Background: Phosphorus (P) deficiency is one of the major constraints limiting plant growth, especially in acid soils. Stylosanthes (stylo) is a pioneer tropical legume with excellent adaptability to low P stress, but its underlying mechanisms remain largely unknown. Results: In this study, the physiological, molecular and metabolic changes in stylo responding to phosphate (Pi) starvation were investigated. Under low P condition, the root growth in stylo was significantly enhanced, which was accompanied with up-regulation of expansin genes participating in cell wall loosening. Metabolic profiling analysis showed that a total of 256 metabolites with differential accumulation were identified in stylo roots responding to P deficiency, which mainly include flavonoids, sugars, nucleotides, amino acids, phenylpropanoids and phenylamides. P deficiency led to significant reduction in the accumulation of phosphorylated metabolites (e.g., P-containing sugars, nucleotides and cholines), suggesting that internal P utilization was enhanced in stylo roots. However, flavonoid metabolites, such as kaempferol, daidzein and their glycoside derivatives, were significantly increased in P-deficient stylo roots. Furthermore, the transcripts of various genes involved in flavonoids synthesis were found to be up-regulated by Pi starvation in stylo roots. In addition, the abundance of phenolic acids and phenylamides was significantly increased in stylo roots during P deficiency. The enhanced accumulation of the metabolites in stylo roots, such as flavonoids, phenolic acids and phenylamides, might facilitate P solubilization and cooperate with beneficial microorganisms in rhizosphere, and thus contributing to P acquisition and utilization in stylo. Conclusions: These results suggest that stylo plants cope with P deficiency by modulating root morphology, scavenging internal Pi from phosphorylated metabolites and enhancing accumulation of flavonoids, phenolic acids and phenylamides. This study provides valuable insights into the complex responses and adaptive mechanisms of stylo to P deficiency.

Background: Phosphorus (P) deficiency is one of the major constraints limiting plant growth, especially in acid soils. Stylosanthes (stylo) is a pioneer tropical legume with excellent adaptability to low P stress, but its underlying mechanisms remain largely unknown.Results: In this study, the physiological, molecular and metabolic changes in stylo responding to phosphate (Pi) starvation were investigated. Under low P condition, the growth of stylo root was enhanced, which was attributed to the up-regulation of expansin genes participating in root growth. Metabolic profiling analysis showed that a total of 256 metabolites with differential accumulations were identified in stylo roots response to P deficiency, which mainly included flavonoids, sugars, nucleotides, amino acids, phenylpropanoids and phenylamides. P deficiency led to significant reduction in the accumulation of phosphorylated metabolites (e.g., P-containing sugars, nucleotides and cholines), suggesting that internal P utilization was enhanced in stylo roots subjected to low P stress. However, flavonoid metabolites, such as kaempferol, daidzein and their glycoside derivatives, were increased in P-deficient stylo roots. Furthermore, the qRT-PCR analysis showed that a set of genes involved in flavonoids synthesis were found to be up-regulated by Pi starvation in stylo roots. In addition, the abundances of phenolic acids and phenylamides were significantly increased in stylo roots during P deficiency. The increased accumulation of the metabolites in stylo roots, such as flavonoids, phenolic acids and phenylamides, might facilitate P solubilization and cooperate with beneficial microorganisms in rhizosphere, and thus contributing to P acquisition and utilization in stylo.Conclusions: These results suggest that stylo plants cope with P deficiency by modulating root morphology, scavenging internal Pi from phosphorylated metabolites and increasing accumulation of flavonoids, phenolic acids and phenylamides. This study provides valuable insights into the complex responses and adaptive mechanisms of stylo roots to P deficiency.

