Physiological and molecular responses of poplar to salt stress and functional analysis of PagGRXC9 to salt tolerance.

This article focuses on the physiological and molecular mechanisms underlying salt tolerance in 84K poplar (Populus alba × Populus glandulosa) under varying NaCl concentrations. Salt stress was found to inhibit growth, photosystem activity, chlorophyll content, and carbon assimilation, while activating photoprotective mechanisms such as PGR5-dependent cyclic electron flow and antioxidant defenses including the ascorbate-glutathione (AsA-GSH) cycle. Weighted gene co-expression network analysis identified key photosynthesis-related hub genes (e.g., triose-phosphate isomerase and ferredoxin-NADP(+) reductase) that were downregulated, and antioxidant-related hub genes (e.g., glutaredoxin [GRX], glutathione peroxidase [GPX], and glutathione S-transferase [GST]) that were upregulated under salt stress. Functional validation showed that overexpression of the glutaredoxin gene PagGRXC9 enhanced salt tolerance in both yeast and 84K poplar by reducing photoinhibition and improving antioxidant capacity. These findings provide valuable genetic resources and insights for breeding salt-tolerant poplar trees.