Understanding the molecular pathways associated with seed vigor.

Farmers and growers are constantly looking for high quality seeds able to ensure uniform field establishment and increased production. Seed priming is used to induce pre-germinative metabolism and then enhance germination efficiency and crop yields. It has been hypothesized that priming treatments might also improve stress tolerance in germinating seeds, leaving a sort of 'stress memory'. However, the molecular bases of priming still need to be clarified and the identification of molecular indicators of seed vigor is nowadays a relevant goal for the basic and applied research in seed biology. It is generally acknowledged that enhanced seed vigor and successful priming depend on DNA repair mechanisms, activated during imbibition. The complexity of the networks of DNA damage control/repair functions has been only partially elucidated in plants and the specific literature that address seeds remains scanty. The DNA repair pathways hereby described (Nucleotide and Base Excision Repair, Non-Homologous End Joining, Homologous Recombination) play specific roles, all of them being critical to ensure genome stability. This review also focuses on some novel regulatory mechanisms of DNA repair (chromatin remodeling and small RNAs) while the possible use of telomere sequences as markers of aging in seed banks is discussed. The significant contribution provided by Electron Paramagnetic Resonance in elucidating the kinetics of seed aging, in terms of free radical profiles and membrane integrity is reported.