本日のお話�
2019.10.28 at X-NIHONBASHI• なぜ宇宙植物学？�ー背景ー• 植物への重力のはたらき– 重力の「方向」と「大きさ」�ー2つの捉え方ー• 重力の「大きさ」の関わりを調べる実験系– 遠心機による「過重力」– 宇宙実験による「微小重力」�

なぜ宇宙植物学なのか�ー背景ー

植物の重力影響研究�〜生活環の観点から〜�
日本の研究グループ中心に�

GravityDrs. Musgrave, DeMicco?

?

Dr. Kiss

FloweringLife cycle ofland plants

Seedgrowth?
Seedling• 私達の視点
ü 栄養成長?

(wikipedia.org/wiki/
Space Moss• 環境変化に植物は柔軟に対応

ü 二次壁・支持組織�←�抗重力の観点
ü 養水分吸収を担う根系–に着目？

•ü 生殖成長

1.
2.

– 2012宇宙環境利用科学委員会RT活動開始，2014 国際公募に応募– 2015-宇宙環境利用専門委員会コミュニティ，フィジビリティスタディに応募�

→Taiz, Lincoln, and Eduardo Zeiger. "Plant physiology. ed.(1998)

人類の未来�

未知の力を引き出すために植物の重力応答を利用する�

• 氷期は10万年周期(Abe-Ouchi et al, 2013)�

• 古来より建築材料に利用– 重力に抗して進化した結果• しかし，まだまだ植物の未知の機能を引き出せるはず• 成功例→– The Future is Wild，人類消滅後の地球(Dixon & Adams, 2004)�

人類の試練�
• むしろ人為的要因の危惧�–– 温暖化，パンデミック，AI，核（政治の失敗），etc• Pamlin & Armstrong (2015), 12 Risks thatthreaten human civilisation�

Gton(CO2CO25000) Archer and Ganopolski (2005)• 以前に5回の大量絶滅– 破局噴火，天体衝突�
• うち4回は温暖化による�
–（Campbell 生物学 9th ed.）�

– 短期的な視野�(2018)•2050までに人類文明は崩壊– Jared Diamond (2005)�『文明崩壊』�
NHK「ヒトの秘密」（20180302）�

•地球での対策•人類が地球外で生き延びる術を準備�

– 関野吉晴氏「地球永住計画」，SDGs
Campbell
8th ed.
http://sciencewindow.jst.go.jp/html/sw35/sp-002

JAXA含む15カ国の宇宙機関(国際宇宙探査協働グループ ISECG)
国際宇宙探査ロードマップ(GER 3rd, 2018) も出された�

Space farming：重力環境の違い
During journey(c) NASA

Deep space gateway
Lunar surface habitat(Late 2020s ~ 2030s)µG or artificial 1 G(c)NASAon Mars

• Mars human mission:�3 yrs(1 yr exploration)• Food: 2.2 tons per person

Farming in Mars space colony (c)NASA(Yano and Shimazu 2016)• 地球上と同様に育つのか？

"Space crop"

on Regolith

The Martian (c) 20th Century Fox, 2015

Gravitropism: a matter of direction of gravity �Gravity as an environmental factor• Gravitational acceleration vector• Direction: to the center of the earth• Magnitude： 9.81 m/s2 = 1 G
Ø very stable

0.38 G (Mars)
0.17 G (Moon)• Plants need to let– stems grow upward• to obtain sunlight– roots grow downward

makes the earth
spherical (c)NASA• to obtain water and nutrients• Before Newton (1687, Principia), we
did not even notice its presence– by utilizing their sense of thedirection of gravity vector�

Fukaki et al/ Plant Physiology
110.3 (1996): 933-943.

