# The Interplay of Light Signaling and SlAN1 Expression in Regulating Anthocyanin Accumulation in Fruit Tissues of Purple Tomatoes

## TL;DR

This study explores how light and a gene called SlAN1 control anthocyanin accumulation in purple tomatoes, focusing on how light affects fruit coloration.

## Contribution

The study reveals that the epicarp blocks light from reaching the flesh, and SlAN1 is a key regulator of light-dependent anthocyanin accumulation.

## Key findings

- Anthocyanin accumulation in the flesh is blocked by the cyanic epicarp, which prevents light penetration.
- The bHLH transcription factor SlAN1 appears to be the limiting factor for anthocyanin accumulation in both peel and flesh.
- Light-dependent regulation of anthocyanin biosynthesis is influenced by genetic and environmental factors in tomato fruits.

## Abstract

Anthocyanins are specialized plant metabolites with significant dietary value due to their anti‐inflammatory properties. Research indicates that dietary intake of these phenolic compounds contributes to preventing various chronic diseases. As the most consumed vegetable worldwide, tomato (
Solanum lycopersicum
) is an excellent candidate for anthocyanin‐enrichment strategies. In tomato, the activation of anthocyanin biosynthesis is light‐dependent, but this mechanism has yet to be entirely characterized. We investigated the role of light in anthocyanin biosynthesis in purple tomato fruits generated by combining the Anthocyanin fruit (Aft), atroviolacea (atv), and high‐pigment 2 (hp2) mutations into cv. Micro‐Tom (MT). MT‐Aft/atv/hp2 starts accumulating anthocyanins early during fruit development, but this accumulation is restricted to the peel (exocarp and epicarp). By manipulating light incidence in different fruit tissues, we determined that the absence of anthocyanin accumulation in the flesh results from the sun‐blocking effect of the cyanic epicarp on the flesh (mesocarp), thus preventing light from penetrating deeper into the fruits. Comparative transcriptional analyses of the fruit peel and flesh indicated that the bHLH transcription factor SlAN1 (Solyc09g065100) may be the limiting factor for light‐dependent anthocyanin accumulation in both tissues. This research enhances our comprehension of the genetic and environmental regulation of anthocyanin accumulation in fruit tissues, offering valuable insights into plant breeding for human nutrition.