PagGRXC9 enhances the salt tolerance of 84 K poplar by interacting with the key SA signaling transcription factor PagTGA7b

Soil salinization is a major abiotic stress that severely limits plant growth and agricultural productivity. Glutaredoxins (GRXs), as thiol-based oxidoreductases, are well known for maintaining redox homeostasis under stress, yet their broader functional mechanisms in plants remain largely unexplored. In this study, we comprehensively investigated the role and molecular mechanisms of the CC-type glutaredoxin gene PagGRXC9 in response to salt stress in 84 K poplar ( Populus alba × P. glandulosa ). Our results show that PagGRXC9 is localized in both the nucleus and cytoplasm, and its expression is significantly induced by salt stress. Overexpression of PagGRXC9 markedly enhances salt tolerance in transgenic 84 K poplar. This improvement is attributable not only to its role in mitigating salt-induced oxidative damage, through coordination with the AsA-GSH cycle and other antioxidant enzyme systems, but also to PagGRXC9 ’s involvement in regulating the biosynthesis and signaling pathways of stress-related hormones (ABA, SA, JA). Notably, we identified a direct interaction between PagGRXC9 and PagTGA7b, which activates the SA signaling pathway to improve salt stress adaptation. Furthermore, we validated that overexpression of PagTGA7b also positively regulates salt tolerance in 84 K poplar, confirming that the SA signaling pathway may play a critical role in salt stress response. Overall, this study reveals that PagGRXC9 enhances salt tolerance in 84 K poplar by modulating both the antioxidant system and hormone signaling pathways, particularly through activation of SA signaling via interaction with PagTGA7b. These findings provide new insights into the function of GRXs in salt stress regulation and offer valuable genetic resources for breeding salt-tolerant tree species. • PagGRXC9 significantly enhances salt tolerance in 84 K poplar under salt stress. • PagGRXC9 coordinates antioxidant systems and hormone signaling under salt stress. • PagGRXC9 directly interacts with PagTGA7b to improve salt adaptation. • Overexpression of PagTGA7b can improve salt tolerance in 84 K poplar.