Differential modulation of metabolites induced by salt stress in rice plants

Abstract

Salinity is one of the abiotic stresses that most limit the growth and development of several crops, such as rice (Oryza sativa L.). According to previous studies, two rice cultivars, São Francisco (SF) and BRS Esmeralda (ES), exhibit contrasting salt stress tolerance in which the SF cultivar is more tolerant to salt stress than the ES cultivar at the pre-tillering stage. However, metabolic adjustments induced by differential tolerance remain to be explored. Hence, this study aimed to evaluate these cultivars under 80 mM NaCl assessing primary metabolism and physiological traits in the tillering stage in a not oxygenated nutrient solution. Salinity caused a significant increase of toxic ions negatively affecting plants' growth and photosynthesis parameters in both cultivars. Salinity reduced the total chlorophyll content, chlorophyll a fluorescence paraments, CO2 assimilation, stomatal conductance, and transpiration of both cultivars. On the other hand, carboxylation efficiency was increased only in SF cultivar. Overall, the physiological traits did not show differential tolerance to salinity in the tillering phase. Nevertheless, the metabolites modulation and activation of the GABA shunt in the SF leaves by salt stress were evident. Besides, 26 metabolites were differentially expressed in leaves and five in roots of the cultivars under salinity. Most of them were amino acids and key-sugars. In addition, glucopyranoside, lysine, ornithine, 2-aminoisobutyric, glutamine, arabitol, and 2-oxoglutaric acid were defined as potential biomarkers of salt stress in rice plants.