Transcriptomic landscape of tomato traditional long shelf-life landraces under low water regimes

‘Corbarino’ (COR) and ‘Lucariello’ (LUC) belong to the family of Mediterranean long shelf-life tomato landraces, producing high quality fruits under low water input cultivation regime in their traditional cultivation area. Understanding the morpho-physiological and molecular details of the peculiar drought stress tolerance of these two genotypes may be key to their valorization as breeding material. RNA sequencing of leaf samples of COR and LUC subjected to drought stress by water withholding in a semi-controlled greenhouse identified 3089 and 2135 differentially expressed genes respectively. These included COR- and LUC-specific annotated genes, as well as genes containing single nucleotide polymorphisms as compared to reference genome. Enriched Gene Ontology categories showed that categories such as response to water, oxidoreductase activity, nucleotide salvation and lipid biosynthesis-related processes were enriched among up-regulated DEGs. By contrast, growth and photosynthesis related genes were down-regulated after drought stress, consistent with leaf gas exchange and biomass accumulation measurements. Genes encoding cell wall degrading enzymes of the pectinase family were also down-regulated in drought stress conditions and upregulated in rewatering, indicating that cell wall composition/hardness is important for drought stress responses. Globally our results contribute to understanding the transcriptomic and physiological responses of representative tomato genotypes from Southern Italy, highlighting a promising set of genes to be investigated to improve tomato tolerance to drought.