Diameter of the Earth = 13,000 km

From 「みずものがたり」 (Mizu-monogatari, in Japanese)

Advances in Plant Stress #6Topic in water stress regulation in plant

(Earth water globe)

(salt water)

(fresh water)

(ice)

(ground water)

(lakes)

(soil water)

(rivers)

Mainly used this only 0.01%

Water stress

• Global shortage of available water and drought

• Osmotic aspect of salinity stress• Molecular mechanism of water

transport: Aquaporins

You can download this presentation (pptx-file) from the site:http://www.rib.okayama-u.ac.jp/MolecularPhysiology/katsuhara/katu_e.html

Global water crises

Water demand and use form

http://www.unep.org/dewa/vitalwater/article43.html

Global water crises • Increase of population

and social development

• Shortage of water for life and agriculture

• Water pollution (Less quality)

• Population in flood area

Scientific AmericanAugust, 2008

In this issue, it was mentioned that “10% reduction of irrigation water saves water more than all other uses”

Canal for agriculture

Shrink of Aral Sea(Central Asia)

60 Km

朝日放送（テレビ朝日系） 2008 年 3 月 9日放送

http://kobajun.chips.jp/wp-content/uploads/022702.jpg

Map: The Shrinking Ogallala Aquifer

http://www.circleofblue.org/waternews/2014/world/map-shrinking-ogallala-aquifer-1950-2011/

Even Without a Drought, We’re Depleting Groundwater at an Alarming Pace

http://modernfarmer.com/2015/07/ogallala-aquifer-depletion/

No more ground water until 2050

Over 1 billion people live in areas where groundwater is disappearing faster than it can be replenished.http://inhabitat.com/new-study-finds-groundwater-demand-outstrips-supply-for-over-1-billion-people/

http://sanfrancisco.cbslocal.com/photo-galleries/2015/04/09/california-drought-2015/

California Drought

http://www.agweb.com/blog/Know_Your_Market_281/drought_concerns_mounting_in_new_zealand_and_california_/

from Global Risk Report (January 15, 2015) http://www.weforum.org/reports/global-risks-report-2015

World Economic Forum

By Dr. Richard Errett Smalley (2003 ）　　 Novel Prize, Chemistry 1996

A Puzzle for the Planet

Scientific American 312, 62 - 67 (2015)

The world is trying to improve energy, water and food supplies individually, but the challenges need to be solved in one integrated manner. That approach will also benefit the environment, poverty, population growth and disease.

• Plant scientists can contribute to the solution to this global water crisis and food production via crops requiring less water.

• 10% reduction of irrigation water saves more than all others（ Scientific American 2008, previous issue)

Water

Earth scienceEnvironmental science

Social, economic,

political science

Engineering

Plant and agricultural science

Salinity and water stress

From “The use of saline waters for crop production” FAO paper 48 (1992)

Salt-affected land

Dry landSaline soil

Saline soil distribution overlaps with dry land

Bad water (saline water)

Death Valley 　(USA)

High evaporation 　→　 Drought　↓Salt remains 　→　 Salt stress

Water with high salt

Sanyo NewspaperApr. 3, 2011

Tsunamai

MineralWater Na+↑

Mineral

Water↓

Na+

Water(Dehydration)

• Arid and semi-arid area <dry land> (high evaporation)

• Coastal area (sea water)• Underground salt

New South Wales (Australia)

Raising saline ground water

We must manage water use adequately.

Can We Feed the World & Sustain the Planet? Scientific American 2011 日本語版日経サイエンス　２０１２年３月号「人口７０億人時代の食糧戦略」　

The world must solve three food problems simultaneously: end hunger, double food production by 2050, and do both while drastically reducing agriculture's damage to the environment.

http://www.nature.com/scientificamerican/journal/v305/n5/full/scientificamerican1111-60.html

Can We Feed the World & Sustain the Planet? Scientific American 2011 日本語版日経サイエンス　２０１２年３月号「人口７０億人時代の食糧戦略」　

http://www.nature.com/scientificamerican/journal/v305/n5/full/scientificamerican1111-60.html

Five solutions, pursued together, can achieve these goals: (1) stop agriculture from consuming more tropical land, (2) boost the productivity of farms that have the lowest yields, (3) raise the efficiency of water and fertilizer use worldwide, (4) reduce per capita meat consumption and (5) reduce waste in food production and distribution.

Approach from Plant Science　 Drought/salt tolerance (efficient/less water usage)

Mechanism of water uptake/transport

Salinity stress

Osmotic stressIonic stress(K+ deficiency ／ excess Na+ influx)

Inhibitions of: water uptakecell elongationleaf development

Dehydration

Recovery/Adaptation

Ion homeostasisNa+ extrusion/compartmentation/K+ reabsorption

Osmotic adjustmentAccumulations of ions/solutes/organic compounds

<Signal transduction>

(Cell death)

Inhibitions of: photosynthesisprotein synthesisenzyme activity

Na+ toxicity

A schematic summary of the stresses that plants suffer and resultant responses of plants to detrimental effects for survival under drought and high salinity.