• Is it necessary for plants to perceive it
and adapt themselves to it?
NewtonCambridge University Botanic Garden.

en.wikipedia.org/wiki/Isaac_Newton

根の重力屈性の重力感受部位は根冠�
•

シロイヌナズナの根冠�

根冠を除いて重力刺激（横向きにする）と，重力屈性が生じない

電顕写真
コルメラ細胞
アミロプラスト（球状に近い）• デンプン貯蔵用のアミロプラ
ストの形状は様々•••,,(eds)2003,
Biochemistry &Molecular
Biology of Plants

2012 https://www.alic.go.jp/joho-d/
joho08_000165.html

When a root is placed horizontally, �• A contact site between astatolith and cortical ER• Sedimentation actuallycauses deformation of
an ER membrane• This should lead•

statoliths moveand sediment at
the new bottom.
• And the basal
and lateral sides
are covered withcortical ER.
• What happens
next?

©2009 by American Society of Plant Biologists

Their tomographic analysis
of high-pressure frozen cells �Ø activation of mechanosensitive ion channelsØ Ca2+ response

Leitz, Kang, et al. Plant Cell 2009;21:843-860©2009 by American Society of Plant Biologists

Movement of the statoliths activate mechanosensitive sites in the ER and/or at the plasma membrane leading Ca2+ response�

感受部位と屈曲部位が離れている���messenger は何か？�
••••Leitz, Kang, et al. Plant Cell 2009;21:843-860

Guenther Leitz et al. Plant Cell 2009;21:843-860

chemical messengerの存在はかつてより想定されていた�
中，根冠を除くと生長が少し促進される
右，根冠を片側除くと除いた側の生長が少し促進される
根冠から，下側に生長阻害物質が供給されている証拠�

Taiz, Lincoln, and Eduardo Zeiger. "Plant
physiology. ed.(1998)©2009 by American Society of Plant Biologists

Next: Auxin efflux carrier (PIN3) moves
root: placed
vertically

Auxin is preferentially transported to the bottom side�

root: placed
horizontally

DR5::GUSØcausing inhibition of cell
elongation at this siden usually distributed aroundthe columella cells

n is redistributed to thenew bottom side

Taiz, Lincoln, and Eduardo Zeiger. "Plant physiology. ed.(1998)• The root bends downward�Taiz, Lincoln, and Eduardo Zeiger. "Plant physiology. ed.(1998)

PIN3

This sense of the directionof gravity vector by theendodermis�

In the case of shoot gravitropism�• Statoliths are located in theendodermal (starch sheath) cells

n is also used for"circumnutation" of the stemn important for a climbing
plant to climb up something• 巻き付き茎(つる植物)• 自らを支えるコストを節約

longitudinalmorning glory•

Fukaki et al/ Plant Physiology
110.3 (1996): 933-943.

Ø sedimented at the bottom

アサガオの内皮（デンプン鞘）が欠損した�mutantでは�
転頭
シダレアサガオになる•

Kitazawa et al. Proc

2004

scr�

Arabidopsis WT�

Kitazawa et al. Proc

Kitazawa et al. Proc•

,内皮（デンプン鞘）が欠損すると– （内皮（デンプン鞘）分化に関わるSCRのmutant,scr）
転頭

Next, a matter of magnitude of gravity
Gravity = Mass x Gravitational acceleration(no change)– Plants increase their body massas they grow up– need to resist against increasing
gravity

weeping
type

Gravity• by strengthening their bodies

Ø "Gravity resistance" response– recognition of such a response isof recent years• (Hoson, 2003)

SeedSeedling

Plant

TreeBody mass

Specific structure that strengthens plant body
Cell walls: two typesPrimary cell walls�
Secondary cell walls

STS-95 BRIC-RC• SPACEHAB•),,(eds)(1998)(•

2003,
Biochemistry &Molecular
Biology of Plants• https://jp.discoverlosangeles.com/
blog/lasclerenchyma, fiber• formed during cytokinesis– cellulose– hemicellulose• important for cellelongation• added to primary wall inspecific cell types– lignin• strengthen the body(c) JAXA

二次壁は？�Presumed architecture of the secondary cell wall

STS-95 BRIC-RC••••• Lignin infiltrate the space between cellulose microfibrils andbecome cross-linked

