A comparison of PTI defense profiles induced in Solanum tuberosum by PAMP and non-PAMP elicitors shows distinct, elicitor-specific responses

Abstract

The induction of general plant defense responses following the perception of external elicitors is now regarded as the first level of the plant immune response. Depending on the involvement or not of these molecules in pathogenicity, this induction of defense is called either Pathogen-Associated Molecular Pattern (PAMP) Triggered Immunity or Pattern Triggered Immunity-both abbreviated to PTI. Because PTI is assumed to be a widespread and stable form of resistance to infection, understanding the mechanisms driving it becomes a major goal for the sustainable management of plant-pathogen interactions. However, the induction of PTI is complex. Our hypotheses are that (i) the recognition by the plant of PAMPs vs non-PAMP elicitors leads to specific defense profiles and (ii) the responses specifically induced by PAMPs target critical life history traits of the pathogen that produced them. We thus analyzed, using a metabolomic approach coupled with transcriptomic and hormonal analyses, the defense profiles induced in potato foliage treated with either a Concentrated Culture Filtrate (CCF) from Phytophthora infestans or two non-PAMP preparations, β-aminobutyric acid (BABA) and an Ulva spp. Extract, used separately. Each elicitor induced specific defense profiles. CCF up-regulated sesquiterpenes but down-regulated sterols and phenols, notably α-chaconine, caffeoyl quinic acid and rutin, which decreased spore production of P. infestans in vitro. CCF thus induces both defense and counterdefense responses. By contrast, the Ulva extract triggered the synthesis of a large-spectrum of antimicrobial compounds through the phenylpropanoid/flavonoid pathways, while BABA targeted the primary metabolism. Hence, PTI can be regarded as a heterogeneous set of general and pathogen-specific responses triggered by the molecular signatures of each elicitor, rather than as a uniform, non-specific and broad-spectrum set of general defense reactions.

Multiple infections influence the resistance of potato cultivars to late blight and potato cyst nematodes

“…infestans develops a strong counter‐defence activity against a wide range of defence pathways. This is consistent with earlier observations (Martin et al, 2020; Thomas et al, 2019) and supports the idea that P . infestans fitness is directly linked to its ability to maintain a biotrophic interaction with its host for as long as possible (Kröner et al, 2019).…”

Gene expression and phytohormone levels in the asymptomatic and symptomatic phases of infection in potato tubers inoculated with Dickeya solani

“…These results suggest reduced production of solanine in infected tuber tissue at the beginning of the infection. A similar reduction in glycoalkaloids was also evident in potato plants induced by Phytophthora infestans elicitors [ 60 ]. It seems that when the tubers allocate resources for phenylpropanoid and flavonoid production, they produce less toxic phytoalkaloids.…”

Arabinogalactan Protein-Like Proteins From Ulva lactuca Activate Immune Responses and Plant Resistance in an Oilseed Crop

“…The ulvan extracted from U. lactuca was used for comparison. It activates plant immunity through the RBOH-dependent JA signaling pathway without inducing hypersensitive response (HR; Jaulneau et al, 2010 ; Freitas and Stadnik, 2015 ; Martin et al, 2020 ).…”

“…Laminarins, β-glucan-containing polysaccharides of brown macroalgae were also reported to exhibit plant-eliciting properties ( Klarzynski et al, 2000 ; Aziz et al, 2003 ). Finally, ulvan polysaccharide, constitutive component of the cell walls of the green macroalgae Ulva genus was also reported to activate PTI ( Cluzet et al, 2004 ; Jaulneau et al, 2010 ; Martin et al, 2020 ; Borba et al, 2021 ).…”