Drought stress

Aquaporin

Molecular transport of water transport　・・・　 depends on water potential

deference“Water potential” mainly consists in

“concentration” and “presser”

「 Semi-permeable membrane 」Water can pass but solute (M) cannnot

Power of Swelling

Physical presser need to stop swelling （ P)

Physical static presser :「 Presser potential 」 ψp

・・・” osmotic presser”　　（ proposal to concentration ）⇒ 　「 Osmotic potentail 」 ψosm

minus (osmotic pressure)

Why minuis ？　　 ψp ＋ ψosm ＝０　（ balance drnamic equation ）

MWater molecule

P

P

ψosm: -0.1 > -0.5(MPa)

Water moves from high ψw to low ψw

ψp: 0 < 0.4(MPa)

Water potential ψw = ψosm + ψp

ψ1 ψ2

Water movement

This is “Turgor” in plant cells 1 MPa ≈ 0.4 mol/litter ≈ 10 atm （気圧）

ψosm -0.1 > -0.5ψp 0 < 0.4

ψ -0.1 = -0.1

(ψ1 = ψ2)

+

+ ・・・

P

ψ1 ψ2ψ1 ψ2

Animal cells Plant cells(View from water potential)

細胞膜 Plasma-membrane 細胞壁 Cell wall

• Inner ψosm = Outer ψosm• Inner ψw = Outer ψw

• Inner ψosm ≠ Outer ψosm• Presser at call wall• Inner ψw = Outer ψw

At low water potential of soil (drought/ salt stress)

Water potential

－　 0 　 pure water

Wet

Soil Root

Weak drought/salt stress

soil Root

Strong drought/salt stress

soil Root

Osmotic adjustment= reduce cellular ψw

= reduce cellular ψosm

= increase osmotic presser

ψw

Water potential soil Root Soil root

ψw

Dehydration

Compatible solute 　→ (osmtic compounds)

• Increase osmotic presser• Chaperon activity• Scavenging activity

Betaines: tri-methyl amino acidsH3N+- → 　 (CH3)3N+-

Proline:

Example;Tobacco cells under salt stress

At low water potential of soil (drought/ salt stress)

Water potential

－　 0 　 pure water

Wet

Soil Root

Weak drought/salt stress

soil Root

Strong drought/salt stress

soil Root

Osmotic adjustment= reduce cellular ψw

= reduce cellular ψosm

= increase osmotic presser

ψw

Water potential soil Root Soil root

ψw

PreventIncrease

permeability

Water uptake （ movement/flux ）：

Water flux* ＝ Driving force×water permeability ( 駆動力） （水の動きやすさ：透過性）（ *per unit time ）

Driving force:Water potential difference （ Dam: gravity potential ）In plant, mainly,

Difference of ψosm

Permeability/conductance:（ Dam: opening of gate ）In plant, mainly,

Activity of aquaporins

Water uptake （ movement/flux ）：

Water flux* ＝ Driving force×water permeability ( 駆動力） （水の動きやすさ：透過性）

Water potential difference

Surface area×Water permeability per unit area　（表面積）　　　　　　　　　　　　（面積当たりの水透過性）　

Aquaporin determins this• All bacteria, animal and plants• Membrane proetin with about 300 amino acids• Two Asn-Pro-Ala motif

（ *per unit time ）

Symplastic pathApoplastic path

Aquaporins are required for water across the membrane via symplastic path

Soil water

root

casparian stripe (not permeable)

xylem

Water is most abundantly used in cells.Aquaporin is a water transporter. → Aquaporins regulate largest transport.

Regulation by; humiditiy, salt stress, light, temeperature, others

LocalizationPlasmamembrane ( ＰＩＰ）Tonolast membrane（ＴＩＰ）Peribacteroid memebrane or plasamamembrane (NIP)ER membrane (SIP)

Gene family: >30 genesSubstrates: 　　　 H2O 、 CO2 、 H2O2, B ・・・）

aquaporinaquaporin

生体膜

Output; Stress tolerance, growth regulation, Post-harvesting…

Regulatory regions

Aquaporins ; 1) increase membrane water

permeability2) make it possible to regulate

water permeability

Structure in the membrane

Open/closeIntracellular trafficking

Murata at al. (2000) 　 Nature 407:599

Prof. Peter AgreNovel prize (Chemistry) "for the discovery of water channels" (2003)

Discovery; 1992

Before discovery of aquaporins ？

After all, the message that appeared in textbooks was that water simply diffused "somehow'' across plants membrane and proteins were not involved in these processes.

Biophysicists continued to use pore models to explain membrane permeations without seeking a molecular explanation.

