Improving the crops water use
efficiency: From Ecophysiology to
Biotechnology and backwards
Medrano H.; Pou A.; Tomàs M.; Martorell
S.; Escalona, JM.;Gulias, J.; and Flexas J.
Research Group on
‘PLANT BIOLOGY UNDER MEDITERRANEAN CONDITIONS’
Universitat de les Illes Balears - IMEDEA
Palma de Mallorca, SPAIN
BUT, the increase in crop production is clearly linked to the
increase of irrigated cropping areas
Water scarcity:
First limiting factor of crop yield
High water demand crops + wide (and increasing ) crop
extension under irrigation
High water volume needed for irrigation: ( >70%
Human Available Water
THE SUSTAINABILITY OF AGRICULTURE
(FOOD PRODUCTION) DEPENDS ON
THE IMPROVEMENT OF WATER USE
EFFICIENCY
Climatic Change:
Global warming => Higher ETP (because higher T)
+Lower rain ?
+Higher unpredictability of rainfall episodes
Thus crop production will be even more
dependent on irrigation
Winter
Summer
IPCC Report 2007
Moreover, THE WATER FOOTPRINT ISSUE
It’s gaining importance as subject for food sustainability information
Green + blue + grey water volumes for a food unit
On average,
producing one tomato (assuming it
to be equal to 100g) evaporates
1.4 liters of green water
6.1 liters of blue water
0.7 liters of grey water
totalling 8.2 litres per tomato
(Chapagain and Orr, 2008). ).
Apple: Global average water
footprint: 70 liters for one apple.
We assume here a hundred-grams
apple. One glass of apple juice
(200 ml) costs about 190 liters of
water. UK Institute for Food and Dood
Research. US Apple Association
http://www.waterfootprint.org/?page=files/productgallery&products
IMPROVING WUE, A MANDATORY OF THE
UNITED NATIONS ORGANIZATION
More production
with less water
(‘more crop per drop’)
INCREASING PRESENCE OF THIS SUBJECT IN
THE SCIENTIFIC LITERATURE
Search: Water AND use AND efficiency
Number of papers
8000
6000
4000
2000
20
12
20
10
-
20
10
20
05
-
20
05
20
00
-
20
00
19
95
-
19
95
19
90
-
19
90
80
-
19
19
00
-
19
80
0
Time span
Source: ISI Web of Knowledge; Web of Science (13th September 2012
FROM ECOPHYSIOLOGY
Two main ways to improve WUE
Photosynthesis
3
Maximizing crop
photosynthesis
Genetic
improvement Biotechnology
1
2
Reducing gs
(water consume)
-Soil and crop
management
-Regulated deficit
irrigation (RDI)
Stomatal conductance
… BUT, HOW TO ACHIEVE THEM?
THE CO2 FLUX FROM ATMOSPHERE TO CARBOXYLATION SITE
RUBISCO
MESOPHYLL
CONDUCTANCE
STOMATAL
CONDUCTANCE
CO2
H2O
gm shows important differences between and within species
and groups
Increasing crops WUE through increases in the mesophyll conductance
WHICH FACTORS DO INFLUENCE THE MESOPHYLL CONDUCTANCE?
MORPHOLOGICAL FACTORS
0,5
EVERGREENS PRESENT LOWER
MESOPHYLL CONDUCTANCES TO CO2
0,4
?
-2
-1
gm (mol CO2 m s )
0,4
0,3
0,2
0,3
0,2
evergreens
Evergreens
0,0
deciduous
Deciduous
0,0
semi-deciduous
Semi-deciduous
0,1
herbaceous
Wild
herbs
0,1
crops
Crop herbs
gm (mol CO2 m-2 s-1)
0,5
LMA SETS THE MAXIMUM
LIMITS OF gm
0
100
200
300
400
500
LMA (g m-2)
LMA = THICKNESS x DENSITY
Flexas et al. (2008) Plant Cell Environ. 31, 602-622
Literature survey of 84 species under non-stressing conditions
600
IN WHAT WAY, gm is related with WUE?
AN = gs (Ca – Ci) = gm (Ci – Cc)
AN can be increased by increasing gs, gm or both
But increasing gs would result in decreased AN / gs, i.e., decreased
intrinsic water-use-efficiency (WUE)
AN / gs = gm / gs (Ci – Cc)
Therefore increasing gm / gs should favour
increased AN / gs, i.e., increased WUE)
MESOPHYLL conductance shows important variations
among grapevine cvars both under irrigation and
water stress
0,25
gm (mol CO2 m-2 s-1)
Irrigated
Drought
0,20
0,15
0,10
0,05
llo
Te
m
pr
an
i
Sy
ra
h
re
na
ch
e
M
al
va
M
si
an
a
to
N
eg
ro
R
ic
ht
er
11
0
C
al
le
t
G
C
ab
e
rn
et
S.