大阪市大のグループ1998年10月– セルロース（鉄筋）の間にリグニン（コンクリート）が沈着• This architecture makes the secondary cell wall strong–3d
シロイヌナズナ胚軸，イネ幼葉鞘�
(Hoson et al. 1999)(Hoson et al. 2002)

Hoson et al. (2002) Plant Cell Physiol
43:1067-1071

Taiz, Lincoln, and Eduardo Zeiger. "Plant physiology. ed." Sunderland: Sinauer Associates
998 (1998): 79.

二次生長する「材」に特徴的

Reaction wood•
• 木材の乾重の20-30%�
• モノリグノールが重合• 合成には多くの酵素が関与••Pine woodIK(from B. G. Bowes, Acolor atlas of PlantStructure)•compression wood–•Rogers and Campbell (2004)

傾いていない場合でも，重力に応答するか？�
�重力を変える単純な方法：Massを増やす�
Gravity = Mass x Gravitational acceleration• 重り（2.5 g， 3 d）を載せる
リグニン化と二次成長が促進

Fiber atlas: Marja-Sisko
Ilvessalo-Pfäffli

tension wood
–Idea: to increase a magnitude of gravitational acceleration�
• Centrifuge ("Rotating arm")• testing for high G when
launching�(C)
Kubota
mfg.
corp.

Uni.
Bremenphoto byIK

• 体重が急に変わる
Ø ストレス応答と切り分けられない• 自然な成長では徐々に重力増加
Ø 重力加速度を変える必要

1-3 glucan

102.5g3Jae-Heung Ko et al. Plant Physiol. 2004;135:1069-1083(C) JAXA

Ames Research Center, Centrifuge, (c)NASAまずは短期の過重力実験�

(2005)Why do we use 300 G ?

Arabidopsis thaliana L. Columbia
LightDark

Grown for20 - 26 daysin the lightpeduncle of 5
mm in length

Pedunclelengthfurther
3 daysControl
1 G,
24 h
Hyper-gravity
300 G,
24 hg• actually not too strongDryweightbasal part ofthe peduncle �Cell wall• Dose response relationships
between gravity accelerationand elongation of azuki beanroot (Soga et al. 2005)• A linear relationship wasobserved

1 G

300 G

used forMicroarray
analysis

were examinedØ Plants show normal response
under even upto 300 G

gSoga et al. Functional Plant
Biology 32: 175–179.

Effect of hypergravity on length and dry weight of the peduncle �(300 G, 24 h, Dark)

5 h treatment

Effect of hypergravity on the content of cell walls in unit lengthof the peduncle�

Isolation of secondary
walls from peduncles
glued

decreased

secondarywalls (mainlyconsisting ofxylem)

increased

Peduncle

Rosette leaf

1%
sumizyme
0.05 %pectolyase*Primary Secondarywallswalls(Tamaoki et al. 2006 J Plant Res 119:79-84)= (Dry weight) (secondary walls)-> Increase of the cell wall

300 G/1 G

Gene Description

C4H 1 gene
4CL 3 genes

At2g30490

2.81
4.24
3.00
2.72

cinnamate 4-hydroxylase (C4H)

1G

AGI No. Fold change

4-coumarate--CoA ligase 2 (4CL2)
At3g21240
4-coumarate--CoA ligase family protein At1g20510
4-coumarate-CoA ligase -like protein At3g48990

FAH 1 gene

ferulate-5-hydroxylase (FAH1)

At4g36220

2.75

OMT 1 gene

O-methyltransferase 1 (OMT1)

At5g54160

2.28

At3g21770
At5g64120
At3g49960
At5g58390
At5g39580
At4g08770
At4g11290
At5g06720
At3g49120

6.85
10.95
9.36
9.27
6.13
4.28
3.48
2.54
2.29

300 G

(Tamaoki et al.
2009 Advances inSpace Research
44: 245-253.)

