Molecular and Physiological Mechanisms of Andira fraxinifolia under Copper and Zinc Stress
Name: LEONARDO ARENAS CAVADAS BUAIZ DE LIMA
Publication date: 19/02/2026
Examining board:
Name |
Role |
|---|---|
| DIOLINA MOURA SILVA | Presidente |
| JOSE AIRES VENTURA | Examinador Interno |
| VITOR DE LAIA NASCIMENTO | Examinador Externo |
Summary: Heavy metal contamination, particularly by copper (Cu) and zinc (Zn), has increased in coastal ecosystems associated with the Atlantic Forest, such as restinga environments, highlighting the need to identify native species capable of tolerating and mitigating such stress. In this context, this study investigated how metallothionein gene expression is associated with physiological tolerance mechanisms in Andira fraxinifolia exposed to Cu, Zn, and the combined treatment (Cu+Zn). Young plants were cultivated in a greenhouse and subjected to increasing metal concentrations using Hoagland and Arnon nutrient solution as control. The analyses included the relative expression of metallothionein genes (MT1, MT2, and MT3), metal accumulation in leaf tissues, total phenolic and flavonoid contents, antioxidant capacity, lipid peroxidation, photosynthetic pigments, and chlorophyll a fluorescence parameters. Molecular analysis revealed distinct temporal expression patterns of metallothioneins, with early induction of MT1 and MT2, suggesting an initial role in metal chelation and homeostasis, and a delayed and sustained activation of MT3, indicating its importance in maintaining detoxification during prolonged stress. These expression patterns were associated with physiological responses reflecting activation of the antioxidant system and partial maintenance of photosynthetic
efficiency. Zn exposure promoted higher oxidative stress and greater alterations in photochemical efficiency, whereas Cu more consistently stimulated the synthesis of phenolic compounds and flavonoids, enhancing antioxidant capacity. The combined metal exposure intensified metabolic responses, suggesting an integrated defense strategy. Despite exposure to metal concentrations higher than those typically found in natural environments, plants remained functionally active throughout the experimental period, with no mortality observed, demonstrating high molecular and physiological plasticity. The coordinated expression of metallothionein genes, together with enhanced antioxidant responses and relative photosynthetic stability, indicates that Andira fraxinifolia exhibits significant tolerance to heavy metals and represents a promising candidate for phytoremediation and phytostabilization strategies in contaminated coastal ecosystems.
