Metabolomics and biochemical approaches link salicylic acid biosynthesis to cyanogenesis in peach plants

Highlight Mandelonitrile, and hence cyanogenic glycosides turnover, is involved in salicylic acid (SA) biosynthesis in peach plants under control and stress conditions. A third pathway for SA synthesis in peach is proposed. Abstract Despite the long-established importance of salicylic acid (SA) in plant stress responses and other biological processes, its biosynthetic pathway has not been fully characterized. The proposed SA synthesis originates from chorismate by two distinct pathways: isochorismate and penhylalanine (Phe) ammonia-lyase (PAL) pathways. Cyanogenesis is the process related to the release of hydrogen cyanide from endogenous cyanogenic glycosides (CNglcs), and it has been linked to plant plasticity improvement. To date, however, no relationship has been suggested between both pathways. In this work, by metabolomics and biochemical approaches (including [ 13 C]-labelled compounds), we provide evidences showing that CNglcs turnover is involved, at least in part, in SA biosynthesis in peach plants under control and stress conditions. The main CNglcs in peach are prunasin and amygdalin, with mandelonitrile (MD), synthesized from Phe, controlling their turnover. In peach plants MD is at the hub of the suggested new SA biosynthetic pathway and CNglcs turnover, regulating both the amygdalin and SA biosynthesis. MD-treated peach plants displayed increased SA levels via benzoic acid (SA precursor). In addition, MD also provides partial protection against Plum pox virus infection in peach seedlings. Thus, we proposed a third pathway, alternative to the PAL pathway, for SA synthesis in peach plants.