Metabolomics and Biochemical Approaches Link Salicylic Acid Biosynthesis to Cyanogenesis in Peach Plants

Abstract

Despite the long-established importance of salicylic acid (SA) in plant stress responses and other biological processes, its biosynthetic pathways have not been fully characterized. The proposed synthesis of SA originates from chorismate by two distinct pathways: the isochorismate and phenylalanine (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 the two pathways. In this work, by metabolomics and biochemical approaches (including the use of [13C]-labeled compounds), we provide strong 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 phenylalanine, controlling their turnover. In peach plants MD is the intermediary molecule of the suggested new SA biosynthetic pathway and CNglcs turnover, regulating the biosynthesis of both amygdalin and SA. MD-treated peach plants displayed increased SA levels via benzoic acid (one of the SA precursors within the PAL pathway). MD also provided partial protection against Plum pox virus infection in peach seedlings. Thus, we propose a third pathway, an alternative to the PAL pathway, for SA synthesis in peach plants.

Maize phenylalanine ammonia‐lyases contribute to resistance to Sugarcane mosaic virus infection, most likely through positive regulation of salicylic acid accumulation

“…In Arabidopsis thaliana and barley ( Hordeum vulgare ), most SA biosynthesis is dependent on isochorismate synthase (ICS) activity (Hao et al ., ; Wildermuth et al ., ). In tobacco ( Nicotiana tabacum ) SA is predominantly synthesized from benzoic acid derived from the phenylpropanoid pathway (phenylalanine) (Lee et al ., ), in peach ( Prunus persica ) SA is also produced from benzoic acid derived from phenylalanine via an alternative pathway (Diaz‐Vivancos et al ., ), whilst in soybean ( Glycine max ) the isochorismate and phenylpropanoid pathways are equally important in supplying the carbon skeletons for SA biosynthesis (Shine et al ., ). The phenylpropanoid pathway is also involved in the biosynthesis of many plant defensive compounds, including flavonoids, lignin, condensed tannins, hydroxycinnamic acid, coumarins and stilbenes (An and Mou, ; Yu and Jez, ).…”

The effect of abiotic and biotic stress on the salicylic acid biosynthetic pathway from mandelonitrile in peach

“…In the micropropagated shoots, abiotic salt stress was imposed by adding 30 mM NaCl to the micropropagation media, whereas PPV-infected peach shoots (Clemente-Moreno et al , 2011) were used to assess the biotic stress conditions. Under in vitro conditions, all the assays were performed in the presence or absence of 200 μM [ 13 C]MD or [ 13 C]Phe (Campro Scientific GmbH, Germany), as described in Diaz-Vivancos et al (2017).…”

“…Under greenhouse conditions, GF305 peach seedlings grown in 2 L pots were first submitted to an artificial rest period (eight weeks) in a cold chamber to ensure uniformity and fast growth. The salt-stressed seedlings were then irrigated once a week with 34 mM NaCl in the presence or absence of 1 mM MD or Phe (Diaz-Vivancos et al 2017) for seven weeks. The PPV-infected peach seedlings (Hernández et al , 2004) were treated with 1 mM MD or Phe for six weeks and then submitted to an artificial rest period again, which was necessary to ensure the later multiplication of the virus.…”

“…In a previous work, we described a third pathway for SA biosynthesis from mandelonitrile (MD) in peach plants. In this pathway, MD acts as an intermediary molecule between cyanogenic glycoside turnover and SA biosynthesis (Diaz-Vivancos et al , 2017). The contribution of the different biosynthetic pathways to the total SA content varies depending on the plant species, the physiological and developmental stage, and the environmental conditions (Catinot et al , 2008; Chen et al , 2009; Dempsey et al , 2011; Ogawa et al , 2006).…”

“…For example, although it is generally accepted that the contribution of the phenylalanine (Phe) ammonia-lyase (PAL) pathway to the total SA pool is small, this pathway gains importance during plant-pathogen interactions (Liu et al , 2015). Moreover, treatment with 1 mM MD has been found to increase SA content and provide partial protection against Plum pox virus (PPV) infection in peach plants (Diaz-Vivancos et al 2017).…”