Galls and Phytochemistry: a case study of Myrtaceae superhosts with emphasis on Neomitranthes obscura

The Myrtaceae is rich in phenolics and volatile terpenoids and has many reported associations with gall inducers in Brazilian restinga. These metabolites protect plants against both biotic and abiotic stresses, but also play a crucial signaling role in plant-herbivore interactions, especially on superhosts like Neomitranthes obscura. We hypothesize that the chemical identity of the superhosts relates to their capacity to respond to diverse galling herbivores, which was assessed through a two-step bibliographic survey resulting in 52 analysed documents. The prevalent classes of chemical compounds in the superhost Myrtaceae are hydrocarbonated (SH) and oxygenated sesquiterpenes (OS), which are related to plant identity and its interactions with the galling organisms. Among the superhost Myrtaceae, Neomitranthes obscura shares sesquiterpenic and phenolic derivatives with other host plants, which makes it impossible to infer why some species are superhosts while others are not. Our results suggest that a greater diversity of terpenoids may be related to metabolic flexibility, potentially increasing the ability of hosting galling species. However, further research is needed to explore this relationship, particularly in conjunction with other key metabolite classes in Myrtaceae, such as phenolic compounds.

Keywords:
Galls; Monoterpenes; Plant-insect interactions; Sesquiterpenes; Terpenoid profile