A.R.Schaffner Planta 204:131-139 (1998)

H2O

原形質膜（細胞膜）Plasma-membraene

液胞膜Tonoplast

　　　（ Functional)Cell water permeability ↓Higher than lipid bilayer ↓Water channels suggested

　（ Biochemical ）Abundant protein that function is unknown

　 CHIP28

　 PM28

（ Molecular genetics ）Major Intrinsic Protein (MIP) in eyes

　E.Coli glycerol transporter

（ GlpF)

Aquaporin

Prof. Peter AgreNovel prize (Chemistry) "for the discovery of water channels"

Molecular structure of an aquaporin

Tameshite-Gatten 2007 May, 9

Plant aquaporins

PIP(plasm-membrane…)

　　（原形質膜型）TIP(tonoplast….)

　　（液胞膜型）NIP(Nodulin26-like…)

SIP(small …) ER signaling?

XIP(x …)

Aquaporin = MIP (membrane intrinsic protein)

XIPs are found in some plants (tomato, cotton, moss) but functions are not yet known

35 Major Intrinsic Protein in Arabidopsis 　

13 genes in human, and 1-2 genes in bacteria

Rice aquaporins

0.1

OsNIP2;2

OsNIP3;1

OsNIP3;2

OsNIP3;3

NIPNodulin 26-like Intrinsic Protein

OsPIP2;7

PIP

Plasma membrane Intrinsic Protein

OsTIP3;1

OsTIP3;2

OsTIP4;1

OsTIP4;2

OsTIP4;3

TIPTonoplast Intrinsic Protein

OsSIP1;1

OsSIP2;1

SIPSmall basic Intrinsic Protein

33 genes in rice（ PCP 　 Ishikawa et al. 46 ： 568 (2005) Individual function

RedundancyPhenotype/mutant?

Experimental difficulty

LocalizationStress responseSubstrate

Why many in plants?

H2O2 ［ OsZmPIP2;5, HvPIP2;5 ］ Si(OH)4 /As(OH)4 　

［ OsNIP2;1 ］ B(OH)3 ［ AtNIP5;1 ］

High permeability: maintain cytoplasmTIP aquaporins

Determining cell water permeabilityPIP aquaporins

N

Vacuole(More than 90% volume)

Plasma-mambrane Cell wall

細胞質（ cytoplasm ）

External (soil) w

ater variable

•Wet•Dry•Salt stress

air N2

Peribacteroid membrane

N-fixing bacteria窒素固定菌

N2 　→　 NH3 　 H2O 　　

Legum

inos root cells NOD26（ NIP-type aquaporin ）　　

Relation to N2-fixation, too(Tyerman et al. ）

Aquaporins under osmotic (drought and salt) stresses

H2O

脱水Dehydration

aquaporin

Plasma 　membrane

- 20

0

20

40

60

80

100

120

0 100 200 300 400

NaCl (mM)

Re

lative

gro

wth

(%

)

吸水低下Reduction of water uptake

barley

H2O

Stress ・・・ dehydration

aquaporinPlasmamembrane

• Short term responseInactivation via dephosphorylation and internalization

• Middle term responseSuppression of aquaporin expression → 　 Root water permeability reduction

• Long term reactionOsmotic adjustment to re-establishment of motive forceExpression of aquaporin again

PP

Trafficking/recycling regulation

Chevaliiner et al. PCP 56:819 (2015)

Salt stress ↓H2O2 as signal ↓Trafficking

Internalization of fluorescence after H2O2

Boursiac et al. Plant J. (2008) 56, 207–218

H2O

Salt stress

Transientadaptation

Over-expression

Osmoticadjustment

aquaporinPM

Katsuhara et al.Plant Cell Physiol.(2003)44:1378-1383

over-expression

Low minerals (Carvajal ）aquaporin expression ↓

→ 　 root water permeability ↓

→ 　 shoot growth ↓

Leaf movements (Moshelion ）

Day ： Aquaporin amount/activity ↑

　→　 water influx ↑ 　→　 Leaf open

Night) ： Aquaporin amount/activity↓

　→　 Dehydration 　→　 Leaf close

Many physiological reactions elated to aquaporins

Opening tulip flower (Azad ）　• Low temp→high temp, then opening• Flower cells (lower part) uptake water• PIPs express constantly• TgPIP2;2 activation by phosphorylation under Low

temp→high temp

Fruit enlargement 　（ Shiratake ）

• Initial ・・・ cell division• Middle ～ Later 　 cell elongation by water

uptakeTIPs ・・・ regulation of expressionPIPs ・・・ constant expression regulation via phosphorylation

　　　　

From aquaporin research…

• High quality flowers and fruits

CO2↑

H2O↑

• Drought/salt tolerant crops

• High water usage crops• High CO2 fixing plants

(We are investigation some CO2-permeable aquaporins)