Laboratories

Plant Growth Regulation

Outline of Research and Education

Plants continuously produce organs throughout their life. This feature renders them distinct from animals, in which organ formation ceases soon after embryogenesis. We are studying DNA polyploidization and stem cells that support sustained plant growth. We focus on the molecular mechanisms of DNA polyploidization that increase cell volume and organ size, and how plants preserve stem cells. We aim to understand the regulatory system underlying continuous plant growth, and to develop technologies to increase plant biomass and food production.

Major Research Topics

Mechanisms of induction of DNA polyploidization

In many plant species, cells start endoreplication after the cessation of cell division. This is an alternative type of the cell cycle, lacking mitosis and cytokinesis. As a result, DNA content in individual cells is elevated. The resultant DNA polyploidization causes enlargement of individual cells and organs (Fig. 1); thus, it greatly contributes to plant biomass production. However, the induction mechanisms of endoreplication have remained largely unknown. We recently found that regulation of chromatin structure as well as the cell cycle play essential roles in triggering endoreplication. Therefore, we are studying the epigenetic control of endoreplication, and developing technologies to induce DNA polyploidization, which may increase crop yield and woody biomass production (Fig. 2).

Maintenance of plant stem cells

The sequoia, the largest tree on the earth, has a life span of more than 3,000 years. It continues to grow throughout its lifespan, indicating that pluripotent stem cells function for a long time period under changing environmental conditions. How plants generate, proliferate, and maintain stem cells in tissues, however, remains elusive. We are studying the mechanisms of how the stem cell niche is regenerated through reprogramming, and how stem cells are replenished when they are lost owing to environmental stresses (Fig. 3). Our study will shed light on the pluripotency of stem cells and the process of tissue regeneration.

References

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Fig.1
Fig. 1 Epidermal cells of an Arabidopsis leaf.
Each cell type has different DNA ploidy; stomatal cells (2C, red), trichomes (32C, green), and the other cell types (4C-16C). As the DNA content is elevated by endoreplication, the cells are enlarged.
Fig. 2
Fig. 2  Development of technologies to increase the yield of crops and woody biomass by induction of DNA polyploidization.
Fig. 3
Fig. 3 Regeneration of stem cells in roots.
(Top) When the stem cell niche is removed by cutting the root tip, plants regenerate the stem cell niche through reprogramming. (Bottom) Environmental stress causes stem cell death, which is followed by division of quiescent center (QC) cells (white cells) to replenish stem cells.
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