Weighted Gene Co-Expression Network Analysis Reveals Hub Genes Associated With Response to Low-Phosphorus Stress in Pueraria lobata

Phosphorus is an essential element for plant growth, and its deficiency severely limits crop productivity. To explore genetic resources for improving phosphorus use efficiency, this study investigated the differential low-phosphorus tolerance mechanisms of two kudzu (Pueraria lobata) germplasms from Australia (tolerant) and Jiangsu, China (sensitive) using hydroponics, RNA-seq, and WGCNA. The results showed that the Australian germplasm exhibited superior low-phosphorus tolerance through root morphological plasticity, which was characterized by increased root length and tip number under low phosphorus (0.05 mmol L^-1 KH₂PO₄); enhanced reactive oxygen species scavenging, with higher peroxidase and catalase activities under extremely low phosphorus (0.005 mmol L^-1 KH₂PO₄), and extensive transcriptome reprogramming, including 8896 upregulated genes in response to phosphorus deficiency. In contrast, the Jiangsu germplasm showed limited adaptive responses, with reduced root hairs and biomass under stress. WGCNA partitioned 21,734 expressed genes into 20 co-expression modules, among which the turquoise and light green modules showed significant correlations with phosphorus treatments and phenotypic traits. Genes in the turquoise module were primarily enriched in oxidative phosphorylation and phenylpropanoid biosynthesis pathways, whereas the light green module was significantly enriched in ribosome-related pathways. Five hub genes, ABCG5, TALDO, VAMP7B, EEF1AS, and RPLP0, were identified as core components of these modules. Collectively, these findings establish the Australian kudzu as a valuable germplasm resource for improving phosphorus use efficiency in crops and provide key molecular targets for precision breeding.