Metabolomics analysis of milk thistle lipids to identify drought-tolerant genes

Abstract

Milk thistle is an oil and medicinal crop known as an alternative oil crop with a high level of unsaturated fatty acids, which makes it a favorable edible oil for use in food production. To evaluate the importance of Milk thistle lipids in drought tolerance, an experiment was performed in field conditions under three different water deficit levels (Field capacity (FC), 70% FC and 40% FC). After harvesting seeds of the plant, their oily and methanolic extracts were isolated, and subsequently, types and amounts of lipids were measured using GC–MS. Genes and enzymes engaged in biosynthesizing of these lipids were identified and their expression in Arabidopsis was investigated under similar conditions. The results showed that content of almost all measured lipids of milk thistle decreased under severe drought stress, but genes (belonged to Arabidopsis), which were involved in their biosynthetic pathway showed different expression patterns. Genes biosynthesizing lipids, which had significant amounts were selected and their gene and metabolic network were established. Two networks were correlated, and for each pathway, their lipids and respective biosynthesizing genes were grouped together. Four up-regulated genes including PXG3, LOX2, CYP710A1, PAL and 4 down-regulated genes including FATA2, CYP86A1, LACS3, PLA2-ALPHA were selected. The expression of these eight genes in milk thistle was similar to Arabidopsis under drought stress. Thus, PXG3, PAL, LOX2 and CYP86A1 genes that increased expression were selected for protein analysis. Due to the lack of protein structure of these genes in the milk thistle, modeling homology was performed for them. The results of molecular docking showed that the four proteins CYP86A1, LOX2, PAL and PXG3 bind to ligands HEM, 11O, ACT and LIG, respectively. HEM ligand was involved in production of secondary metabolites and dehydration tolerance, and HEM binding site remained conserved in various plants. CA ligands were involved in synthesis of cuticles and waxes. Overall, this study confirmed the importance of lipids in drought stress tolerance in milk thistle.

Reconstruction and analysis of the gene regulatory network for cell wall function in <i>Arabidopsis thaliana</i> L. leaves in response to water deficit

“…Various studies have shown that plants remodel lipid composition in response to drought (Gigon et al, 2004;Liu et al, 2021). In experiments on milk thistle, it was demonstrated that under drought conditions, PLA2-ALPHA (AT2G06925), which encodes a secretory phospholipase A2 enzyme, had reduced expression (Ghanbari Moheb Seraj et al, 2022), which is also evident in our results. Secreted PLA2s are low molecular weight calcium-dependent enzymes, which specifically hydrolyze the sn-2 position of phospholipids and can do that in an organized membrane (Mariani, Fidelio, 2019).…”

Identification of responsive genes to multiple abiotic stresses in rice (Oryza sativa): a meta-analysis of transcriptomics data

“…A meta-analysis was conducted to identify genes responsible for a wide range of abiotic stresses including drought, salinity, cold and high temperatures, alkali conditions, iron, aluminum, heavy metal toxicity, and nitrogen, phosphorus, and potassium deficiency. Plants change their transcriptome profile to endure unfavorable environmental conditions in response to different stresses 42 , 43 . Despite having a specific response to each stress in plants, this study indicates that there are a vast number of genes that are similarly expressed in response to different abiotic stresses, indicating that there is a core response system to all environmental stresses in rice.…”

Identification of drought-tolerant hub genes in Iranian KC-2226 genotype of Aegilops tauschii using transcriptomic analysis

“…Biotic and abiotic stresses including drought affect the quality and yield of wheat, leading the research toward the understanding of the molecular mechanism of plant responses to stress 7 – 10 . Plants adopt different cellular responses including stomatal closure, activating transcription, changing the membrane stability, accumulating osmoprotectants and antioxidants, and scavenging reactive oxygen species (ROS) under drought stress 11 , 12 . These processes are regulated by the expression of different genes at the transcription level.…”