Integrating transcriptomics and metabolomics to uncover key metabolic mechanisms of mistletoe parasitism on diverse hosts

Mistletoe (Viscum coloratum (Komar.) Nakai) is a parasitic plant with medicinal and culinary uses, yet its parasitic mechanisms on host species are largely unexplored. In this study, we performed an integrated transcriptomic and metabolomic analysis of mistletoe branches and leaves parasitizing on Tilia amurensis Rupr., Ulmus pumila L., and Populus ussuriensis Kom., investigating the potential molecular and metabolic mechanisms of mistletoe influenced by these hosts. Our results revealed notable differences in the transcriptional information of mistletoe branches and leaves across various host species, which was also reflected in their metabolic profiles. At the transcriptional level, lipid metabolism, carbohydrate metabolism and amino acid metabolism were the main pathway influenced by various hosts. Flavonoids and lipids were the primary differential components in the metabolic profile of mistletoe. Combined metabolomic and transcriptomic analyses demonstrated that glycerophospholipid metabolism comprising lipids, was a vital pathway for the activities of mistletoe parasites on their hosts. In this pathway, most metabolites, such as LysoPC, and the majority of genes, such as LYPLA2 and DPP1, exhibited the highest expression levels in Tilia amurensis Rupr. Mistletoe parasitizing Tilia amurensis Rupr., whether on branches or leaves, exhibited very significant differences compared to those parasitizing Ulmus pumila L. and Populus ussuriensis Kom. The findings provide key insights into the molecular mechanisms of mistletoe’s parasitic activities and how different hosts affect its transcriptional and metabolic profiles.