Higher fruit ascorbic acid content in a tomato introgression line is associated with increased expression of genes involved in the pectin breakdown

AsA increase in tomato fruit is a desirable target and a better understanding of mechanisms involved in its synthesis and accumulation is required. Quantitative trait loci (QTLs) for AsA content in tomato fruit have been already reported using Solanum pennellii X S. lycopersicum cv. M82 introgression line (IL) population.In this study, red ripe fruit of the IL12-4 confirmed higher AsA concentration than M82 parental line over three consecutive trials. To identify differentially expressed transcripts in tomato pericarp, total RNA from the IL12-4 and the M82 was hybridized on a Combimatrix TomatArray 1.0. The comparative transcriptomic analysis identified 253 sequences as differentially transcribed. Within the differentially expressed transcripts, 61 showed up-regulation and 192 showed down-regulation. Mapping differentially expressed transcripts on metabolic networks allowed evidencing change in the expression of genes involved in the pectin breakdown process suggesting a feeding effect on the AsA pathway through D-galacturonic acid. In addition, cell wall-associated genes showed co-regulation with key genes of the ethylene biosynthesis. This finding demonstrates that transcriptomic changes occurring in the IL12-4 fruit operates through genes involved in the fruit softening and suggest that the whole process of ripening might be affected. Currently, efforts are focusing on functional characterization of candidate genes affecting expression of the fruit AsA content.