The impact of isoprene emission on plant phenotype and on belowground communication with other plants and microorganisms

This thesis explores the possible role of isoprene emission by plants on belowground biology. So far, studies focused their attention on the effects of isoprene at aboveground level. In particular, the experimental part of this thesis goes through several approaches (using metabolomics, transcriptomics, phenomics and metagenomics) to analyze isoprene effects on (1) root physiology, and salt stress tolerance in Arabidopsis thaliana; (2) phenotypic changes in isopreneemitting (IE) and non-emitting (NE) Nicotiana tabacum plants grown in different (non-mixed) and in the same (mixed) pots, and (3) shows preliminary results about the effect of isoprene on fungal and microbial communities. The thesis is made by four chapter and an appendix. In the first chapter, isoprene biosynthesis by plants and its putative protective, priming and hormone-like activity are the presented topics. The current knowledge about the role of plant volatiles (BVOCs) in belowground interactions is also reported. The second chapter reviews the impact of climate change and air and soil pollution on isoprene emission, further highlighting possible impacts and responses in the belowground. In chapter III and IV, the experimental results suggesting that isoprene has a possible role in root physiology are shown, using IE and NE Arabidopsis thaliana (Chapter III) or Nicotiana tabacum (Chapter IV) plants. Furthermore, Chapter IV shows preliminary results on the effect of isoprene on the microbiome in root, rhizosphere, and bulk soil samples of isoprene-emitting and nonemitting plants. At the end, Appendix 1 describes an attempt to generate a transgenic tobacco cell culture (TBY2) aiming to be a sustainable “bio-factory” of isoprene for applicative purposes