Comparative Metabolome and Transcriptome Analyses Reveal Molecular Mechanisms Involved in the Responses of Two Carex rigescens Varieties to Salt Stress

Salt stress severely inhibits crop growth and production. The native turfgrass species Carex rigescens in northern China, exhibits extraordinary tolerance to multiple abiotic stresses. However, little is known about its specific metabolites and pathways under salt stress. To explore the molecular metabolic mechanisms under salt stress, we conducted metabolome analysis combined with transcriptome analysis of two varieties of Carex rigescens with differing salt tolerances: salt-sensitive Lvping NO.1 and salt-tolerant Lvping NO.2. After 5 days of salt treatment, 114 and 131 differentially abundant metabolites (DAMs) were found in Lvping NO.1 and Lvping NO.2, respectively. Among them, six amino acids involved in the amino acid biosynthesis pathway, namely, valine, phenylalanine, isoleucine, tryptophan, threonine, and serine, were accumulated after treatment. Furthermore, most DAMs related to phenylalanine biosynthesis, metabolism, and phenylpropanoid biosynthesis increased under salt stress in both varieties. The expression profiles of metabolism-associated genes were consistent with the metabolic profiles. However, genes including HCT, beta-glucosidases, and F5H, and metabolite 4-hydroxycinnamic acid, of the two varieties may account for the differences in salt tolerance. Our study provides new insights into the mechanisms underlying salt tolerance in Carex rigescens and reveals potential metabolites and genes to improve crop resilience to saline environments.