Elucidating Drought Stress Tolerance in European Oaks Through Cross-Species Transcriptomics

Area of Science:

• Forestry and Environmental Science
• Plant Molecular Biology
• Climate Change Adaptation

Background:

• European forests face significant challenges from increasing extreme summer droughts and heatwaves due to climate change.
• These climatic shifts are projected to alter forest distribution, potentially causing substantial economic losses in forest land value.
• Understanding drought stress tolerance mechanisms is vital for the scientific and economic sustainability of forests facing future climate scenarios.

Purpose of the Study:

• To investigate the molecular patterns underlying drought stress tolerance in key European oak species.
• To identify species-specific genetic responses to drought stress.
• To uncover conserved genes and pathways involved in drought adaptation at the genus level for potential application in breeding programs.

Main Methods:

• Applied cross-species comparative transcriptomics to three major European oak species: *Quercus robur* (less tolerant), *Q. pubescens* (moderately tolerant), and *Q. ilex* (highly tolerant).
• Analyzed differentially expressed genes (DEGs) under drought stress conditions for each species.
• Conducted comparative orthologous gene family analysis to identify conserved genes across species.

Main Results:

• Identified 415 DEGs in *Q. robur*, 79 in *Q. pubescens*, and 222 in *Q. ilex*, demonstrating distinct species-specific drought stress responses.
• Characterized 517 orthologous genes potentially crucial for drought stress adaptation across the *Quercus* genus.
• Highlighted candidate genes and pathways involved in antioxidant capacity, mitochondrial respiration, water transport lignification, and suppression of senescence.

Conclusions:

• Oak species exhibit unique molecular strategies for coping with drought stress.
• A set of conserved orthologous genes plays a significant role in drought adaptation within the *Quercus* genus.
• The identified genetic knowledge provides a basis for developing climate-resilient tree breeding programs to enhance forest adaptation to climate change.