<scp>SCL15</scp> Promotes Seed Longevity Acquisition in <scp> <i>Arabidopsis thaliana</i> </scp> by Enhancing Antioxidant and Repair Mechanisms During Maturation

To ensure seed longevity and successful germination, orthodox seeds acquire protective and repair mechanisms during the late stage of seed development to counteract the detrimental effects of desiccation and subsequent rehydration, processes often associated with oxidative stress. SCARECROW-LIKE 15 (SCL15) was identified as a key regulator of seed longevity acquisition through transcriptomic profiling of maturing seeds from Arabidopsis thaliana wild type (Col-0), an SCL15 mutant, and transgenic lines overexpressing SCL15 under the seed-specific Napin promoter. SCL15 influences pathways associated with reactive oxygen species (ROS) detoxification, chlorophyll degradation, DNA and protein repair, and the accumulation of protective molecules, including late embryo abundant proteins, heat shock proteins, raffinose family oligosaccharides, and 12S globulins during seed maturation. Loss of SCL15 function impaired seed vigor and storability, accompanied by elevated ROS levels, chlorophyll retention, and reduced antioxidant capacity during seed maturation and dry storage. In contrast, SCL15 overexpression enhanced antioxidant activity, chlorophyll breakdown, and the accumulation of protective and repair factors. Together, these findings indicate that SCL15 contributes to maintaining seed viability by coordinating antioxidant defenses with protective and reparative systems during seed maturation, thereby promoting desiccation tolerance and the acquisition of longevity. In addition, the present results, together with our previous work, suggest that SCL15 may participate in integrating hormonal and circadian pathways to balance dormancy release with the acquisition of seed longevity.