Investigation of physiological, metabolomics analysis and HvSOS1 genes of priming with azelaic acid in barley seeds under salt stress.

Azelaic acid (AzA) is a nine-carbon dicarboxylic acid that plays a role in the systemic acquired resistance (SAR) mechanism. Upon consulting the published data on the topic, many studies were available, dedicated on the mechanism of action of azelaic acid in plants under normal conditions and biotic stress, but remarkably few on the abiotic stress. Barley seeds (Hordeum vulgare L.) from the cultivars Bülbül89 and Avcı2002 (salt tolerant and sensitive), were pre-treated with three different concentrations of azelaic acid (2, 4, 8 ppm) and later the seedlings were exposed to salt stress with 300 mM NaCl. Physiological, biochemical and molecular biological effects of AzA-treatment were examined in leaf samples. Namely, growth, relative water content (RWC), relative electrolyte leakege (REL), leaf area (LA), proline amount, lipid peroxidation product malondialdehyde (MDA), reactive oxygen species and endogenic abscisic acid (ABA) and salicylic acid (SA) levels, as well as metabolomics and SOS1 gene expression levels were determined. According to the obtained results, AzA application on seeds, reduced the oxidative damage caused by salt stress in barley plants and induced improvement in stress parameters (MDA, H2O2, O2•- content, proline and OH•- scavenging capacity). In addition, growth parameters (length and weight), chlorophyll content, RWC, LA, SA and GABA levels were suppressed, while proline, REL and metabolomics (methionine, alanine, serine, sucrose, raffinose and mannitol) increased under salt stress. Notably, after AzA application, these parameters showed significant rescue effect at a level approaching the control groups. However, AzA treatment under salt stress increased endogenous ABA levels in both cultivars, especially at higher concentrations (Bülbül89 - 4 ppm, Avcı2002 - 8 ppm). Based on these results, it was suggested that AzA can be used as an oxidative damage inhibitor or signaling molecule for increasing salt tolerance in plants. Overall, this study presents physiological, biochemical, metabolomic and gene expression data which shows that AzA protects against oxidative stress in both barley cultivars, with stronger effects in Avcı2002.