Anthocyanin transcriptional profile and pigmentation pattern in the purple tomato fruit in response to light

Anthocyanins are specialized plant metabolites with significant dietary value due to their antioxidant and anti-inflammatory properties. Extensive research has indicated that dietary intake of these phenolic compounds contributes to preventing various chronic diseases. Consequently, incorporating anthocyanin-rich foods into one's diet, particularly from natural sources, is highly beneficial. The tomato (Solanum lycopersicum) is the most consumed vegetable worldwide, making it an excellent candidate for anthocyanin-enrichment strategies. The activation of anthocyanin biosynthesis is light-dependent in tomato, but this mechanism has not been entirely characterized. In this study, a purple tomato line in the cv. Micro-Tom (MT-Aft/atv/hp2) was utilized to investigate cyanic fruits developed under varying light conditions. This genotype is derived from natural genetic variation and exhibits anthocyanin accumulation starting early in fruit development. Transcriptional analyses of the fruit peel (exocarp or epicarp) and flesh (mesocarp) revealed that the bHLH transcription factor SlAN1 (Solyc09g065100) is the limiting factor for anthocyanin accumulation in both tissues. In this genotype, the absence of anthocyanin accumulation in the flesh results from the sun-blocking effect of the cyanic epicarp on the mesocarp, preventing light from penetrating deeper into the fruit during its development. This research enhances our comprehension of the genetic and environmental regulation of anthocyanin accumulation in fruit tissues, offering valuable insights for plant breeding and human nutrition. Gene expression analysis of tomato tissues (epicarp and mesocarp) developed under dark conditions followed by light exposition to evaluate the regulatory mechanism of anthocyanin accumulation in the tissues.