Cimmino, luca (2026) Decoding abiotic stress resilience in Solanum: Transcriptional and epigenetic landscapes. [Tesi di dottorato]

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Abstract

Plant resilience to abiotic stress represents a critical challenge for modern agriculture, as conditions such as drought and salinity severely compromise crop productivity in an increasingly unstable climate. Potato (Solanum tuberosum L.), one of the world’s most important food crops, provides a valuable model for investigating the biological mechanisms underlying stress adaptation. Its wild relative, Solanum commersonii, however, exhibits remarkable natural tolerance and offers a valuable system for understanding the genetic and regulatory factors that sustain resilience. In plant stress responses, an important role is played both by secondary metabolites, including anthocyanins involved in cellular protection, and by epigenetic mechanisms that modulate gene expression and contribute to adaptive plasticity. Integrating these levels is therefore central to deciphering plant resilience. Following an introductory chapter, the Chapter II examines the response of cultivated potato (S. tuberosum) to drought stress through a comparison of four genotypes with differing pigmentation (two anthocyanin-rich and two non-pigmented). The plants were subjected to six days of water stress, followed by a rewatering phase on the seventh day. The results indicate that resilience is closely linked to the constitutive (preventive) accumulation of anthocyanins rather than their stress-induced synthesis. Molecular analysis reveals that a pre-existing pool of these pigments allows for a more flexible transcriptional response, mediated by the coordinated regulation of key genes such as DFR, AN1, and AN2, thereby optimizing oxidative protection. The Chapter III addresses an interspecific comparison between S. tuberosum (cv. Désirée) and the wild species S. commersonii (clone 1T) under prolonged salt stress (21 days), involving three increasing levels of salinity (0, 80, and 150 mM NaCl). The data highlight that the superior tolerance of S. commersonii appears to derive from greater regulatory plasticity sustained by targeted chromatin remodeling (gain of H3K4me3 and loss of H3K27me3) at key genes for antioxidant defense and phenylpropanoid metabolism, supported by ChIP-qPCR and complemented by qualitative locus-level ChIP-seq profiles (highest-quality replicate retained due to mapping constraints). Furthermore, the identification of the specific microRNA miRNA19 suggests a resource reallocation strategy toward defense, mediated by the repression of cell growth programs. The Chapter IV addresses heat stress and extends the investigation to heat stress memory (priming) in tomato (S. lycopersicum). The study demonstrates that priming establishes a transcriptional memory characterized by the anticipatory activation of thermotolerance-related pathways, including those mediated by heat shock proteins (HSPs) and chloroplast function. The results suggest that stress memory represents an additional layer of adaptation that can be exploited in combination with the use of wild relatives to develop potato cultivars with improved resistance to recurrent environmental stresses. Overall, this work demonstrates that enhanced stress tolerance emerges from the interplay between efficient metabolic pathways, dynamic transcriptional regulation, and advanced epigenetic control, providing new perspectives for breeding strategies aimed at improving crop resilience.

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