Comparative phenotypic, physiological, and transcriptomic responses to drought and recovery in two Fraxinus species

Area of Science:

• Plant Science
• Drought Stress Physiology
• Molecular Biology

Background:

• Two ash species, Fraxinus chiisanensis and F. rhynchophylla, exhibit differential drought tolerance due to distinct habitats.
• Understanding seedling response to drought is vital for breeding drought-resistant ash trees.

Purpose of the Study:

• Compare phenotypic, physiological, and transcriptomic responses to drought stress and rehydration in F. chiisanensis and F. rhynchophylla.
• Identify key genes and pathways involved in drought tolerance and recovery.

Main Methods:

• Time-course experiment involving drought stress and rehydration.
• Phenotypic measurements (growth, temperature).
• Physiological assessments (fluorescence response, stress indices, antioxidant enzyme activity).
• Transcriptome analysis (Gene Ontology, Kyoto Encyclopedia of Genes and Genomes pathways).

Main Results:

• F. rhynchophylla displayed more severe initial stress but faster recovery of growth, fluorescence, and antioxidant enzyme activity (SOD, CAT, APX) compared to F. chiisanensis.
• F. chiisanensis showed less initial growth retardation but incomplete recovery.
• Transcriptome analysis highlighted photosynthesis and enzyme activity as key responsive processes, with significant differentially expressed genes (DEGs) in F. rhynchophylla, mostly restored post-rehydration.

Conclusions:

• Significant species-specific differences exist in drought and recovery responses between F. chiisanensis and F. rhynchophylla.
• Identified genes and pathways (e.g., sugar metabolism, antioxidant enzymes, hormone signaling) provide targets for improving ash tree drought tolerance.
• Provides insights into ash tree physiological and genetic stress responses for future research.