0,00
CULTIVAR
and some cvars are less affected by water stress
Tomas et al., 2012
and Effectivelly, higher gm/gs corresponds
……………………………………..to higher WUE
AN/gs (µmol CO2 mol H2O-1)
140
CBS
GS
TS
MS
RS
CBR
GR
TR
MR
RR
120
100
80
r ²=0.90
60
40
0.0
0.5
1.0
1.5
gm/gs
2.0
2.5
3.0
Thomas et al. 2012
AS HAS BEEN ALSO SHOWN IN TOMATO (TR)
Increasing crops WUE through increases in the mesophyll conductance
160
R2 = 0.762
140
-1
AN/gs (mol CO2 mol H2O)
7 Balearic local genotypes of tomato + 1 commercial variety
2 water treatments
120
100
80
60
40
0,0
0,5
1,0
1,5
2,0
2,5
3,0
gm/gs
Drought
gm/gs
gm/gs as a useful breeding target
to improve WUE
Galmés et al. (2011) Plant Cell Environ 34, 245-260
-TO BIOTECHNOLOGY
IMPROVING WUE BY BIOTECHNOLOGY WAYS
METABOLIC CANDIDATES FOR RAPID CHANGES IN gm
- Carbonic anhydrase (Gillon and Yakir 2000 Plant Physiol. 123, 201-213)
- Aquaporins (Flexas et al. 2006 Plant J. 48, 427-439)
- Others (Flexas et al. 2008 Plant Cell Environ. 31, 602-622)
-TO BIOTECHNOLOGY
IMPROVING WUE BY BIOTECHNOLOGY WAYS
Improving CO2 diffussion inside the leaf
AQUAPORINS
OVERCOMING LEAF CO2 DIFFUSION LIMITATIONS
Increasing crops WUE through increases in the mesophyll conductance
PLASMA MEMBRANE INTRINSIC PROTEINS - AQUAPORINS
AS
W
T
OX
PIP1 TRANSFORMED TOBACCO PLANTS
Western blot of PIP1 expression
TRANSFORMING FOR OVEREXPRESSION OF AQUAPORINS ….
A TARGET TO IMPROVE WUE
GENOTYPE
gm (mol CO2 m-2 s-1)
AN (mmol CO2 m-2 s-1)
WT
0.322  0.020 b
18.5  0.6 b
AS
0.176  0.012 a
17.2  0.9 a
OX
0.401  0.045 c
21.9  0.8 c
Flexas et al. (2006) Plant J 48, 427-439
Overexpression of AQPs in
TOMATO, …… Results in
increases the plant production
…….and the leaf WUE
WUE (An/E)
CONTROL
Higher AQP
Control exp
4,3
4,9
+(50mMNaCl)
6,3
8,2
Sade et al. 2010. Plant Physiol.
-TO BIOTECHNOLOGY
IMPROVING WUE BY BIOTECHNOLOGY WAYS
Improving CO2 assimilation:
RUBISCO SPECIFICITY FACTOR
Rubisco specificity factor: the CO2
capture
CO2
CARBOXYLATION
OXYGENATION
vc
[CO2 ]

vo
[O2 ]
O2
c
kcat
Kc
 o
kcat
Ko
PRODUCTIVITY
Crepis triasii
Digitalis minor var minor
Digitalis minor var palauii
Helleborus foetidus
Paeonia cambessedesii
Pistacia lentiscus
Hypericum balearicum
Kundmannia sicula
Pimpinella bicknelli
Beta maritima
Beta vulgaris subsp marcosii
Urtica membranacea
Urtica atrovirens subsp bianorii
Cistus albidus
Phlomis italica
Rhamnus alaternus
Rhamnus ludovici-salvatoris
Limonium virgatum
Limonium gibertii
Limonium magallufianum
Mentha aquatica
Lysimachia minoricensis
Lavatera maritima
Diplotaxis ibicensis
Normalized Rubisco tat 25ºC
Rubisco specificity factor (t
)
1. There is genetic variability in tamong species of arid habitats
2. L. gibertii presents the highest value of tever found in
higher plants
115.000
110.000
105.000
100.000
95.000
90.000
85.000
Galmés et al. (2005) Plant Cell Environ. 28, 571-779
OVERCOMING RUBISCO LIMITATIONS
Nicotiana tabacum
250
200
Red algae
SC/O
150
Diatom
100
Limonium gibertii
Higher plant
Fern
50
