Physiological and molecular responses of poplar to drought stress and functional analysis of the key factor PagJAZ12B in JA signal transduction to drought tolerance

Identifying key genes involved in drought tolerance and clarifying their molecular mechanisms are crucial for breeding drought-tolerant poplar varieties. In this study, Populus alba × Populus glandulosa `84 K' was used as the experimental material to analyze its physiological and molecular responses to different levels of drought stress. Key drought-responsive genes were identified by weighted gene co-expression network analysis, and their functional roles were further validated. The results showed that drought significantly inhibited poplar growth, and both photosynthetic damage and oxidative damage in leaves increased with the severity of stress. RNA-seq analysis revealed that the differentially expressed genes in poplar leaves under drought stress were not only significantly enriched in photosynthesis and antioxidant-related pathways, but also enriched in plant hormone signal transduction and α-linolenic acid metabolism pathways, suggesting that jasmonic acid (JA) signaling plays a role in regulating the drought response of poplar. Based on the combined analysis of RNA-seq and weighted gene co-expression network analysis, PagJAZ12B was identified as a key gene. The overexpression lines of PagJAZ12B showed higher sensitivity to drought, as indicated by stronger inhibition of photosynthesis and more severe oxidative damage. In conclusion, the repressor gene PagJAZ12B in the JA signaling pathway negatively regulates drought tolerance in poplar, indicating that activation of the JA signaling pathway plays a positive role in the drought response of poplar. These findings provide important gene targets and a theoretical basis for improving drought tolerance in poplar through molecular breeding and for developing stress-resistant forestry varieties.