Enzymatic and nonenzymatic defenses contribute to redox homeostasis in insect-induced galls on Macairea radula (Melastomataceae)

Alterations in host cells and tissues by the galling organism involve the production of reactive oxygen species (ROS), which can promote cellular damage. However, plants possess enzymatic and nonenzymatic defense systems that scavenge ROS and prevent cellular harm. We hypothesize that gall tissues exhibit enzymatic and nonenzymatic mechanisms during their development to mitigate stress, further intensified by the entry of natural enemies. Galls on Macairea radula (Melastomataceae) induced by Palaeomystella oligophaga (Lepidoptera) were collected at different stages of development based on galling insect life stage. Mature leaves were used as comparative nongalled tissues. Fresh samples were used for enzymatic assays, whereas dried samples were used for phytochemical analysis by HPLC. The gall-inducing in larva and pupal stages did not show statistically detectable stress in galls compared with nongalled leaves, as measured by O₂ − , H₂O₂, and MDA. However, galls statistically increases the levels of phenolic compounds than nongalled organs. The activity of different enzymes during gall development converts ROS into water and oxygen, maintaining tissue homeostasis. ROS produced can also be mitigated during phenolic compound biosynthesis, providing a nonenzymatic mechanism of oxidative stress defense. Galls showed higher levels of phenolic compounds, suggesting that both enzymatic and nonenzymatic defense systems contribute to maintaining redox homeostasis in gall tissues.