Metabolism Reorganization in Kale (<i>Brassica oleracea</i> L. var <i>acephala</i>) Populations with Divergent Glucosinolate Content under Thermal Stresses

Thermal stress causes the reduction in productivity and harvest quality. To adapt to different temperature ranges, plants activate protecting metabolic pathways. Previous studies have reported that stressful environments due to abiotic stresses have an impact on the accumulation of glucosinolates (GSLs) in Brassicaceae plants. In order to determine the role of GSLs in the plant response to thermal stress, we conducted a study comparing four populations with a high and low GSL content. The GSL levels were analysed at different temperatures [control (20), 12 and 32 °C], detecting that populations with a higher GSL content increased their resistance to the cold. In addition, populations subjected to the cold increased the content of indolic GSLs. Populations with high levels of GSLs show higher levels of glucobrassicin (GBS) and sinigrin (SIN) under cold temperatures than plants grown under control conditions. High temperatures have a lower impact on GSLs accumulation. To elucidate the induced metabolic changes due to the accumulation of GSLs under cold conditions, we performed an untargeted metabolomic analysis and identified 25 compounds differentially expressed under cold conditions in the populations with a high GSL content. Almost 50% of these compounds are classified as lipids (fatty amides, monoradylglycerols, diterpenes, glycosylglycerols, linoleic acids and derivatives). Organoheterocyclic and nitrogenous organic compounds are also over-represented. Therefore, the current results suggest that GSLs play a key role in cold tolerance. Although the associated molecular mechanisms have not been elucidated, the non-targeted metabolomics assay shows a significant change in the lipid profile, with compounds that need to be studied further.