| Sumario: | Nitrogen(N) represents an essential macronutrient that fundamentally governs plant growth and development, while nitrogen use efficiency (NUE) optimization has emerged as a crucial strategy for sustainable intensification of agricultural production systems. Enhancing NUE in oat cultivars remains a significant challenge with limited mechanistic understanding. To unravel the regulatory networks involved in N stress adaptation, we conducted RNA sequencing on oat seedlings subjected to graded N treatments. We generated 54 RNA-seq libraries across three nitrogen regimes (HN, LN, DN) and three sampling timepoints (8 h, 4 d, 10 d), obtaining 737.53 Gb of high-quality sequencing data. Through a weighted correlation network analysis, we found that the transcription factor AsLBD38 is significantly downregulated under low nitrogen (LN) and nitrogen deficient (DN) stress. Functional characterization using nanoparticle-mediated siRNA silencing demonstrated that AsLBD38 suppression enhances N metabolism and photosynthetic efficiency under DN stress. Electrophoretic mobility shift assays (EMSA) confirmed direct binding of AsLBD38 to the CGGC cis-element within the AsNRT2.4 promoter region, while dual-luciferase reporter assays demonstrated that this interaction mediates transcriptional repression of AsNRT2.4. Additionally, AsLBD38 silencing improved the nitrogen balance index (NBI) and reduced flavonoid accumulation, indicating enhanced N utilization and reduced oxidative stress. The study reveals AsLBD38 as a pivotal role in N metabolism, offering new opportunities for breeding programs aimed at increasing crop performance under low nitrogen conditions while optimizing fertilizer utilization efficiency.
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