Exploring the molecular mechanisms of seed deterioration in the model species Medicago truncatula L. and Populus alba L.: designing anti-aging treatments to protect seeds in storage

Seed longevity is a complex trait influenced by numerous factors. It is especially significant in the context of climate change, since it is essential for advancing sustainable agriculture, germplasm conservation, and ensuring high seed quality. Seed priming is a technique employed to improve seed quality by stimulating pre-germinative metabolism, encompassing DNA damage response and antioxidant response, which facilitate superior germination performance. Despite the numerous benefits, the longevity of primed seeds is compromised. Developing optimal priming techniques that protect primed seeds against aging is an efficient strategy to expand the application of seed priming. This study examines the ability of primed Medicago truncatula seeds to withstand deterioration during storage by designing and using an experimental system to screen compounds that may protect primed seeds in storage. This research evaluated the efficacy of quercetin, rutin, and spermidine as seed priming agents to improve the response of M. truncatula seeds exposed to artificial aging. The addition of quercetin or rutin effectively mitigated the adverse effects of post-priming aging, in comparison with hydropriming, resulting in enhanced seed germination and viability. These positive effects were consistently linked to decrease in ROS levels and the concomitant enhancement in antioxidant capacity. The reported data showed that quercetin and rutin can alleviate the effects of post-priming aging by improving the seed antioxidant profile. When spermidine was applied to M. truncatula aged seeds, enhanced viability was observed. Nonetheless, improved germination percentage was associated with a higher incidence of aberrant seedlings, indicating that the protective effects of spermidine were decreased during seedling establishment. To what extent might cumulative DNA damage in seeds hinder the subsequent developmental stages? Effective DNA repair requires the inhibition of cell cycle progression, which is essential for plant development. Spermidine significantly lowered DNA damage and modified the expression of key DDR (DNA damage response) genes at different developmental stages. Results from non-targeted metabolomics highlighted that exogenous spermidine treatment triggered accumulation of endogenous polyamines, and affected antioxidants and nucleotide metabolites that could improve seed viability. These findings will improve our understanding of the deterioration mechanisms impacting the quality of primed seeds during storage and assist in the development of more mitigation techniques. Spermidine was also evaluated in a parallel study on long-term stored Populus alba clone ‘Villafranca’ seeds. Poplar seeds exhibit low viability and are categorized as intermediate seeds. Given that poplars are frequently propagated clonally, it is essential to consider the potential reduction of genetic variability within the existing germplasm. To address this issue, new populations should be developed from seeds. Soaking with solution containing spermidine significantly enhanced seed germination. Decreased ROS levels were observed in spermidine-treated seeds relative to water-soaked seeds. Increased expression of genes related to desiccation tolerance acquisition, polyamine synthesis, and antioxidant defense was observed only in dry seeds. We report the successful development of a treatment that improves the germination of long-term stored, deteriorated ‘Villafranca’ seeds, addressing current seed quality issues in poplars.Investigating the mechanisms of seed deterioration and the maintenance of seed viability improves production and storage efficiency, while also guiding suitable management and conservation techniques for seeds in long-term storage, which possess significant biological and economic value.