How do plants respond to stress?...
Salt
Anoxia
Heat
Freezing
Drought
4th July / 2008 – Ciência 200
–M. Margarida Oliveira
How do plants respond to stress?...
Cork oak
(Quercus suber)
Tolerance in crop plants
The environmental
influence
Except gravity, all the other
signals vary in intensity,
every minute!
Mature
cells
Growing
cells
Physiological
and
biochemical
responses
Morphological
and
developmental
responses
The growing cells
in plants
Plant development occurs
after embryogenesis
Some plants can tolerate extreme conditions
Salinity
Ice Plant (chorão)
Mesembryanthemum chilense
Atriplex nummularia Salt gland
Mangroves – (Sapais)
high salinity,
unstable substratum,
anaerobic conditions…
Salt
excretion in
Avicennia
Some plants can tolerate extreme conditions
Drought
Growth under
control irrigation
Under
drought
Craterostigma plantagineum
(resurrection plant)
… the plant modifies
its transcriptome!
12h after
re-hydration
How are genes switched on and off ?
DNA encodes genes and contains signals for their control
Transcriptional regulatory networks
Developmental signals
Environmental stimuli
or stress
Induction
Modification
P
A
TF
TF1
1
Ub
B
TF3
TF
TF2
2
C
TF4
P
TF TF TF
II IIF II
HP
E
TFIIB
RNA
pol
II
TFIID
TFIIA
TATA
promoter
Degradation
Basic machinery
Transcription
+1
ATGNNNNN
gene
mRNA
TFs interact with DNA and proteins
Basic--helix
Basic
helix--loop
loop--helix
(bHLH
bHLH))
Interaction with DNA through
2 α-helices and with basic aa.
residues connected by a loop
and typically dimeric
Transcriptional network of abiotic stress response
TFs
Drought, High salinity
Biotic stress
and wounding
Cold
Signal perception
Post-transcriptional
modification
Jasmonic acid
ABA
Modifiers
ABA--independent
ABA
ICE1
ICE
1
HOS1
Sumoylation
SIZ
SIZ1
1
ICE1
ICE
1
MYB
MYC
AREB/ABF
ZF--HD NAC
ZF
?
DREB2
CBF3
CBF
3/DREB
/DREB1
1A
CBF4/DREB1D
DREB2
?
CBF1/DREB1B
ZAT12
CBF2/DREB1C
AREB/ABF
MYCR MYBR
RD22
CAB
ABRE
RD29
RD29B
B
rps--1like NACR
rps
ERD1
STZ/ZAT10
STZ/ZAT
10
DRE/CRT
RD29A
?
?
Photosynthesis related genes?
?
Single genes make a difference
in stress response
Rice growing in Beira
(Mozambique)
Monitoring TF genes involved
in drought stress tolerance
Control
Drought stress recovery
HvCBF4
Abiotic stresses in crop production
Salt, drought , cold,
flooding
heat, ozone, UV-B,
toxic metals…
50
50%
% of crop losses
world wide
Iowa –> 3 billion US
dollars in
crop losses
As much as 80%
of the crop harvest
can be destroyed
“In the next 50 years, mankind will consume as much food as we have
consumed since the beginning of agriculture 10,000 years ago”
Clive James
(President ISAAA - International Service for the Acquisition of Agri-biotech Applications)