An extract of Penicillium chrysogenum elicits early defense-related responses and induces resistance in Arabidopsis thaliana independently of known signalling pathways

Summary in the original language of the document

An aqueous extract of the mycelium of Penicillium chrysogenum (further called ‘Pen’ induced early defense-related responses such as an extracellular alkalinisation in cell cultures and ethylene production in leaf slices of numerous mono- and dicotyledon plant species, including Arabidopsis thaliana, tomato, tobacco and rice. The Pen-elicitor was sensitive to protease digestion but insensitive to other enzymes, suggesting that the elicitor-active region is a protein or a peptide. Reversed phase, ion exchange and size exclusion chromatography revealed that the Penelicitor is heterogeneous. This prevented further identification of the elicitor. Pen protected A. thaliana from a broad range of pathogens, including an oomycete (Hyaloperonospora parasitica), two ascomycetes (Botrytis cinerea, Alternaria brassicicola) and a bacterium (Pseudomonas syringae pv. tomato DC3000) without having a direct antimicrobial effect. Various mutants of A. thaliana were used to test whether Pen induces resistance on one of the known signaling pathways: Pen was fully protective against B. cinerea in A. thaliana transgenes or mutants impaired in the salicylic acid (NahG, npr1), jasmonic acid (coi1-1), and ethylene (ein2-1) signalling pathway. Similarly, Pen-mediated resistance against H. parasitica was not affected in the mutants npr1, coi1-1 or ein2-1. However, its efficacy was reduced in the transgene NahG. From these data on cell cultures and on A. thaliana we conclude that Pen contains at least one unidentified elicitor, most likely a protein or a glycoprotein, inducing resistance via signal transduction pathways different from classical SA/NPR1- or JA/ethylene-dependent pathways.
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