Insect eggs induce a systemic acquired résistance in Arabidopsis thaliana


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PhD thesis: a PhD thesis.
Insect eggs induce a systemic acquired résistance in Arabidopsis thaliana
REYMOND Philippe
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Université de Lausanne, Faculté de biologie et médecine
Faculté de biologie et de médecine
Université de Lausanne
CH-1015 Lausanne

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Although they constitute an inert stage of the insect's life, eggs trigger plant defenses that lead to egg mortality or attraction of egg parasitoids. It was recently found that salicylic acid (SA) accumulâtes in response to oviposition by the Large White butterfly Pieris brassicae, both in local and systemic Arabidopsis leaves. In addition, eggs induced a response that is similar to the récognition of pathogen-associated molecular patterns (PAMPs), which are involved in PAMP-triggered immunity (PTI). In this thesis, I demonstrate that natural oviposition by P. brassicae or treatment with egg extract inhibit growth of différent Pseudomonas syringae strains in Arabidopsis thaliana through the activation of a systemic acquired résistance (SAR). This egg-induced SAR involves the metabolic SAR signal pipecolic acid, depends on ALD1 and FMOl, and is accompanied by a priming of defense genes upon secondary infection. Moreover, I found that ICSl-dependent SA accumulation was not required for SAR establishment but that it depends on MPK3 and MPK6 sustained activation. Furthermore, I found that components of the indole metabolism are needed to inhibit pathogen growth in systemic leaves. Additionally, the résistant state is not only efficient against bacteria but has a broad-range spectrum, rendering the plant more résistant against différent pathogens such as the necrotrophic fungus Botrytis cinerea or the oomycete Hyaloperonospora arabidopsidis. Finally, although P. brassicae larvae showed a reduced performance when feeding on P. syringae-infected plants, this effect was less pronounced when infected plants had been previously subjected to oviposition. This unique phenomenon might illustrate a strategy by insect eggs to manipulate plant defenses and prevent the detrimental effect of pathogens on feeding. Larvae. Altogether these findings may open the way for a potential use of egg-extract as priming agent in agronomy.
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07/06/2017 12:49
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20/08/2019 13:23
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