Investigating the response of tomato (Solanum lycopersicum) to drought stress at the transcriptional and chromatin levels

Plants are frequently exposed to environmental conditions that adversely affect growth, development, or productivity, and the situation has aggravated due to the changes in global climate. Because of their sessile nature, plants developed various sophisticated mechanisms of gene regulation to respond, adapt, and survive under stressful situations. There is now ample evidence that epigenetic mechanisms, which are based on covalent modifications of DNA and histones that affect chromatin structure, contribute to the regulation of gene expression under stress conditions. Chromatin dynamics have been suggested to contribute also to stress memory, enabling plants to respond more efficiently to recurring stress. This thesis work investigates the drought stress response and memory in tomato (Solanum lycopersicum) by analyzing changes at both transcriptional and chromatin levels. Plants of two Solanum lycopersicum cultivars, Lucariello and M82, were grown in a greenhouse and subjected to moderate and prolonged drought stress, followed by a period of full recovery. By measuring key physiological parameters, it was possible to determine the stress and recovery status of the plants. Plant leaves were sampled at the end of the stress period and after complete recovery to analyze post-transcriptional histone modifications and transcriptome, by ChIP-seq and RNA-seq, respectively. In addition, to better understand if the drought stress-induced memory in tomato is mediated by epigenetic mechanisms, available mutant lines for important epigenetic regulators were analysed. In conclusion, by integrating the data from phenomics, transcriptomic, and chromatin analyses, a comprehensive view of the responses of Solanum lycopersicum to drought stress was obtained.