Triticum aestivum
Cyanobacteria
Green algae
Proteobacteria
0
0
2
4
6
c
-1
kcat (s )
8
10
Galmés et al. (unpublished)
L. gibertii rubisco: simulation in transformed tobacco and wheat
Different tcould be due to changes
in:
Kc
Vc
Ko
Vo
Potential photosynthesis increase (%)
Tobacco
Wheat
26
11
Cc = 7 mM, Oc = 265 mM
30
12
16
6
5
2
L. gibertii rubisco: simulation in transformed tobacco and wheat
BUT…. under
drought
Different tcould be due to changes
in:
Kc
Vc
Ko
Vo
Potential photosynthesis increase (%)
Tobacco
Wheat
187
45
190
45
Cc = 1.7 mM, Oc = 265 mM
181
38
135
32
Modeling after Farquhar et al. (1980)
Vc,max for Vitis (Schultz, 2003, Funct. Plant Biol. 30, 673-687)
Rubisco Engineering
AN (mol CO2 m-2 s-1)
20
Current Vitis
Limonium , Vc,max 80
15
10
5
0
0.00
0.05
0.10
0.15
-2
0.20
0.25
-1
gs (mmol CO2 m s )
Using gs, Cc and Temperature data from Flexas et al. (2002) Funct. Plant Biol. 29, 461-471
Vc,max for Vitis (Flexas et al., 2006, Physiol. Plantarum. 127,
343-352)
Rubisco Engineering
AN (mol CO2 m-2 s-1)
30
25
Current Vitis
Limonium , Vc,max 80
Limonium , Vc,max 100
20
15
10
5
0
0.00
0.05
0.10
0.15
-2
0.20
0.25
-1
gs (mmol CO2 m s )
Using gs, Cc and Temperature data from Flexas et al. (2002) Funct. Plant Biol. 29, 461-471
Vc,max for Limonium gibertii (Galmés et al., unpublished)
Rubisco Engineering
AN (mol CO2 m-2 s-1)
35
30
25
Current Vitis
Limonium , Vc,max 80
Limonium , Vc,max 100
Limonium , Vc,max 120
20
15
10
5
0
0.00
0.05
0.10
0.15
-2
0.20
0.25
-1
gs (mmol CO2 m s )
Using gs, Cc and Temperature data from Flexas et al. (2002) Funct. Plant Biol. 29, 461-471
Replacing Vitis by Limonium Rubisco could
seriously increase the WUE more under water stress
AN / gs (mol CO2 mol-1 H2O)
Rubisco Engineering
300
Current Vitis
Limonium , Vc,max 80
250
Limonium , Vc,max 100
Limonium , Vc,max 120
200
150
100
50
0
0.00
0.05
0.10
0.15
-2
0.20
0.25
-1
gs (mmol CO2 m s )
If this was combined with higher aquaporine
expression, higher WUE could be expected
Does the higher specificity factor in
Limonium lead to increased WUE?
-1
AN/gs (mol CO2 mol H2O)
110
100
b
c
90
80
b
b
a
70
60
WES
WESS
HE
SDS
d
a
a
b
a
a
a
50
a a
a a
40
< 30%
30-60%
60-90%
> 90%
gs range (% with respect to species maximum)
Medrano et al. 2009
103
10-3
m
mm
10-6
10-9
10-12
mm
Gene
Dimension (m)
1
km
Hour
Gene expression
10-6
10-3
1
103
Time (s)
Week
Year Century
106
109
1012
CONCLUSIONS
-THE IMPROVEMENT OF WUE IS AN UNAVOIDABLE OBJECTIVE FOR
FARMERS AND RESEARCHERS
-ECOPHYSIOLOGICAL STUDIES OF PLANT WATER ECONOMY SHOWS
INTERESTING WAYS TO EXPLORE FOR FUTHER WUE
IMPROVEMENTS
-BIOTECHNOLOGY OFFERS AN EXCITIONG WAY TO IMPROVE THE
PLANT WUE ONCE SPECIFIC TARGETS FOR TRANSFORMATION ARE
INDENTIFIED
-AQUAPORINS AND SPECIFIC FACTOR OF RUBISCO ARE TWO
INTERESTING TARGETS TO BE EXPLORED IN NEAR FUTURE
Cheers!!
Spanish Ministry of Science
Research Group on
‘PLANT BIOLOGY UNDER MEDITERRANEAN CONDITIONS’
Universitat de les Illes Balears - IMEDEA
Palma de Mallorca, SPAIN