Rejuvenation through Somatic Embryogenesis: Epigenetic and Telomeric Resetting in Melia volkensii

Melia volkensii is a drought-tolerant hardwood of high ecological and economic value in arid and semi-arid Africa, but conventional propagation is limited by poor seed viability and recalcitrance to regeneration. To explore molecular mechanisms of rejuvenation, we investigated telomere length and global DNA methylation in tissues derived from different propagation routes: adult micropropagation, juvenile seedlings, somatic embryogenesis, adventitious shoots, and root suckers. Telomere length, measured by Southern hybridization, varied significantly among tissue types. Adult micropropagated tissues showed the shortest telomeres (mean 5.0 kb), while juvenile seedlings (8.5 kb) and root suckers (8.9 kb) had markedly longer telomeres, suggesting a juvenile-like state. Somatic embryos (7.4 kb) and adventitious shoots (7.8 kb) exhibited intermediate lengths, indicating partial rejuvenation during regeneration. Global DNA methylation, quantified by ELISA, further distinguished somatic embryos, which showed the lowest absorbance (~ 2.0) and fold change (~ 0.88), significantly reduced compared to juvenile (~ 0.96), adventitious (~ 0.96), and adult tissues (~ 1.0). These findings demonstrate a strong link between telomere elongation, reduced 5-methylcytosine levels, and cellular rejuvenation in M. volkensii , offering valuable insights for optimizing clonal propagation and ensuring long-term genetic stability in forestry applications.