# Phytohormone-ROS Crosstalk Regulates Metal Transporter Expression in Sedum alfredii

## TL;DR

The study explores how plant hormones and reactive oxygen species interact to regulate metal transporters in a cadmium hyperaccumulating plant.

## Contribution

The study identifies hormone-specific ROS pathways as central to transporter regulation in cadmium hyperaccumulation.

## Key findings

- ABA and IAA enhance CAT activity and alleviate ROS-mediated repression of transporters.
- HMA3 and Nramp5 regulation by ABA and t-Z is H2O2-dependent.
- IAA modulates Nramp5 through a ROS-independent pathway.

## Abstract

Sedum alfredii is a cadmium (Cd) hyperaccumulator, but the regulatory mechanisms linking phytohormones and redox balance to Cd transporter expression remain unclear. In this study, we omitted external cadmium (Cd) stress to isolate and examine the interplay between phytohormone and reactive oxygen species (ROS) signaling. Exogenous treatments with abscisic acid (ABA), indole-3-acetic acid (IAA), gibberellic acid (GA3), trans-zeatin (t-Z), and H2O2 were combined with analyses of hormone levels, antioxidant enzyme activities, and transporter gene expression. Correlation and PLS-SEM analyses identified the CAT–H2O2 module as a key node: ABA and IAA enhanced CAT activity and alleviated ROS-mediated repression of transporters, while GA3 and t-Z exerted opposite effects. Functional validation using an H2O2 scavenger revealed that the regulation of HMA3 and Nramp5 by ABA and t-Z is H2O2-dependent. In contrast, IAA modulates Nramp5 through a ROS-independent pathway, while the regulatory effects of GA3 were negligible. Functional validation under Cd exposure suggests a model wherein HMA3 and Nramp5 act in a complementary manner to sequester and redistribute Cd in leaves, thereby supporting hyperaccumulation. These findings highlight hormone-specific ROS pathways as central to transporter regulation and provide mechanistic insights to improve phytoremediation efficiency.