Abstract
Microbe-associated molecular patterns (MAMPs) lead to the activation of the first line of plant defence. Few fungal molecules are universally qualified as MAMPs, and proteins belonging to the cerato-platanin protein (CPP) family seem to possess these features. Cerato-platanin (CP) is the name-giving protein of the CPP family and is produced by Ceratocystis platani, the causal agent of the canker stain disease of plane trees (Platanus spp.). On plane tree leaves, the biological activity of CP has been widely studied. Once applied on the leaf surface, CP acts as an elicitor of defence responses. The molecular mechanism by which CP elicits leaves is still unknown, and the protective effect of CP against virulent pathogens has not been clearly demonstrated. In the present study, we tried to address these questions in the model plant Arabidopsis thaliana. Our results suggest that stomata rapidly sense CP since they responded to the treatment with ROS signalling and stomatal closure, and that CP triggers salicylic acid (SA)- and ethylene (ET)-signalling pathways, but not the jasmonic acid (JA)-signalling pathway, as revealed by the expression pattern of 20 marker genes. Among these, EDS1, PAD4, NPR1, GRX480, WRKY70, ACS6, ERF1a/b, COI1, MYC2, PDF1.2a and the pathogenesis-related (PR) genes 1–5. CP rapidly induced MAPK phosphorylation and induced the biosynthesis of camalexin within 12 hours following treatment. The induction of localised resistance was shown by a reduced susceptibility of the leaves to the infection with Botrytis cinerea and Pseudomonas syringae pv. tomato. These results contribute to elucidate the key steps of the signalling process underlying the resistance induction in plants by CP and point out the central role played by the stomata in this process.
Highlights
Microbe- or pathogen-associated molecular patterns (MAMPs/ PAMPs) are microbe-derived molecules with a key role in the plant immune system: their perception by pattern recognition receptors (PRRs) leads to the activation of PAMP-triggered immunity (PTI), which is the first line of defence against pathogens [1].In fungi, relatively few molecules are universally considered as Microbe-associated molecular patterns (MAMPs), such as chitin, with its variants like chitosan, ethyleneinducing xylanase, b-glucans, necrosis- and ethylene-inducing peptide 1 (Nep1)-like proteins and ergosterol [2,3,4]
As the oxidative burst is one of the first responses occurring in plants after MAMP recognition [2], we assessed the ability of CP to elicit Arabidopsis leaves by analysing the production of hydrogen peroxide
reactive oxygen species (ROS) are central players in the complex signalling network of cells and it is well known that MAMPs cause an oxidative burst upon their recognition by the plant [2]
Summary
Relatively few molecules are universally considered as MAMPs, such as chitin, with its variants like chitosan, ethyleneinducing xylanase, b-glucans, necrosis- and ethylene-inducing peptide 1 (Nep1)-like proteins and ergosterol [2,3,4]. Some of these molecules are produced by fungi, such as b-glucans and Nep1-lke proteins, which can be found in oomycetes and bacteria [5,6]. Cerato-platanin proteins (CPPs) are produced by plant pathogenic and non-pathogenic fungi, both ascomycetes and basidiomycetes [7]. When CPPs are applied on host and non-host plants, they induce defence-related responses and resistance against pathogens [13,14,15,16]
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