PubMed · 2026-02-19
Scientists discovered how a plant defense hormone called salicylic acid triggers the production of red pigments (anthocyanins) in apple fruit, mapping a three-protein chain that acts like a molecular switch. They also found that a second hormone, strigolactone, can dial this process back by breaking up the protein team.
A three-protein module (NPR7 → TGA6 → MYB1) forms the core salicylic acid signaling chain that directly switches on anthocyanin-making genes in apple.
When salicylic acid is absent, an enzyme called RHA2a tags the NPR7 protein for destruction via ubiquitination, effectively shutting the pathway off until defense signals return.
The strigolactone pathway antagonizes anthocyanin production by physically dismantling the NPR7-TGA6 and NPR7-MYB1 protein complexes through the repressor protein SMXL8.
