Transcriptome profiling reveals divergent response strategies in two olive cultivars with contrasting drought tolerance

Understanding the transcriptional mechanisms that distinguish drought-tolerant from drought-sensitive olive cultivars is essential for improving resilience to climate change. In this study, we compared transcriptomic profiles between two olive cultivars with markedly different drought responses: the highly sensitive "Koroneiki" and the highly tolerant "Martina". Using RNA-Seq under moderate and severe drought conditions, we identified both shared and cultivar-specific transcriptional adjustments to water deficit. "Koroneiki" displayed an early and broad upregulation of genes involved in cell wall biosynthesis, secondary metabolism, and antioxidant pathways, but failed to sustain efficient hormonal regulation or timely activation of the MAP kinase signaling cascade. In contrast, "Martina" adopted an anticipatory and energy-conserving strategy, characterized by early downregulation of primary metabolism, enhanced ABA-mediated gene expression, and activation of dormancy-related pathways. Notably, key signaling nodes, such as MAP kinases, WRKY transcription factors, and ABA-GA crosstalk elements, exhibited divergent expression patterns between the two cultivars, suggesting differential engagement of regulatory networks. These findings reveal distinct transcriptomic strategies underlying drought adaptation in olive and identify "Martina" as a promising genotype for breeding programs aimed at enhancing climate resilience. The results provide molecular markers and regulatory targets for improving drought tolerance in perennial crops.