peroxidase 30
peroxidase, putativeperoxidase, putativeperoxidase, putativeperoxidase, putativeperoxidase, putativeperoxidase, putativeperoxidase, putative
peroxidase, putativecell wall extensibility

isolatedsecondary walls・Monolignol polymerization (9/92)
peroxidase 9 genes(Tamaoki et al. 2006 JPlant Res 119:79-84)

過重力がシロイヌナズナ茎の二次壁�
および（二次壁からなる）木部に与える影響�

Microarray analysis: Expression of lignin-related genes
increased under hypergravity�
・Monolignol synthesis (6/78)＊�*cell walldigestingenzymes(5 d)T(Tamaoki et al. 2006 JPlant Res 119:79-84)

後生木部要素の数・断面積・二次壁の厚さが増加• 二次壁伸展性が低下
Ø ⇒茎が丈夫になる(Nakabayashi et al.
2006 Ann Bot (Lond)
97:1083-1090)•nWhat kind of hormone signaling is involved in thegravity resistance responses?�
•the primary candidate: ethyleneGravity

Ethylene biosynthesis pathway andmicroarray datamethionine

SAM

ACC

ethylene

Gravisensing

Fold changes

MAT3

MAT4

4.0

3.4

ACS6

ACS11

(Tamaoki etal. 2009Advances inSpaceResearch 44:245-253.)

2.1

2.7

EAT1

ACO2

At1g5010

2.3

7.4

7.4

hormone signaling?

gravity resistance
responses

光を当てながら，より長期栽培：過重力栽培装置の開発• 生活環を通じた
過重力影響の調査
富山大学発，特許取得– （久米と唐原，特許第4899052号）– 製作・（株）日本環境計測，（株）松倉（黒部市）
Mori et al. 2017 Biological Sciences in Space 31: 9-13.

Expression of many ethylene biosynthesis genes are upregulated under hypergravity過重力環境：純粋な「実験上の環境」というわけでもない�••••

宇宙緑化・テラフォーミングまで想定すると，コケ�Habitable zone内，Earth Similarity Index (ESI)高地球より大きな系外惑星– Teegarden's star b: (mass x1.1)– GJ 3323 b (mass x2.2)– Proxima Centauri b: 1.14 G– Kepler-452b, 2 G
宇宙開発上，意義はある(c) NASA•「火星改造！ テラフォーミング最前線」（NHK BSプレミアム、2014年2月13日）�

•Christopher
McKay『MakingMars habitable』
ネイチャー�352
巻489号96頁

4https://ja.wikipedia.org/wiki/

https://ja.wikipedia.org/wiki/20191025(c) SETI institute

長期過重力条件下（25d）でのヒメツリガネゴケの成長の変化�

光合成速度，葉緑体への10G影響�

個体数�

シュートと仮根の長さ�

Takemura etal.2017J.
Plant Res.
130:181-192.

シュートの直径�*, P < 0.05;**, P < 0.01;***, P <0.001.
n.s, notsignificant.
8•

過重力下で仮根は長く，茎葉体は短くなり，個体数は増えた．�



Takemura etal.2017J.
Plant Res.
130:181-192.

1 G

Fig. 610 G



1
�

Fig.5

長期に重力を変える（微小重力）実験を可能にした
PI

ISS?

?

2009-2010µG(c) NASA「きぼう」実験棟

1G?

?
(c) JAXA(c) JAXA•

シロイヌナズナを2ヶ月栽培

日本実験棟（JEM）「きぼう」�

軌道上での1 G環境と比較• 微小重力下で生活環を完了させる• 栄養成長・生殖成長は？

(c) JAXA(c) JAXA

Slight differences in thetimings of bolting andflowering under µ G�credit: NASA• 28 d after imbibition• Bolting appeared totake place earlier
under µG
• Opening of the firstflower–

Space 1 GSpace µG

Growth stage No. 6.00 (Boyes et al.)

