Haustorium initiation in the obligate parasitic plant Phelipanche ramosa involves a host-exudated cytokinin signal
Résumé
The heterotrophic lifestyle of parasitic plants relies on the development of the haustorium, a specific infectious organ
required for attachment to host roots. While haustorium development is initiated upon chemodetection of host-derived
molecules in hemiparasitic plants, the induction of haustorium formation remains largely unknown in holoparasitic
species such as Phelipanche ramosa. This work demonstrates that the root exudates of the host plant Brassica napus
contain allelochemicals displaying haustorium-inducing activity on P. ramosa germinating seeds, which increases
the parasite aggressiveness. A de novo assembled transcriptome and microarray approach with P. ramosa during
early haustorium formation upon treatment with B. napus root exudates allowed the identification of differentially
expressed genes involved in hormone signaling. Bioassays using exogenous cytokinins and the specific cytokinin
receptor inhibitor PI-55 showed that cytokinins induced haustorium formation and increased parasite aggressiveness.
Root exudates triggered the expression of cytokinin-responsive genes during early haustorium development
in germinated seeds, and bio-guided UPLC-ESI(+)-/MS/MS analysis showed that these exudates contain a cytokinin
with dihydrozeatin characteristics. These results suggest that cytokinins constitutively exudated from host roots play
a major role in haustorium formation and aggressiveness in P. ramosa.
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Licence : CC BY - Paternité
Licence : CC BY - Paternité