Genome-wide expression analysis of Festuca sinensis symbiotic with endophyte of reveals key candidate genes in response to nitrogen starvation.

BACKGROUND

Nitrogen is one of the essential macronutrients bulk elements affecting plant growth and yield. However, the nitrogen content in most agricultural soils today is insufficient to meet the increasing demand for crop productivity. Festuca sinensis is an important cultivated forage grass found in high-altitude regions of China. Breeding forage varieties capable of maintaining high yields under nitrogen-deficient conditions is of great significance. Despite its ecological and agricultural importance, the molecular mechanisms underlying the response of Festuca sinensis to nitrogen starvation, as well as the identification of key regulatory genes, remain largely unexplored.

RESULTS

In this study, Festuca sinensis was cultured under different nitrogen concentrations using 1/2 Hoagland nutrient solution. Significant morphological differences were observed among the treatments, and physiological experiments confirmed that Festuca sinensis experienced substantial stress under low-nitrogen conditions. Subsequently, RNA-Seq analysis was conducted with four treatment groups and two plant tissue types. We focused on the Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways enriched with Differentially Expressed Genes (DEGs) in three aspects: (1) the nitrogen starvation response of Festuca sinensis, (2) the symbiosis between Festuca sinensis and Epichloë sinensis, and (3) the response to nitrogen starvation after symbiosis. Through this analysis, we screened five key genes (FsNRT2.2, FsNRT2.4, FsC/VIF2, FsIRT1, and FsYSL15) as potentially important regulators. Additionally, protein interaction network analysis revealed several core genes that may play crucial roles in nitrogen starvation response and provide insights for breeding new Festuca sinensis germplasm with enhanced nitrogen deficiency tolerance.

CONCLUSIONS

This study is the first to screen core genes in Festuca sinensis related to its response to nitrogen starvation, its symbiosis with Epichloë sinensis, and the symbiotic response to nitrogen-deficient conditions. the key genes identified along with their enriched pathways, provide valuable insights into the molecular mechanisms underlying nitrogen starvation tolerance. These genes can be utilized to develop new Epichloë sinensis germplasm with enhanced tolerance to nitrogen deficiency and may also serve as a reference for advancing nitrogen starvation research in other plant species.