Transcriptome-Wide Identification and Nitrogen-Responsive Expression Analysis of the NF-Y Transcription Factor Family in Tall Fescue

Nitrogen (N) is a critical macronutrient for plant growth, and nitrogen deficiency severely limits turfgrass and forage productivity. Nuclear Factor Y (NF-Y) is a conserved transcription factor family known to regulate plant development and stress responses. Tall fescue (Festuca arundinacea) is a perennial grass widely used as turf and forage due to its strong stress tolerance and low input requirements, making it an ideal model for studying adaptation to nitrogen limitation. However, the NF-Y family and its involvement in nitrogen responsiveness remain largely unexplored in perennial grasses. In this study, ten NF-Y genes (FaNF-Ys) were identified from the tall fescue transcriptome, including two FaNF-YA, six FaNF-YB, and two FaNF-YC members. The expansion of the FaNF-YB subfamily suggests potential functional diversification. Phylogenetic and conserved motif analyses revealed high conservation of NF-Y proteins among grasses and distinct structural characteristics among subfamilies. Expression profiling showed that most FaNF-Y genes were responsive to nitrogen availability and exhibited strong tissue specificity, with many preferentially expressed in lateral roots. Among them, FaNF-YB8 displayed a unique expression pattern, being predominantly expressed in mature leaves and showing a bidirectional response to nitrogen supply, with expression peaks at 6–12 h under low nitrogen stress and significant induction under high nitrogen conditions. This study represents the first systematic characterization of the NF-Y genes family in tall fescue and provides valuable candidate genes for understanding nitrogen adaptation and improving nitrogen use efficiency in turfgrass breeding.