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The necrotrophic fungus Botrytis cinerea (B. cinerea) is one of the most aggressive and widespread pathogenic fungi, causing the gray mold disease in over 200 different plants species and severely impacting the quality of harvested fruits. Due to B. cinerea resistance to common synthetic fungicides and their ecological impact, there is a large demand for novel control approaches, such as bio-fungicides. The family of carotenoid-cleavage products, i.e. apocarotenoids, includes important compounds, such as hormones, signaling molecules and growth regulators. Previous studies indicated that the apocarotenoid B-ionone inhibits the growth of some fungal species. In this thesis, we unravel a novel role for B-ionone as a plant regulatory metabolite increasing the resistance against B. cinerea in several plant models. We achieved this by combining phenotypic, transcriptomic, and metabolomic analysis. We show that pretreatment of Arabidopsis plants with B-ionone significantly alleviated the symptoms of B. cinerea infection, modulated hormone homeostasis and affected the interactions between jasmonic acid (JA)/ethylene (ET) and abscisic acid (ABA) hormone signaling pathways β-ionone treatment stimulated JA/ET signaling pathways and repressed the synthesis of ABA upon B. cinerea infection, which reduced the susceptibility of Arabidopsis plants to B. cinerea. To get an overview on the effect of β-ionone on plants at transcript level, we performed an RNA-seq experiment that supported our hypothesis that B-ionone primes and enhances the Arabidopsis immune response to B. cinerea infection and raveled the effect of this volatile on the expression of several transcription factors involved in Arabidopsis immune response to B. cinerea and on transcripts related to cell wall biosynthesis, Map Kinase 3 signaling and hypoxia tolerance. Further experiments performed with transgenic tobacco and tomato plants confirmed the positive role of β-ionone in reducing the symptoms of B. cinerea in green tissues as well as in tomato fruits. The discovery of β-ionone as a new apocarotenoid signaling molecule that regulates plant hormone homeostasis opens up new possibility to control B. cinerea infection and to establish this natural volatile as an environmentally friendly and safe bio-fungicide. |
