use technologies from different fields, such as microfluidic channel and synthetic chemical probes. We welcome the participation of those who are interested in the above themes, those who want to find phenomena that no one knows yet and pursue their molecular functions, and those who want to further develop your current research themes using state-of-the-art imaging technology, microfabrication technology, and organic fluorescent probes.

How plants exert their regenerative power

We are trying to elucidate the mystery of the amazing regenerative power of plants. A fertilized egg, which is formed when an egg cell and a sperm (sperm cell) are fertilized, divides and produces various differentiated cells that play special roles. Cells that can produce various differentiated cells, like a fertilized egg, are called pluripotent stem cells. On the other hand, differentiated cells with special roles can also become pluripotent stem cells if the environment is right. This phenomenon is called reprogramming. Plants are thought to be easy to reprogram because they can grow shoots from stumps (Figure M) and grow by cuttings. In particular, the moss Physcomitrella patens has an extraordinary high reprogramming ability. In the stem thallus of Physcomitrella patens (Figure N), cells that have differentiated into leaf cells no longer divide. However, if a single cell is extracted, it becomes a stem cell and begins to divide (Video N). By continuing to observe the subsequent developmental process, it was found that the plant regenerates into an individual plant with leaf cells again ( Sato et al. 2017 Sci Rep 7 1909 ). On the other hand, when two adjacent cells are extracted, only one of them will become a stem cell (Video P). It is thought that cells that have become stem cells suppress the stem cell formation of adjacent cells, but what exactly is the mechanism behind this? There are still many details that are not known about the mechanisms of stem cell formation and the mechanisms that suppress stem cell formation. Understanding the mechanism of stem cell formation will help solve various problems in plant breeding and ultimately lead to improved production efficiency of agricultural crops. Therefore, we are working to unravel the mysteries of plant stem cells by making full use of single-cell analysis equipment and AI robotics technology.

The above are just a few of the research themes. In addition to molecular biology and biochemistry experimental equipment, the laboratory is equipped with a microbeam irradiation device and an infrared observation microscope to induce and observe photoreactions. We also have access to cutting-edge imaging equipment from the Nagoya University Live Imaging Center, where Sato serves as center chief. Furthermore, we can routinely use interdisciplinary technologies such as microfluidic channel creation using microfabrication technology and new fluorescent probe development using organic synthesis technology. We welcome participation from those who are interested in the above themes, those who want to discover untouched phenomena and pursue molecular functions that no one has yet discovered, and those who want to further develop their current research themes using cutting-edge imaging technology, microfabrication technology, organic fluorescent probes, etc.