Transcriptional and phytohormonal responses to simulated animal grazing in Leymus chinensis.

Key message: Simulated animal feeding alters endogenous phytohormone levels and gene expression within related metabolic pathways, thereby regulating the growth, development, and defense mechanisms of Leymus chinensis. Leymus chinensis (Trin.) Tzvel. is a vital forage species in grassland animal husbandry, serving as the primary food source for grazing herbivores. Unraveling the mechanisms underlying herbage responses to grazing enhances our understanding of plant-animal interactions and their coevolution. In this study, we simulated grazing by applying animal saliva to L. chinensis post-clipping and conducted transcriptomic and phytohormonal analyses. Our findings revealed that differentially expressed genes (DEGs) responding to clipping but reverting to control levels after saliva treatment were enriched in a limited number of metabolic pathways. In contrast, DEGs specifically responsive to animal saliva were significantly enriched in numerous pathways related to plant growth, development, and defense. Quantitative real-time PCR (qRT-PCR) validated the expression patterns of representative DEGs, confirming the reliability of the transcriptome-based analyses. Five classes of DEGs were annotated in the plant hormone signal transduction pathway, including Auxin (IAA), Abscisic acid (ABA), Salicylic acid (SA), Cytokinin (CTK), and Jasmonic acid (JA). Phytohormone quantification revealed significant changes in hormone levels upon saliva treatment, peaking at 6 h post-treatment, which may account for the surge in DEGs observed at this time point. These results deepen our understanding of how animal saliva influences the growth and defense of L. chinensis and may inform more effective grassland management practices.