Integrative physiological and transcriptomic insights into the low-phosphorus stress response of Pinus yunnanensis var. pygmaea.

Phosphorus is an essential macronutrient regulating plant growth and development, yet the adaptive mechanisms to phosphorus deficiency in conifers remain poorly understood. In this study, we investigated the physiological and transcriptomic responses of Pinus yunnanensis var. pygmaea under prolonged low-phosphorus stress and compared its performance with Pinus massoniana and Pinus elliottii. Physiological analyses revealed that P. pygmaea is more sensitive to phosphorus deficiency, exhibiting greater metabolic impairment under stress conditions. Transcriptome profiling showed a time-dependent increase in differentially expressed genes enriched in amino acid metabolism, MAPK signaling, and flavonoid biosynthesis pathways. Weighted gene co-expression network analysis (WGCNA) identified potential regulatory interactions among phosphate-responsive genes, including SPX, ACP5, and ACP7, and transcription factors such as TALE, WRKY, and ERF, suggesting a coordinated role in maintaining ion homeostasis. These findings provide new insights into the molecular mechanisms of phosphorus stress adaptation in Pinus and offer a broader framework for understanding nutrient deficiency responses in woody plants.