Determining the Link Between Genome Integrity and Seed Quality

Seed quality is of paramount importance to agriculture, food security and plant conservation programs. However, our understanding of the molecular aspects determining seed quality is far from complete, and the influence of environmental conditions during seed development and post-harvest storage are poorly characterised. There is accumulating evidence that DNA damage, response and repair mechanisms are major factors that control germination performance. Here, levels of DNA damage were analysed to determine the effects of unfavourable environments during seed development and deterioration in storage on genome integrity. In response to DNA damage, plants display a highly specific transcriptional response to double strand breaks (DSBs). This response was found to be highly sensitive to seed ageing. A slight reduction in seed vigour accompanied a reduced ability to respond effectively to DNA damage upon imbibition, indicating that an impaired DNA damage response is an early symptom of seed deterioration. Analysis identified the specific forms of DNA damage associated with seed ageing. Levels of single strand DNA breaks (SSBs) increased with loss of seed viability. Similarly DNA base damage, in the form of 8oxoG residues, increased in the dry seed following accelerated ageing. Evidence of repair of this base damage was identified within nine hours imbibition. Suboptimal temperature in the maternal environment did not significantly influence levels of these lesions, consistent with pathways mitigating DNA damage active during seed development. A requirement for antioxidant activity in genome protection was also studied using mutants with reduced levels of the antioxidant vitamin C. Understanding the molecular differences seen between high quality seeds and those that have undergone different degradation conditions provides insight into the process by which seeds lose the capacity to germination. Future analysis in different species will determine the utility of DNA damage related biomarkers for seed quality and identify potential genetic targets to improve seed performance.