Is the germination stimulant of Orobanche cumana

Transcription

1 Is the germination stimulant of Orobanche cumana A STRIGOLACTONE? Danny Joel, Dina Plakhine, Hamam Ziadna ARO, Israel Swapan Chaudhuri and John Steffens Cornell University, USA

2 Orobanche seeds require a nearby host roots for their germination. Jean-Pierre VAUCHER, pasteur & botaniste ( ) Chemical Stimulus

3 A B C Natural strigolactones strigol D Plant hormones that are secreted by plant roots Xie et al An. Rev. Phytopathol. 48:93 117

4 Several other groups of plant metabolites may also act as germination stimulants

5 Several other groups of plant metabolites may also act as germination stimulants Examples : Peagol Cumarin Ethylene Dihydrosorgoleone Isothiocyanates polyphenols

6 The various plant species release numerous different compounds into the rhizosphere Carbohydrates enzymes amino acids Amides aliphatic acids phenolics, sterols aromatic acids strigolactones etc.

7 Fernández-Aparicio et al., Ann Bot 103: Seeds of the various broomrape species respond differently to crude root exudates of fdifferent plants O. Minor seeds P. aegyptiaca seeds Germin nation legumes cereals GR R24 legumes Flax, cotton omato % Plant origin of root exudates

8 O. cumana seeds specifically respond to sunflower root exudates O. cumana seeds er sunflow cotton cereals GR24 O. minor P. aegyptiaca O. minor seeds P. aegyptiaca seeds legumes cotton cereals GR24 sunflo ower legumes cotton cereals GR24 Fernández-Aparicio et al., Ann Bot 103:

9 O. cumana seeds specifically respond to sunflower root exudates

10 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. cumanagermination Joel et al. (2011) Phytochem. 72:

11 Dehydrocostus Lactone DCL was isolated and identified by Swapan Chaudhuri in John Steffens Lab As part of a BARD projects in

12 HPLC profiles of DCL Root extracts Root Exudates Stimulant Joel et al. (2011) Phytochem. 72:

13 Dehydrocostus Lactone In order to prove that the sunflower germination stimulant for O. cumana is indeed DCL, and not a strigolactone, which may also be released by sunflower roots, Three key aspects have been clarified:

14 1. Does DCLfrom another source stimulate O. cumana germination? Sunflower DCL Costus DCL (sigma) ion % Ger ermination % Germina ation % Germinati A O. cumana P. aegyptiaca Log [M] ation % Germin O. cumana P. aegyptiaca Log [M] Joel et al. (2011) Phytochem. 72:

15 2. Does inhibition of DCL biosynthesis prevent germination stimulation? Control No inhibitor Mevastatin Inhibitor of DCL biosynthesis 1 μ M 10 μ M Fluridone Inhibitor of strigolactone biosynthesis 10 μm 25 μm A D E B C O. cumana seed germination in the sunflower rhizosphere Joel et al. (2011) Phytochem. 72:

16 3. How does phosphate p starvation affect DCL exudation in sunflower? 100 O. cumana - Sunflower 100 P. aegyptiaca - tomato % Germina ation P -P +P -P P -P +P -P Between roots 1-2 cm from roots 0 Between roots 1-2 cm from roots Joel et al. (2011) Phytochem. 72:

17 In short : We have shown that DCL is indeed the specific stimulant for O. cumana Released to the rhizosphere of sunflower plants Product of the mevalonate biosynthetic pathway Not affected by phosphate starvation

18 Different O. cumana populations Differ in their relative germination response Response to dilutions of root exudates crude crude -10 crude -100 GR24 germination Population O. cumana populations These results hint that DCL is not the only germination stimulant of some O. cumana populations Joel et al. (2011) Phytochem. 72:

19 Macías et al J. Agric. Food Chem. 57: synthetic derivatives of dehydrocostus lactone (DCL) can stimulate germination of Orobanche cumana % 2 Germ mination 4 DCL

20 Based on these results we suggest that Similar to the strigolactone family of germination stimulants, a family of sesquiterpene lactones is released to the rhizosphere of the various sunflower cultivars (and possibly also by other plant species), and differentially stimulate the germination of various Orobanche populations Joel et al. (2011) Phytochem. 72:

21 Swapan Chaudhuri and John Steffens Cornell University, USA Dina Plakhine, Hamam Ziadna, Danny Joel ARO, Israel

22 Thank you