Quantifying DNA Methylation in Response to Drought Stress in Silver Firs (Abies alba)

As future droughts are expected to increase in duration and severity due to climate change, forest managers may need to evaluate which coniferous species are the most resilient in drought events. Drought stress induces changes in physiology, including decreases in water potential, stomatal closure, pigment degradation, and leaf senescence (Jongdee et al., 2002, Munné-Bosch & Alegre, 2004, Heitholt et al., 1991). These physiological changes are associated with epigenetic regulation of gene expression in response to abiotic stressors (Alongi et al. 2025) and have been highly studied in crop plants and Arabidopsis. This project examines the photosynthetic and epigenetic response of silver fir (Abies alba) seedlings to progressive drought stress. I collected data biweekly over a six-week period on leaf photosynthetic characteristics, leaf pigment reflectance indexes, and leaf water potential. To establish genetic and epigenetic underpinnings of physiological stress responses, DNA was extracted from harvested new growth needles at mid- and end-drought timepoints. The DNA samples were analyzed through a whole-genome methylation assay to determine what percentage of the genome was methylated cytosines and to calculate the difference in percentage of overall methylation between the drought and control samples. The methylation assay revealed a significant increase in whole-genome methylation in drought-treated seedlings at the mid-drought point, indicating that epigenetic modification plays a role in drought resistance mechanisms even under mild drought stress. Observing the abiotic stress response at an epigenetic level may reveal how trees can continue to assimilate carbon efficiently and withstand abiotic stress through dynamically adjusting to drought and other changing climate conditions.