DNA methylation and integrity in aged seeds and regenerated plants

Seed longevity is a complex process of key ecological and agronomic importance. DNA damage is a significant factor affecting seed ageing. Likewise, epigenetic changes can control gene expression and, therefore, seed response to ageing. The aim of the present work was to investigate the effect of ageing on nucleic acid stability and to identify reliable molecular markers that might help to monitor epigenetic changes within plant genetic resources during conservation. DNA profiles, evaluated by RAPD (random amplified polymorphic DNA), and methylation patterns, obtained by MSAP (methylation-sensitive amplification polymorphism), were compared in non-aged and aged Mentha aquatica seeds and plants produced by them. Germination decreased to 50% by storing seeds at 35 degrees C and 12% wc for 28 days. RAPD profiles were 99% similar in these aged seeds compared to non-aged seeds. However, seedlings produced from the aged seeds showed a 13% dissimilarity compared to seedlings produced from the non-aged seeds. About 8% difference in the MSAP epigenetic profile was detected in seeds after storage and 16% difference was detected in the seedlings produced from them. This indicates that stress from high temperature and humidity during storage induced changes on the methylation state of seeds, and that changes were also detectable in the regenerated plants. Our results suggest that DNA integrity was compromised in seeds during ageing, and on seedlings produced by aged seeds. Genotype screening techniques such as RAPD and MSAP have the potential as markers of nucleic acid stability during seed ageing.