Cold tolerance identification of nine L. materials and expression patterns of genes related to cold tolerance in .

Members of the genus have a high ornamental value, but their cultivation area is limited by their sensitivity to cold temperatures. The aim of this study was to evaluate the cold tolerance of a range of materials, and then determine which genes were related to cold tolerance. Nine materials were subjected to a cold treatment. To identify genes related to cold tolerance, was treated at -15°C for 10 min, and leaves collected before and after this treatment were collected for RNA-Seq analyses. The transcript profiles of four DEGs (, and ) in were determined by qRT-PCR at 0 h, 1 h, 2 h, and 3 h at -15°C. Nine materials were subjected to a cold treatment, and the most cold-tolerant materials were identified as those that showed the lowest levels of electrolyte leakage and the best recovery after 30 d of growth. The most cold-tolerant materials were 'Pingyin 12', and . In total, 204 significantly differentially expressed genes (DEGs) were identified, of which 88 were significantly up-regulated and 116 were significantly down-regulated under cold conditions. Gene Ontology classification and Kyoto Encyclopedia of Genes and Genomes pathway analyses showed that the DEGs were enriched in 57 pathways, especially starch and sucrose metabolism, phenylpropane biosynthesis, MAPK signaling, fructose and mannose metabolism, and oxidative phosphorylation. By transcriptional analysis, , which was related to H ATPase activity, was continuously up-regulated, but the transcript levels of , and fluctuated during the freezing treatment. This research uncovered scarce cold-resistant materials and layed the foundation for further research on the cold tolerance mechanism of plants and the breeding of cold-tolerant varieties.