Unlocking the Green Solution: Progesterone and Brassinosteroids Synergistically Enhance Progesterone Phytoremediation and Antioxidant Capacity of Solanum nigrum  L.

Abstract Aims: Progesterone (PROG) has been detected in various concentrations in the environment, with adverse effects on humans and wildlife. So, tactics to reduce the accumulation of this steroid in the environment must be studied. This work aimed the evaluation of the phytoremediation potential of PROG by Solanum nigrum L. plants and the understanding of how 2,4-epibrassinolide (24-EBL) would enhance this species’ remediation capacities. Methods: Three treatments were assembled: 1) control; 2) plants irrigated with 0.8 µM PROG; and 3) plants treated with 0.8 µM PROG but pre‑treated with a foliar application of 1 µM 2,4-EBL (PROG/24 EBL). PROG levels, and several antioxidant-related biochemical and molecular endpoints in roots and shoots were evaluated after 20 days of treatment. Results: No PROG was detected in the nutrient solution and plant tissues at the end of the treatment, indicating that plants were able to remove PROG from the irrigating solution. Lipid peroxidation significantly decreased in response to PROG in shoots and roots and the pretreatment with 24-EBL was even more effective in both organs. Also, a decrease in H2O2 levels was observed in both treatments in both organs. Plus, the exogenous application of both steroid hormones increased the plants’ antioxidant system both at the biochemical and gene expression levels. Conclusions: S. nigrum can swiftly phytoremediate PROG per se with no negative effects to its growth and the use of 24-EBL synergistically decreases oxidative damage by increasing the AOX system and enhances the PROG removal ability of the plants.