Priming of special metabolism in Arabidopsis thaliana mediates elicitor-induced resistance to fungal infection

Biotic elicitors trigger in plants a robust but transient expression of defense-related genes, followed by a reduced susceptibility to pathogen infection. To investigate the molecular basis of elicitor-induced resistance, we analzyed the transcriptome of Arabidopsis leaves treated with the bacterial elicitor flg22 and inoculated, after 24 h, with the fungal pathogen Botrytis cinerea. In the absence of infection, defense-related genes were not significantly up-regulated 24 h after elicitation, though a transient repression of growth-related genes could be observed. In contrast, flg22-treated plants showed, upon infection, increased expression of genes involved in special metabolism. Genetic analysis confirmed that indolic compounds and aliphatic glucosinolates contribute to flg22-induced resistance. Moreover, elicitation did not affect seed production, suggesting that priming of special metabolism allows increased resistance to pathogens with minimal impact on fitness.