Rafaëla Lopez-Martin

Thesis started December 1^st 2016, defended in july, 13^th
Encadrant : Florence Val

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Abstract:

The induction of response defences via the Pathogen-Associated Molecular Pattern (PAMP)-Triggered Immunity provides all plants an arsenal of antimicrobial compounds against pathogens. Stimulation of these defences by exogenous elicitors could be a strategy to reduce the pesticides but this requires a better understanding of the induction mechanisms. This induction could depend on both the origin of the elicitor and the genotype. Two potato genotypes partially resistant to Phytophthora infestans were treated with a PAMPs from P. infestans, the Concentrated Culture Filtrate (CCF), a synthetic molecule, the β-aminobutyric acid (BABA); and an Ulva spp extract. 48h after treatment, the induced metabolites in the leaflets were first compared by a non target metabolomic using a UPLC-qTOF-MS^e, then through targeted metabolomic and transcriptomic approaches. The results showed that (i) each elicitor induced a specific metabolic profile reprogramming: the BABA and the CCF induced the benzylisoquinoline alkaloids and the Ulva extract, the alkaloid sterols and phenylpropanoids; (ii) the transcript analysis partially confirmed these inductions; (iii) the signalling depended on the JA pathway for the Ulva extract while it is rather SA pathway-dependent for the BABA and CCF; (iv) the abundance of several antimicrobial metabolites was genotype-dependent. Our results suggest that the induction of the antimicrobial compounds depends on the elicitor/genotype interaction and on the specific perception of the elicitor. In order to improve their efficiency in the field, special attention should be paid on the defence-related metabolic print generated by each elicitor.

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