Comparative transcriptomic and proteomic analyses of two salt-tolerant alfalfa (Medicago sativa L.) genotypes: investigation of the mechanisms underlying tolerance to salt

Abiotic stressors such as salt stress restrict plant development and output, whichlowers agricultural profitability. In this study, alfalfa (Medicago sativa L.) varietieswith different levels of salt tolerance were examined using high-throughput RNAsequencing (RNA-Seq) and Tandem Mass Tags (TMT) technologies to study thereactions of the root systems to salt stress, from transcriptomics and proteomicsperspectives. To explore the molecular mechanisms of alfalfa under salt stressconditions, the transcriptomes and proteomics of two comparative alfalfagenotypes, Atlantic (AT) and ZhongMu-1 (ZM-1), were evaluated after 2 h and 6h of treatment with 150 mM NaCl. The results showed that under salt stress for 2h, 1810 differentially expressed genes (DEGs) and 160 differentially expressedproteins (DEPs) in AT were screened, while 9341 DEGs and 193 DEPs werescreened in ZM-1. Under salt stress for 6 h, 7536 DEGs and 118 DEPs werescreened in AT, while 11,754 DEGs and 190 DEPs were screened in ZM-1.Functional annotation and pathway enrichment analyses indicated that theDEGS and DEPs were mainly involved in the glutathione metabolism,biosynthesis of secondary metabolites, glycolysis/gluconeogenesis, carbonfixation in photosynthetic organisms, and photosynthesis pathways. A series ofgenes related to salt tolerance were also identified, including GSTL3 and GSTU3of the GST gene family, PER5 and PER10, of the PER gene family, and proteinssuch as APS and COMT, which are involved in biosynthesis of secondarymetabolites. The results of this study provide insights into salt resistancemechanisms in plants, and the related genes and metabolic pathwaysidentified may be helpful for alfalfa breeding in the future.