DNA alteration and programmed cell death during ageing of sunflower seed

Sunflower (Helianthus annuus L.) seed viability is affected by moisture content (MC) during ageing and is related to accumulation of hydrogen peroxide and changes in energy metabolism. The aim of the present work was to investigate the effect of ageing on DNA alteration events by RAPD (random amplification of polymorphic DNA) analysis and to determine whether loss of seed viability might correspond to a controlled programmed cell death (PCD). Ageing of sunflower seeds was carried out at 35 degrees C for 7 d at different MCs. The higher the MC, the lower was the seed viability. RAPD analysis showed that DNA alterations occurred during ageing especially in seeds containing a high MC. In addition, PCD, as revealed by DNA fragmentation and TUNEL (terminal deoxynucleotide transferase-mediated dUTP nick-end labelling) assay, was detected in aged seeds at MCs which resulted in similar to 50% seed viability. At the cellular level, TUNEL assay and propidium iodide staining showed that cell death concerns all the cells of the embryonic axis. The quantification of the adenylate pool highlights mitochondrial dysfunction in aged seeds containing a high MC. The involvement of oxidative burst, mitochondria dysfunction, and PCD in seed loss of viability is proposed.