Compounds for activating defense priming in plants

  • Wirkstoffe zur Aktivierung des Abwehr-Primings in Pflanzen

Schillheim, Britta; Conrath, Uwe (Thesis advisor); Slusarenko, Alan (Thesis advisor)

Aachen (2019, 2020)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2019

Abstract

Modern synthetic pesticides provide effective crop protection, but also raise environmental and health concerns. For the realization of an environmental and consumer-friendly plant protection, it is necessary to find effective, natural or near-natural active substances to complement the amounts of partially harmful substances on the cultivated areas and end products. One promising strategy is to use the so-called plant defense priming, which prepares the plant-specific defense mechanisms for improved disease resistance and stress tolerance through pre-treatment with an activating compound. A screening system for compounds that prime the Pep13-induced furanocoumarin secretion in parsley cell cultures to identify novel compounds with priming-inducing activity in plants was optimized for a higher throughput. The screen produced 13 compounds of different chemical groups with priming-inducing activity, thereunder two pyrazole derivatives, the surfactant surfactin (SFT), methionine sulfoximine (MSO), buthionine sulfoximine (BSO), the sulfone-based anti-inflammatory drug Vioxx and four sulfoximine-based Vioxx analogues. Three of the priming-inducing compounds were glucosinolates, respectively isothiocyanates (glucosinolate breakdown products) that are natural compounds contained in cruciferous plants: Glucobrassicin (GBC) and the isothiocyanates sulforaphane (SFN) and benzyl isothiocyanate (BIT). Pretreatment of Arabidopsis thaliana (hereafter Arabidopsis) with SFN enhanced the later activation of the WRKY6 defense gene by the bacterial elicitor flg22 and directly activated PDF1.2. The defense priming induced by SFN was associated with modifications to histones and the formation of open chromatin sites on defense gene promoters of WRKY6 and PDF1.2. Pretreatment with SFN also seems to reduce the susceptibility of Arabidopsis to downy mildew disease (Hyaloperonospora arabidopsidis). Because SFN has antimicrobial activity, it was not possible to distinguish whether the reduction of disease susceptibility against downy mildew is due to defense priming, direct inhibition of the pathogen or a combination of both of these possibilities. SFN is a natural compound contained in human diet. Therefore, it presents a promising candidate for the development of a novel, nonhazardous plant protectant with a dual mode of action.

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