Significance of glutathione in the hormesis effect: a case study of the relationship between heavy metal Cd and monitoring plant Tillandsia ionantha

Abstract

With the impact of human activities on the global environment intensifies, how different organisms adapt to environmental stressors has become a critical issue, especially to the most toxic heavy metals. Hormesis effect is an effective way to adapt to the harsh environmental changes, and glutathione (GSH) has long been considered to play an important role in the generation of hormesis, but the underlying mechanisms have not been thoroughly investigated. This experiment selected heavy metal monitoring plant Tillandsia ionantha as the experimental material and subjected it to cadmium (Cd) stress with different time gradients. The activity of 5 GSH-related enzymes, the expression of 5 GSH-related functional genes, and the subcellular distribution of GSH were measured. The results showed that among all 13 biomarkers, 8 exhibited hormesis effects, accounting for 62 %, significantly higher than the frequencies of other dose-response types. With prolonged Cd treatment duration, the increase in GSH content was more pronounced in leaf mitochondria, and only mitochondrial GSH content showed a significant positive correlation with Cd content, suggesting high and stable GSH levels in mitochondria appear to be critical under environmental stress conditions. Notably, the expression of the four GSH-related functional genes peaked on the second day. Factor analysis also indicated that these genes played a positive regulatory role in hormesis, suggesting that GSH-related genes may respond more rapidly to Cd stress and play a more sensitive regulatory role in the formation of hormesis. The early activation of GSH functional genes and the optimization of GSH distribution at the subcellular level are likely the core drivers of hormesis formation, which has important implications when designing strategies aiming to promote beneficial hormesis effects in organisms.