Abstract. Under natural conditions, plants are exposed to a complex set of adverse environmental factors that alter their RNA expression profiles. To date, RNA-Seq studies in Quercus robur L. have typically examined responses to individual stressors, and no meta-analysis integrating multiple conditions has been performed. Therefore, the aim of our study was to conduct a meta-analysis of RNA-Seq gene expression datasets associated with drought, powdery mildew infection, and insect herbivory in order to identify differentially expressed genes (DEGs), including transcription factors (TFs). We identified four overlapping DEGs responsive to all examined stressors: histone H4, flavonol synthase, acyltransferase GLAUCE-like, and an uncharacterized gene containing a DUF1223 domain. Analysis of transcription factor profiles using the iTAK v1.6 revealed 225 TFs in total, of which 159 were associated with insect feeding, 24 with powdery mildew infection, and 42 with drought stress. Four TFs were jointly downregulated under drought and insect herbivory. Under stress caused by powdery mildew and insects, nine TFs showed altered expression, including three WRKY genes and one representative each from the AP2/ERF, NAC, MYB, and GRAS families, while the remaining two belonged to the MYB-related family. No overlap in TF expression was observed between drought stress and powdery mildew. Weighted gene co-expression network analysis (WGCNA) identified 14 modules, six of which showed the strongest association with the examined traits and were selected for hub-genes detection. In total, six hub genes were identified; three of them were automatically annotated as NAC, GDSL, and CESA3, while the remaining genes remained uncharacterized. Overall, the meta-analysis demonstrates that plant responses to diverse stressors are mediated by both stress-specific and shared molecular mechanisms. Co-expression modules and transcription factors play a central role in these responses, enabling the identification of promising candidate genes for future functional studies and breeding efforts English oak.

 

Key words: meta-analysis, RNA-seq, WGCNA, English oak (Quercus robur), drought, powdery mildew, insect herbivory