Mistletoe effects on the host tree Tapirira guianensis: insights from primary and secondary metabolites

Mistletoes are parasitic plants that are capable of penetrating the living tissue of another plant’s stems and branches and extracting the necessary resources for their survival. This study aimed to compare the leaves and branches of parasitized and non-parasitized Tapirira guianensis host trees to gain insights of reciprocal effects of Phoradendron perrottetii (mistletoe) infection and profiles of primary metabolites and phenolic compounds of T. guianensis. Our hypothesis was that either the host’s chemical profile determines mistletoe infestation, or that the mistletoe infestation leads to fundamental changes in the metabolite profile of the host. Plant material was collected from T. guianensis parasitized by P. perrottetii, yielding samples from infested and non-infested host branches and their respective leaves. Infested branches were divided into two regions, the proximal region and the host-parasite interface (gall) region. Leaves and branches of non-parasitized plants were also collected. Statistical analyses revealed negative effects of the parasite on infested branches regarding most of the analyzed primary metabolites, especially soluble carbohydrates. This suggests a flow of carbohydrates towards the mistletoe, indicating a partially heterotrophic nutrition. Additionally, we observed a positive effect on the tannin contents of non-infested host branches caused by the mistletoe, which might suggest that this parasitic relationship induces a systemic response in T. guianensis. Finally, high contents of flavonoids at the gall region could indicate a mechanism of ROS quenching.