Project description:Phenotypes of the tomato (Solanum lycopersicum L.) high pigment-2dg (hp-2dg) mutant are caused by a mutation in the gene encoding DEETIOLATED1, a negative regulator of light signaling. Homozygous hp-2dg plants display a plethora of distinctive developmental and metabolic phenotypes in comparison to their normal isogenic counterparts. This mutant is however best known for the increased levels of lycopene and other plastid-accumulating functional metabolites. In this study we analyzed the transcriptional alterations in mature-green, breaker and early-red fruits of hp-2dg/hp-2dg plants in relation to their normal counterparts using microarray technology. Results show that a large portion of the genes that are affected by hp-2dg mutation, display a tendency for up- rather than down-regulation. Ontology assignment of these differentially regulated transcripts, revealed a consistent upregulation of those related to chloroplast biogenesis and photosynthesis in hp-2dg mutants throughout fruit ripening. A tendency of upregulation was also observed in structural genes involved in phytonutrient biosynthesis. However, this upregulation was not as consistent, positioning plastid biogenesis as an important determinant of phytonutrient overproduction in hp-2dg mutant fruits. Microscopic observations revealed a highly significant increase in chloroplasts size and number in pericarp cells of mature-green hp-2dg/hp-2dg fruits in comparison to their normal counterparts. This increase could be observed from early stages of fruit development. Therefore, the molecular trigger that drives phytonutrient overproduction in hp-2dg mutant fruits should be initially traced at early stages of fruit development. Keywords: Comparative Transcriptional Profiling of tomato fruit pericarp tissue
