Comparative transcriptome analysis reveals variations of bioactive constituents in Lonicera japonica flowers under salt stress

Lonicera japonica flowers (LJF) is a traditional Chinese medicine packed with phenols constituents and widely used in the treatments of various diseases throughout the world. However, there is still very little known on how LJF identifies and resists salt stress. Here in, we systematically investigated the effect of salt on the phenotypic, metabolite, and transcriptomic in LJF. During long term stress (35 days), 1055 differential expression genes (DEGs) involved in the biosynthesis of secondary metabolites were screened through transcriptome analysis, among which the candidate genes and pathways involved in phenols biosynthesis were highlighted; and performed by phylogenetic tree analysis and multiple nucleotide sequence alignment. Ninety compounds were identified and their relative levels were compared between the control and stressed groups based on the LC-MS analysis, Putative biosynthesis networks of phenolic acid and flavonoid were con-structed with structural DEGs. Strikingly, the expression patterns of structural DEGs were mostly consistent with the variations of phenols under salt stress. Notably, the upregulation of UDP-glycosyl transferases under salt stress indicated post-modification of glycosyl transferases may participate in downstream flavonoids synthesis. This study reveals the relationships of the gene regulation and the phenols biosynthesis in LJF under salt stress, paving the way for the use of gene-specific expression to improve the yield of biocomponent.