Genome-Wide Identification and Expression Analysis of the WRKY Gene Family in Eucalyptus grandis Under Drought Stress During Arbuscular Mycorrhizal Symbiosis.

Eucalyptus is an important timber species characterized by strong adaptability and rapid growth. However, adverse environmental conditions such as drought stress severely impact its growth and productivity. Arbuscular mycorrhizal (AM) fungi form beneficial symbiotic relationships with Eucalyptus root systems and significantly enhance plant stress tolerance. In this study, we identified 111 WRKY genes in Eucalyptus grandis and systematically characterized their physicochemical properties, phylogenetic relationships, gene structures, conserved motifs, synteny, and cis-acting elements. Notably, AM fungal symbiosis significantly enhanced the biomass, plant height, and root length of E. grandis seedlings under drought stress. Through integrated RNA-seq and qRT-PCR analyses, we identified 12 EgWRKY genes that responded to drought stress during AM fungal symbiosis, with their expression levels significantly elevated in AM-inoculated roots under drought conditions. These findings provide novel insights into the regulatory roles of EgWRKY genes in AM-mediated drought tolerance and establish a foundation for understanding the molecular mechanisms underlying WRKY-mediated stress responses in E. grandis.