– Toyama 1 G: 22 d
– Space 1 G: 27 d
– Space µ G: 20 d••

微小重力がシロイヌナズナの茎の成長（栄養成長）に与える影響

国際宇宙ステーション「きぼう」利
用科学実験テーマ 実験成果報
告書
http://iss.jaxa.jp/kiboexp/
theme/first/spaceseed/�

栄養成長／支持組織などへの重力関与，まとめ�• 一次成長– 茎の成長・一次壁の強さは重力に伴い低下• 微小重力から過重力まで，統一的な説明が可能

tua6

Mean ± SE (n = 4 9). �

Ground 1 G Space 1 GµGnnµG(Hoson et al. 2014)
Plant Biol (Stuttg)
16:91-96• 支持組織・二次壁の発達– 繊維を除き，先端部では重力に伴い発達低下（基部ではµG下でも低下しない）– 繊維はµG下でむしろ発達促進傾向• 髄腔の発達促進による茎の強度低下を補うためか？
• 組織・部位により異なる• 微小重力と過重力で統一的な説明はできない

n26 d

Ø

• 二次成長は未調査�Effect of space conditions and microgravity on the morphology of flowers
and siliques (33 d)�

生殖成長，微小重力下での受粉�

Toyama 1G�

• Stigma, µG (33 d)• pollination took place• 国際宇宙ステーション「きぼう」利用科学実験テーマ 実験成果報
告書• http://iss.jaxa.jp/kiboexp/theme/first/spaceseed/�C�

0.5mm�

0.5mm�

0.5mm�

D�

E�

F�

•
•

Flowers were formed under either condition
However, length of siliques appered shorter both under space 1 G and µG••

国際宇宙ステーション「きぼう」利用科学実験テーマ 実験成果報告書
http://iss.jaxa.jp/kiboexp/theme/first/spaceseed/�

＊Silique length (mm)!

6!

生殖器官への宇宙環境の影響（NASA）�

＊
•

(40)
(67)

Values aremean ± SE.

(58)

(53)
(62)

(44)

(15)

(73)

© 2018 Thompson & Morgan
https://www.thompson-morgan.com/p/zinnia-x-hybrida-profusion-orange-gardenready/t72176TM

4!

•下，ISS：Zinnia hybrida cv.
‘Profusion’ Jan. 16, 2016
–0!
99!

9A!

Toyama 1G�

••上，地上：（宇宙試料に近いと思われる）�Zinnia x hybrida 'Profusion
Orange' (Garden Ready)––2!

•Space μG�

B�

Effect of space condition on the length of siliques (62 d)�

8!

Space 1G�

A�

010!

012!

Tsukuba 1G�

007!

008!

Space 1G�002!

– 雌花（舌状花）とその雌蕊は見られるが，両性花（筒状花）が全く見られない

004!

Space μG�

Length of siliques was shorter both under space 1 G and µ G when compared toTsukuba 1 G (*; Nested ANOVA, P<0.05).
国際宇宙ステーション「きぼう」利用科学実験テーマ 実験成果報告書
http://iss.jaxa.jp/kiboexp/theme/first/spaceseed/�

https://www.nasa.gov/image-feature/firstflower-grown-in-space-stations-veggiefacility-0•

器官周辺の微気候（熱対流低下）の影響か�

生殖成長における重力影響�

• 開花期はµG下では早まり，過重力下では遅れる• µGおよび過重力下では，雄性器官は雌性器官より影響を受けやすく，雄蕊が短くなる• seed to seed実験としてµG下での生活環完了には成功• ただし宇宙における（重力条件以外の）環境制御に課題

根の問題�
•

start from a pilot plant (factorylevel）•expand to a farm level– hydroculture– use regolith of moon ormars�

