Is the germination stimulant

of Orobanche cumana

?A STRIGOLACTONE ?

ARO Israel

Danny Joel, Dina Plakhine, Hamam Ziadna

Swapan Chaudhuri and John SteffensCornell University, USA

ARO, Israel

y,

Orobanche seeds

require a nearby

host roots

for their germination.

Jean-Pierre VAUCHER, pasteur & botaniste (1763-1841)

Chemical Stimulus

Natural strigolactonesA BC Natural strigolactones

Dstrigol

Plant hormones that are secreted by plant roots

Xie et al. 2010. An. Rev. Phytopathol. 48:93–117

Several other groups of plant metabolites

may also act as germination stimulantsmay also act as germination stimulants

Several other groups of plant metabolites

may also act as germination stimulants

Examples :

may also act as germination stimulants

Peagol CumarinEthylene

Examples :

EthyleneDihydrosorgoleone

Isothiocyanates polyphenols p yp

The various plant species release numerous different compounds

into the rhizosphere

CarbohydratesCarbohydrates

enzymes

amino acids

Amides

aliphatic acids

phenolics, sterols

aromatic acids

strigolactones

etc.

Fernández Aparicio et al 2009 Ann Bot 103: 423 431Fernández-Aparicio et al., 2009. Ann Bot 103: 423-431

Seeds of the various broomrape species d diff tl t d t d t f diff t l trespond differently to crude root exudates of different plants

P ti dO. Minor seeds P. aegyptiaca seeds

R24 nna

tion

cereals

omat

o

legumes

GR

Flax

, cot

ton

Ger

min legumes to

%

Plant origin of root exudates

O. cumana seeds specifically respond to sunflower root exudatesspecifically respond to sunflower root exudates

er

O. cumana seeds

sunf

low cereals

cotto

n

GR

24

O. minor P. aegyptiaca

owerO. minor seeds P. aegyptiaca seeds

cereals

cotto

n

GR

24

cotto

n

cereals

legumes

sunf

lo

legumesG

R24

Fernández-Aparicio et al 2009 Ann Bot 103: 423-431Fernández-Aparicio et al., 2009. Ann Bot 103: 423-431.

O. cumana seeds specifically respond to sunflower root exudatesspecifically respond to sunflower root exudates

We hav shown that the sesquiterpene lactone

Dehydrocostus Lactone (DCL)

DCL

Which is structurally differs from the strigolactones

is released to the rhizosphere of sunflower plants

and significantly stimulates O cumana germinationand significantly stimulates O. cumana germination

Joel et al. (2011) Phytochem. 72:624–634

Dehydrocostus Lactone y

DCL was isolated and identifiedby Swapan Chaudhuriin John Steffens’ Lab

As part of a BARD projects in 1992-95

HPLC profiles of DCL

Root extractsRoot extracts

R t E d tRoot Exudates

StimulantStimulant

Joel et al. (2011) Phytochem. 72:624–634

Dehydrocostus Lactone

In order to prove that

the sunflower germination stimulant for O. cumana

is indeed DCL and not a strigolactoneis indeed DCL, and not a strigolactone,

which may also be released by sunflower roots,

Three key aspects have been clarified:

1. Does DCLfrom another source stimulate O. cumana germination ?

Sunflower DCL Costus DCL (sigma)60

erm

inat

ion A

rmin

atio

n

O. cumanaO. cumana

atio

n

60

80

atio

n

40

60

% G

eio

n%

Ger

P aegyptiaca Ger

min

40

60

Ger

min

a

20

% G

erm

inat

i P. aegyptiacaP. aegyptiaca%

G

20

% G

0

%

Log [M] Log [M]-- 99 -- 88 -- 77 -- 66

Joel et al. (2011) Phytochem. 72:624–634

2. Does inhibition of DCL biosynthesis prevent germination stimulation ?

Control

No inhibitor

MevastatinInhibitor of DCL

biosynthesis

FluridoneInhibitor of strigolactone

biosynthesis

10 μM 25 μM1 μ M 10 μ M

BB CCDD EEAA

O. cumana seed germination in the sunflower rhizosphere Joel et al. (2011) Phytochem. 72:624–634

3.How does phosphate starvation p p

affect DCL exudation in sunflower?

O. cumana - Sunflower100

P. aegyptiaca - tomato100

80

100

atio

n

60

80

100

40

60

-P+P -P+P

% G

erm

ina 60

-P+P -P+P40

0

20

Between 1 2 cm

%

0Between 1-2 cm

20

Between roots

1-2 cm from roots

Between roots

1-2 cm from roots

Joel et al. (2011) Phytochem. 72:624–634

In short :

We have shown that DCL is indeed the specific stimulantfor O. cumana

Released to the rhizosphere of sunflower plants

for O. cumana

Released to the rhizosphere of sunflower plants

Product of the mevalonate biosynthetic pathwayy p y

Not affected by phosphate starvation

Different O. cumana populations Differ in their relative germination responseg p

Response to dilutions of root exudates

crudecrude-10crude-10

crude-100

GR24 germination

PopulationO. cumana populations

These results hint that DCL is not the only germination stimulantThese results hint that DCL is not the only germination stimulantThese results hint that DCL is not the only germination stimulantThese results hint that DCL is not the only germination stimulantof some of some O. cumana O. cumana populations populations

Joel et al. (2011) Phytochem. 72:624–634

Macías et al.. 2009. J. Agric. Food Chem. 57:5853-5864

synthetic derivatives of dehydrocostus lactone (DCL) can stimulate germination of Orobanche cumana

%

2

min

atio

n

4

Ger

m

DCL

6-81

13-146-8

Based on these results

we suggest thatwe suggest that

Similar to the strigolactone family of germination stimulantsSimilar to the strigolactone family of germination stimulants,

aa family of sesquiterpene lactonesfamily of sesquiterpene lactonesaa family of sesquiterpene lactonesfamily of sesquiterpene lactones

is is released to the rhizosphere released to the rhizosphere pp

of the various sunflower cultivars (and possibly also by other plant species),

and differentially stimulate the germination of various Orobanche populationsand differentially stimulate the germination of various Orobanche populations

Joel et al. (2011) Phytochem. 72:624–634

Swapan Chaudhuri and John SteffensCornell University, USA

ARO, Israel

Dina Plakhine, Hamam Ziadna, Danny Joel

Thank youThank you