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?

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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

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Anaerobiosis induce bud dormancy release

Azid, HC and HS temporarily induce anaerobic respiration, to face energy shortage caused by impaired aerobic respiration

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Ophir et al.,2009, PMBOr, unpublished

Temporary induction of fermentation also occure under vineyard conditions during deep dormancy, indicative of an energy crisis.

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• 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)

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• 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.

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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