Seminar Dr Guillaume Brun
Two weeks to survive: molecular mechanisms harmonizing seed conditioning, germination, and haustoriogenesis in parasitic weeds of the Orobanchaceae family
- Monday, 7 september 2026 11 am, INRAE, Versailles
Specialist plants have turned into fully parasitic weeds that withdraw water, nutrients, and macromolecules from crops via a specialized feeding structure, the haustorium, thereby causing tremendous yield losses. Parasitism brought about numerous molecular and functional adaptations for seed and seedling development in obligate parasitic species of the Orobanchaceae family. Seeds must undergo a conditioning period, after which germination requires host-derived compounds like strigolactones. Then, seedlings develop a haustorium upon perception of host-derived haustorium-inducing factors (HIFs), guiding the parasite to a host within a few days before it exhausts its resources. Outstanding spatiotemporal precision is required for this developmental sequence, yet its molecular foundations remain elusive.
Here, integrating seed transcriptome data for 13 Orobanchaceae species of varying host-dependency for germination using a stationary Ornstein-Uhlenbeck model highlighted gene sets with low expression conservation that discriminate species according to their host requirements. Additionally, we combined time-series transcriptomics with targeted gene and hormone quantitation of parasite seeds during host-induced germination. We identified that the limited transcriptional variations in the early stages of germination stimulant response modulate abscisic acid (ABA) and gibberellins synthesis and signaling. We found that an early decrease in ABA levels controls downstream signaling, with a predominant role for histone deacetylation and a significant reduction in bioactive cytokinins. Finally, we demonstrated that contrary to the current paradigm, haustorium development is naturally host-independent in parasitic weeds, as seedlings use their own HIFs in a dose-dependent manner. HPLC-MS time-series analysis highlighted increases in bioactive cytokinins as the seedlings develop. We also demonstrated that new classes of HIFs, including phytosterols, quinones, and flavonoids act synergistically at hormonal concentrations. These findings coupled with transcriptomics suggests that lignin neosynthesis during conditoning is a template for producing bioactive HIFs through post-germinative oxidative stress.
Our research elucidates the key molecular processes occurring during the critical first two weeks from conditioning to haustorium development, prompting for a re-evaluation of our understanding of allelopathic communication between parasitic Orobanchaceae and their hosts.
Dr. Guillaume Brun," Biological Sciences and Biotechnology" US2B, Nantes Université, Nantes
Invitation: Sandrine Bonhomme, "Strigolactones and Allelochemicals Signaling" SAS team
Seminar in connection with the research developed at the Institute Jean-Pierre Bourgin for Plant Sciences.
Here, integrating seed transcriptome data for 13 Orobanchaceae species of varying host-dependency for germination using a stationary Ornstein-Uhlenbeck model highlighted gene sets with low expression conservation that discriminate species according to their host requirements. Additionally, we combined time-series transcriptomics with targeted gene and hormone quantitation of parasite seeds during host-induced germination. We identified that the limited transcriptional variations in the early stages of germination stimulant response modulate abscisic acid (ABA) and gibberellins synthesis and signaling. We found that an early decrease in ABA levels controls downstream signaling, with a predominant role for histone deacetylation and a significant reduction in bioactive cytokinins. Finally, we demonstrated that contrary to the current paradigm, haustorium development is naturally host-independent in parasitic weeds, as seedlings use their own HIFs in a dose-dependent manner. HPLC-MS time-series analysis highlighted increases in bioactive cytokinins as the seedlings develop. We also demonstrated that new classes of HIFs, including phytosterols, quinones, and flavonoids act synergistically at hormonal concentrations. These findings coupled with transcriptomics suggests that lignin neosynthesis during conditoning is a template for producing bioactive HIFs through post-germinative oxidative stress.
Our research elucidates the key molecular processes occurring during the critical first two weeks from conditioning to haustorium development, prompting for a re-evaluation of our understanding of allelopathic communication between parasitic Orobanchaceae and their hosts.
Dr. Guillaume Brun," Biological Sciences and Biotechnology" US2B, Nantes Université, Nantes
Invitation: Sandrine Bonhomme, "Strigolactones and Allelochemicals Signaling" SAS team
Seminar in connection with the research developed at the Institute Jean-Pierre Bourgin for Plant Sciences.
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