Differential expression of genes in response to salinity stress in tree tomato (Solanum betaceum)

The Andean “tree tomato” (Solanum betaceum) is an exotic fruit crop endemic to the high Andes, but principally cultivated in Colombia, Peru and Ecuador. The species displays broad agro-ecological adaptability and has proven resilient to different marginality factors, including high soil-salinity. This study presents a preliminary exploration of the genetic mechanisms underlying salinity tolerance in S. betaceum. To this end, we selected two S. betaceum genotypes contrasting in their ability to tolerate high salinity in vitro, and used differential display analysis to compare overall differences in gene expression between salinity-stressed and unstressed (control) plants in both genotypes. Overall, 171 differentially expressed transcripts (DETs) were identified; 30 of which showed homology with candidate genes associated with abiotic stress tolerance in different species. These were ascribed putative roles in stress-response, photosynthesis, cellular metabolism and cell wall metabolism. Several identified DETs (22 in total) also showed homology to proteins of unknown function. These sequences warrant further research for potentially novel abiotic stress tolerance mechanisms. Despite its inherent limitations, differential display analysis allowed us to identify and validate (via RT-qPCR) 3 salinity-stress induced DETs. Prospectively, expanding our analyses via the validation of additional DETs would likely contribute to the identification of genes which can be used as proxies for a better understanding of the regulatory, metabolic and physiological mechanisms used by S. betaceum to respond and adapt to salinity stress.