AspAT orchestrates metabolic and transcriptional networks for drought adaptation in poplar.

Escalating climate-induced drought events are increasingly pushing terrestrial plants toward their physiological limits, challenging their growth and ecological acclimation. Metabolic reprogramming represents a critical adaptive strategy under water deficit, in which aspartate aminotransferase (AspAT) serves as a key node by modulating carbon-nitrogen flux, energy metabolism, and amino acid biosynthesis. Although AspAT genes have been implicated in abiotic stress responses in herbaceous species, their roles in woody plants remain poorly characterized. Here, we identified multiple drought-responsive AspAT family members in poplar and further characterized the function of AspAT10. Transgenic poplars overexpressing AspAT10 (OE) exhibited higher drought tolerance than wild-type (WT) controls, maintaining higher growth rates, greater biomass accumulation, and improved leaf water status under drought conditions. Consistent with these phenotypes, OE lines displayed elevated relative water content, photosynthetic performance, and lignin accumulation relative to WT plants. Transcriptome analysis revealed that AspAT10 overexpression was associated with the upregulation of genes involved in amino acid metabolism, as well as pathways related to cuticular wax formation. These findings suggest that AspAT10 may contribute to drought responses through coordinated regulation of metabolic and transcriptional processes, thereby supporting plant growth under drought stress.