Silencing AsLBD38 enhances nitrogen metabolism by repressing AsNRT2.4 in oat (Avena sativa L.) with mesoporous silica nanoparticle delivery systems

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.