The Martian (c) 20th Century Fox, 2015

6JAXA

12019

RhizosphereRegolith, moon and mars �•

Other factors�
Fertilizers• Chemical (transport)• Organic (recycle)– soil microorganisms• ammonifying,nitrifying bacteria• pathogens– hard to conrtol• (Biosphere2)

moon

Similarities (to earth soil)– nutrient poor
• traces of nitrates andammonium(JAXA/NHK)

mars

•

(NASA/JPLCaltech/MSSS)

Differences– Moon (w/H2O), high pH 9.6• earth, 8.3; mars, 7.3– Mars, high K and C•

Growth exp. using simulant (w/oammonification
nitrification2015
news54 Soilization"

wikipedia/biosphere-2nutrients)

Gravity• 0.17 G (Moon), 0.38 G(Mars)– Mars ≈ Earth > Moon
• Wamelink et al. (2014)PLoS
One 9: e103138.

根に対する重力の影響

トモグラムにおける，シロイヌナズナ個根の同定�

個根への重力影響�• 重力屈性：主根(Baldwin, 2013)・側根(Kuya and Sato,2011)– 閾値は2.0 × 10-3 G以下 (Driss-Ecole

根の基部
ズーム顕微鏡像（実物）とCTスライスを照らし合わせ• 個根の像を同定�
••→Redlightet al., 2008)• 光屈性の重力による阻害– 閾値は0.1 G以下 (Kiss, 2014)µG(Kiss, 2014, Plant
Biology 16: 12-17.)

à月・火星でも根の重力感受は問題ない？

• 水分屈性 (Miyazawa et al., 2012
培地環境への重力影響• 低重力は培地中の水分分布に影響

CTMRIFig. 1. 3D surface model of an
Arabidopsis root constructed byusing a software IMOD (Hutch1data). Bar = 200 µm.

（北宅ら, 2018）

ØØ

Kurogane et al. 2019 Microscopy 68:
i51-i51.

bean Metzner etal. (2015) Plant
methods 11: 17.

Space Moss
2019年7月25日に打ち上げ�

2012年以降「きぼう」で唯一の植物宇宙実験候補�
2015年度採択JAXA 「きぼう」利用フィージビリティスタディ

「宇宙におけるコケ植物の環境応答と宇宙利用（スペース・モス）」�

:•••民間宇宙ベンチャー
実業家のElon MuskのSpaceX社
Falcon 9 ロケット

© SpaceX•

At 6:01 p.m. EDT, or 22:01 UTC,on Thursday, July 25, SpaceX
launched its eighteenth
Commercial Resupply Services
mission (CRS-18) from Space
Launch Complex 40 (SLC-40) atCape Canaveral Air Force
Station, Florida.
• https://www.spacex.com/news/
2019/07/25/dragon-resupplymission-crs-18-launch:(C) JAXA

https://youtu.be/SlgrxVuP5jk

Space Moss arrived at the ISS�

Dragon captured(c) NASA TV
https://twitter.com/AstroHague

Acknowledgements, Collaborators�
•

Ryohei Yamaura, Tomofumi Kurogane, Ryota Sawada, Koshiro Tanihata, Masaki
Muramoto, Shunya Sujishi, Takamichi Suto, Umi Yashiro, Emi Okamoto, DaisukeTamaoki, Seiichiro Kamisaka (Univ. Toyama)••••

Sachiko Yano, Fumiaki Tanigaki (Japan Aerospace Exploration Agency)
Toru Shimazu, Keiji Fukui (Japan Space Forum)
Haruo Kasahara, Daisuke Masuda (Japan Manned Space System Ltd.)
Hirokazu Kasahara (Tokai University), Mitsuhiro Yamada (University of Tokyo)•Takayuki Hoson, Koichi Soga (Osaka City University)•Yoshinobu Mineyuki, Daisuke Yamauchi (University of Hyogo), Kentaro Uesugi,Makoto Hoshino, Akihisa Takeuchi, Yoshio Suzuki (JASRI)••

This study was supported（，）
Experiments were performed with the approval of JASRI (Proposal nos
2014A1265, 2014B1225, 2015B1556, 2016A1390).