Enhanced antioxidant activity improves deep-sowing tolerance in maize

Deep sowing has emerged as a vital agricultural strategy, particularly in arid and semi-arid regions, as it allows seeds to access water stored in deeper soil layers. This approach facilitates successful germination and establishment of crops, even in challenging environmental conditions. Previous studies have shown that the length of the maize mesocotyl is an important trait influencing deep-sowing tolerance. Several factors play a crucial role in regulating mesocotyl elongation, primarily including light, hormones, metabolites, and reactive oxygen species (ROS). Therefore, further understanding the regulatory mechanisms of mesocotyl elongation is essential for enhancing maize germination and growth under deep sowing conditions.

In this study, we identified a deep sowing-tolerant inbred line, DH65232, which showed significantly increased mesocotyl length compared to B73 under deep sowing conditions. Transcriptome analysis revealed that differentially expressed genes in the mesocotyl of the two inbred lines were mainly enriched in three pathways: hormone regulation, intermediate metabolites, and redox enzymes. Measurements of hormone content and phenotypic analysis following GA3 treatment indicated that GA3 plays a positive role in promoting mesocotyl elongation under deep-sowing stress in the inbred line DH65232. Additionally, untargeted metabolomics revealed that DH65232 exhibited a higher number of differential metabolites related to antioxidant pathway under deep-sowing stress compared to normal sowing. In deep sowing conditions, the determination of POD, CAT, SOD activities, and MDA content in the mesocotyl of B73 and DH65232 shows that DH65232 has a stronger ability to scavenge ROS.

Above all, the inbred line DH65232 exhibits a greater tolerance to deep sowing due to its stronger antioxidant activity. Our study has contributed to a deeper understanding of the complex tolerance mechanisms in maize and provided new insights for the development of new maize varieties under deep sowing conditions.