Multi-omics-based identification of purple acid phosphatases and metabolites involved in phosphorus recycling in stylo root exudates
Yuanhang Wu, Cang Zhao, Xingkun Zhao, Liyun Yang, Chun Liu, Lingyan Jiang, Guodao Liu, Pandao Liu, Lijuan Luo
Abstract
Stylo (Stylosanthes guianensis) is a tropical forage and cover crop that possesses low phosphate (Pi) tolerance traits. However, the mechanisms underlying its tolerance to low-Pi stress, particularly the role of root exudates, remain unclear. This study employed an integrated approach using physiological, biochemical, multi-omics, and gene function analyses to investigate the role of stylo root exudates in response to low-Pi stress. Widely targeted metabolomic analysis revealed that eight organic acids and one amino acid (L-cysteine) were significantly increased in the root exudates of Pi-deficient seedlings, among which tartaric acid and L-cysteine had strong abilities to dissolve insoluble-P. Furthermore, flavonoid-targeted metabolomic analysis identified 18 flavonoids that were significantly increased in root exudates under low-Pi conditions, mainly belonging to the isoflavonoid and flavanone subclasses. Additionally, transcriptomic analysis revealed that 15 genes encoding purple acid phosphatases (PAPs) had upregulated expression in roots under low-Pi conditions. Among them, SgPAP10 was characterized as a root-secreted phosphatase, and overexpression of SgPAP10 enhanced organic-P utilization by transgenic Arabidopsis. Overall, these findings provide detailed information regarding the importance of stylo root exudates in adaptation to low-Pi stress, highlighting the plant's ability to release Pi from organic-P and insoluble-P sources through root-secreted organic acids, amino acids, flavonoids, and PAPs.