Living in Space
Integral Understanding of life-regulation mechanism from "SPACE"

A novel mechanism for regulating plant root growth under different gravitational conditions in space – Publicly Invited Research 2018－2019

1. A01 Ogura
2. A01 H. Takahashi
3. A01 S. Takahashi
4. A01 Michiue
5. A01 Hinoi
6. A01 Tsumoto
7. A01 Nikawa
8. A01 Chatani
9. A01 Kawakami
10. A01 Akiyama
11. A01 Tomita

1. A02 Shinohara
2. A02 Mieda
3. A02 Maekawa
4. A02 Abe
5. A02 Ohgami
6. A02 Kawano
7. A02 Takano

1. A03 Suzuki
2. A03 Nakamura
3. A03 Harada
4. A03 Kobayashi
5. A03 Miyamoto
6. A03 Funayama
7. A03 Kakinuma

1. B01 Lazarus
2. B01 Kato
3. B01 Kunieda
4. B01 Kitaya
5. B01 Sawano

Research Subject	A novel mechanism for regulating plant root growth under different gravitational conditions in space
Research Group Leader	Hideyuki Takahashi Professor, Graduate School of Life Sciences, Tohoku University Website http://www.ige.tohoku.ac.jp/tekio/ (*Written in Japanese)
Research Collaborator(s)	Akie Kobayashi Assistant Professor, Graduate School of Life Sciences, Tohoku University

Water status and availability critically limit the growth, productivity and survival of plants with sessile nature. Land plants therefore obtained an ability to acquire water via downward elongation of roots in response to gravity and moisture gradients. We have shown that gravitropic response interferes with hydrotropism on the ground, but the two tropisms can be separated in microgravity (Morohashi et al., New Phytol. 2017). To date, it is known that roots display gravitropism by gravity sensing in columella cells of the root cap, which induces asymmetric auxin transport and distribution for the differential growth at the elongation zone. On the other hand, we have revealed that the elongation zone plays a dual role in hydrotropism for both sensing moisture gradients and differential growth (Dietrich et al., Nature Plants 2017). Also, we identified MIZ1 gene indispensable for hydrotropism and found abscisic acid (ABA) to be a positive regulator of hydrotropism (Kobayashi et al., PNAS 2007; Takahashi et al., Planta 2002). Both MIZ1 and ABA signaling function for hydrotropism in cortex at the elongation zone (Dietrich et al., Nature Plants 2017). Thus, molecular mechanism for hydrotropism is unique and differentiated from that of gravitropism, implying that hydrotropoic response can be manipulated or adopted for controlling root growth under altered gravity conditions. However, the sensory mechanism as well as molecular function of MIZ1 and its relationship with ABA signaling remain unknown. Here, we will attempt to 1) identify the apparatus sensing moisture gradients, 2) analyze molecular function and network of MIZ1 – ABA regulation of hydrotropism, and 3) develop a methodology of root architecture formation for plant production in space.