Identification and Functional Prediction of Salt/Alkali-Responsive lncRNAs during Alfalfa Germination

Abstract

Long non-coding RNAs (lncRNAs) are pivotal regulators of the abiotic stress responses in plants, yet their specific involvement in salt/alkali stress during alfalfa germination remains incompletely understood. Here, we subjected Zhongmu No.1 alfalfa (Medicago sativa L.) seeds to salt stress (20 mM NaCl and 20 mM Na2SO4 solutions) or alkali stress (5 mM NaHCO3 and 5 mM Na2CO3 solutions) treatments for 3 days, followed by total RNA extraction and RNA-seq analysis to delineate stress-responsive alfalfa lncRNAs. We identified 17,473 novel alfalfa lncRNAs, among which 101 and 123 were differentially expressed lncRNAs (DElncRNAs) under salt and alkali stress, respectively, compared to the control. Furthermore, we predicted 16 and 237 differentially expressed target genes regulated by DElncRNAs through cis/trans-regulatory mechanisms under salt or alkali stress, respectively. A functional enrichment analysis of DElncRNA target genes indicated that lncRNAs were implicated in the fatty acid metabolism pathway under salt stress, while they played a significant role in the phenylpropanoid and flavonoid biosynthesis pathway under alkali stress. Notably, lncRNAs were found to participate in the plant hormone signal transduction pathway, a common regulatory mechanism in both salt and alkali stress responses. These findings contribute to a deeper understanding of the mechanisms underlying alfalfa’s response to salt and alkali stresses.