Integrating metabolome and transcriptome reveal flavonoids, abscisic acid and nitric oxide co-modulating freezing tolerance in Liriope spicata

Liriope spicata is an evergreen perennial ornamental groundcover with strong freezing tolerance. The leaf samples from -15oC freezing stress (with cold-acclimation) for five duration time treatments and 25oC cultured plants were collected and analyzed by metabolic and transcriptomic assays. A total of 581 differently expression metabolites, 4620 upregulation and 5824 downregulation differently expression genes, including 830 transcription factors, were identified in leaves when suffering freezing stress. Integrating metabolome and transcriptome suggested that flavonoids biosynthesis, carbohydrate metabolism, amino acid metabolism, lipids metabolism and signal transduction pathway were prominently enriched in response to freezing stress in L. spicata. Here, we identified genes and metabolites involved in flavonoids pathway, as well as abscisic acid (ABA) biosynthesis and the oxidative synthesis pathway of nitric oxide (NO), which may form a regulatory network and play a synergistic effect in osmotic adjustment, reactive oxygen species (ROS) homeostasis and stomatal closure under freezing stress. Taken together, we provided a network of flavonoids, ABA and NO co-modulation freezing tolerance in Liriope spicata.