Divergent Regulatory Effects of Jasmonic Acid on Tomato Lycopene Biosynthesis Under Light and Dark Conditions

Jasmonates influence carotenoids biosynthesis, the pigments responsible for tomato fruit coloration, but their effect on carotenoids synthesis remains controversial. Lycopene is the predominant carotenoid in ripe tomato fruits, accounting for more than 90% of the total carotenoid content in the fruit. Our study clarified this paradox by demonstrating that methyl jasmonate (MeJA) affects post-harvest tomato lycopene accumulation differently depending on light conditions and we identified SlPIF1a as the central regulatory factor mediating this light-JA crosstalk. In light, MeJA enhances lycopene synthesis by directly activating the expression of the SlPSY1 gene through the SlMYC2 transcription factor. SlMYC2 also inhibits the expression of SlPIF1a, encoding a negative regulator of light signal that degrades in light and accumulates in darkness. In dark conditions, the accumulated SlPIF1a interacts with SlMYC2 inhibiting its activation on SlPSY1 expression. Additionally, the MeJA-induced acetyltransferase SlNATA1 interacts with and acetylates SlPIF1a, enhancing its repression on SlPSY1. Our research uncovers a new mechanism for the dual regulation of lycopene synthesis by jasmonic acid under different light conditions.