Regulation of grape bud dormancy release
Dr. Etti Or
Volcani center
Agr iculture Research Organization
Israel
The Bud Dormancy team
Ethylene induced macromolecule catabolism – the switch required for bud meristem growth resumption?
0
20
40
60
80
100
120
7 14 18 21 24 27 32 35
Control-6.11HS-6.11HC-3%-6.11HC-4%-6.11HC-5%-6.11
Chemical and physical stress agents induce bud dormancy release
hydrogen cyanamide (HC) and Heat Shock (HS)
Azid (AZ) Hypoxia
Pang et al., 2007, JExBotHalali et al., 2008, PlantaOphir et al.,2009, PMB
Our initial model for the molecular cascade that activate dormancy release (based on years of comparative analyses
of response to dormancy release stimuli…)Here we bring on the tip of the fork support for the model and suggest that Ethylene induced catabolism may be a central switch of dormancy release
C
CC
020
4060
80100
120140
160
3 6 12 24 48
Time from treatment
Con
cent
ratio
n (p
pm)
C
HC
HSEthanol
020406080
100
7d 11d
14d
18d
21d
25d
28d
Bud
s br
eak
(%)
Days after treatment
ControlNitrogen
Anaerobiosis induce bud dormancy release
Azid, HC and HS temporarily induce anaerobic respiration, to face energy shortage caused by impaired aerobic respiration
0
2000
4000
6000
8000
10000
12000
Nor
mal
ized
Rea
ds
Alcohol DHL
05000
100001500020000250003000035000
Nor
mal
ized
Rea
ds
Pyruvate DecarboxylaseH
0
20
40
60
80
100
120
ם עי
פקת
יצפר
%)
(
2011-12A
Dormancy cycle
AzidControl
Ethanol
Ophir et al.,2009, PMBOr, unpublished
Temporary induction of fermentation also occure under vineyard conditions during deep dormancy, indicative of an energy crisis.
0500
100015002000250030003500400045005000550060006500
Met
abol
ite/R
ibito
l(IS)
Peak
Are
a Ra
tio
Sucrose
Sucrose Degradation Sucrose synthesis
• Sucrose degradation is activated during deep dormancy• It is probably induced in response to enhanced Glycolysis needed to supply
pyruvate for anaerobic respiration• Sucrose degradation decrease during dormancy release in parallel with
increased sucrose synthesis capacity and sucrose level• Similar regulation appears in response to HC and additional stimuli (not shown)
0
5000
10000
15000
20000
25000N
orm
aliz
ed R
eads
Pyruvate kinaseG
Glycolysis
0200400600800
1000120014001600
Nor
mal
ized
Rea
ds
Hexokinase2D
• HC and AZ upregulate Ethylene synthesis by temporary induction of ethylene synthesis genes (ACS, ACO)
• Ethylene induce dormancy release
• Temporary increase in ethylene biosynthesis capacity is also regulated at the transcription level during the natural dormancy cycle
• Inhibition of ethylene signaling inhibit bud break and the effect is timing dependent
Shi et al, 2018, submitted
VvACO VvACOEthylene biosynthesis
Ethylene signalingWe formerly identified ERF genes, which are known sensors of energy crisis and activate hypoxic response• As expected, they accumulates in response to hypoxia• Less expected, they directly respond to HC induced signal• They are positively regulated during deep dormancy in transcript or protein level
Ophir et al.,2009, PMBShi et al, in preparation
RNAseq of AZ, HC, Ethylene, hypoxia and NBDHC treated buds
Down regulated (22) Up regulated (11)
We identified all the ERFs, as well as other genes that are regulated by HC, Azid, hypoxia AND ethylene….assuming that they are primary regulators of the cascade
ABA delay bud break and reduce the enhancing effect of HC, HS, Azid and hypoxia on dormancy release.
020406080
100
HC Control ABA-HC ABA
Buds
bre
ak (%
)
020406080
100
HS Control ABA-HS ABA
7 11 14 18 21 25 28
020406080
100
AZ Control ABA-AZ ABA
7 11 14 18 21 25 28
020406080
100
Hypoxia Control ABA-Hypoxia ABA
A B
C D
Days after treatmentRecovery from the inhibition was demonstrated in the combined ABA-HC treatment whereas no recovery was evident in the ABA-treated, compared to the control.
Zheng et al., 2015, JExBot
HC lead to reduction of ABA levels and increase of level of ABA
degradation products in the buds
Down-regulation of VvNCED1 andup-regulation of VvA8H-CYP707A4levels by HC may be responsibletogether for decreased ABA leveland increased ABA catabolites levelin response to HC.
Natural dormancy cycle
Zheng et al., 2015, JExBotZheng et al., 2018, PCE
The OE VvA8H-CYP707A4 grapevine lines presented significantly improved rate and level of dormancy release
cuttings test
All vine test
Zheng et al., 2018, PCE
Profiling the expression of GA metabolism throughout the natural dormancy cycle suggests during endodormancy release:
• levels of active GA biosynthetic enzymes increased
• levels of active GA degradation enzyme decreased
These results are in agreement with the initial model
However… In reality, things appears to be more complicated…
Zheng et al., 2018, JExBot
During initial steps of meristem activation, GA has a strong inhibiting effect. Once meriatem is activated, GA has an enhancing effect, probably on primordia growth
Regulation of grape bud dormancy release
Dr. Etti Or
Volcani center
Agr iculture Research Organization
Israel
Thank you and thanks to…
The Bud Dormancy team
Top Related