Background: Phosphorus (P) deficiency is one of the major constraints limiting plant growth, especially in acid soils. Stylosanthes (stylo) is a pioneer tropical legume with excellent adaptability to low P stress, but its underlying mechanisms remain largely unknown. Results: In this study, the physiological, molecular and metabolic changes in stylo responding to phosphate (Pi) starvation were investigated. Under low P condition, the root growth in stylo was significantly enhanced, which was accompanied with up-regulation of expansin genes participating in cell wall loosening. Metabolic profiling analysis showed that a total of 256 metabolites with differential accumulation were identified in stylo roots responding to P deficiency, which mainly include flavonoids, sugars, nucleotides, amino acids, phenylpropanoids and phenylamides. P deficiency led to significant reduction in the accumulation of phosphorylated metabolites (e.g., P-containing sugars, nucleotides and cholines), suggesting that internal P utilization was enhanced in stylo roots. However, flavonoid metabolites, such as kaempferol, daidzein and their glycoside derivatives, were significantly increased in P-deficient stylo roots. Furthermore, the transcripts of various genes involved in flavonoids synthesis were found to be up-regulated by Pi starvation in stylo roots. In addition, the abundance of phenolic acids and phenylamides was significantly increased in stylo roots during P deficiency. The enhanced accumulation of the metabolites in stylo roots, such as flavonoids, phenolic acids and phenylamides, might facilitate P solubilization and cooperate with beneficial microorganisms in rhizosphere, and thus contributing to P acquisition and utilization in stylo. Conclusions: These results suggest that stylo plants cope with P deficiency by modulating root morphology, scavenging internal Pi from phosphorylated metabolites and enhancing accumulation of flavonoids, phenolic acids and phenylamides. This study provides valuable insights into the complex responses and adaptive mechanisms of stylo to P deficiency.

Background Low phosphorus (P) availability is a major constraint on the growth of plants, especially in acid soils. Stylosanthes (stylo) is a pioneer tropical legume with several adaptive strategies to cope with P deficiency, but its metabolic reprogramming during P limitation remain poorly understood. Results To shed light on the acclimation of stylo roots to low P stress, morphophysiological and metabolic response were investigated in this study. After 15 days of low P treatment, shoot dry weight and total P concentration were markedly hampered, whereas root growth, root APase activity, root antioxidant activity were markedly enhanced. Corresponding investigation of metabolic profiling showed that a total of 256 metabolites with differential accumulation in response to P deficiency were identified in stylo roots, mainly including sugars, organic acids, amino acids, nucleotides, phenylpropanoids and their derivatives. P deficiency leads to significant reduction in the levels of phosphorylated sugars and nucleotides, indicates that the known strategies of P scavenging from P-containing metabolites are observed. The metabolisms of organic acids and amino acids were also remodeled by P limitation, which suggests that P-deficient stylo roots redistribute their carbohydrates in responding P deprivation, by releasing organic acids into the rhizosphere to mobilize phosphate from P complexes and employing amino acids as alternative carbon resource for energy metabolism. In phenylpropanoid metabolism pathway, the increased accumulation flavonoids, as well as up-regulated expression of involved genes SgF3H, SgF3’H, SgFLS, might contribute to enhance the antioxidant activity of stylo roots, especially kaempferol, quercetin, dihydromyricetin. The enhanced accumulation isoflavonoids with differential expression of related genes (SgHID and SgUGT) supported the opinion of isoflavonoids secreted to function with rhizosphere microbes in responding to P deficiency condition, especially daidzein and rotenone. Conclusions This study provides valuable insights generated from stylo roots into the various adaptation responses to Pi-starvation, identified candidate genes and metabolites will make some contributions to detect potential target region for future developing Pi-efficiency breeding research.

Background: Phosphorus (P) deficiency is one of the major constraints limiting plant growth, especially in acid soils. Stylosanthes (stylo) is a pioneer tropical legume with excellent adaptability to low P stress, but its underlying mechanisms remain largely unknown. Results: In this study, the physiological, molecular and metabolic changes in stylo responding to phosphate (Pi) starvation were investigated. Under low P condition, the root growth in stylo was significantly enhanced, which was accompanied with up-regulation of expansin genes participating in cell wall loosening. Metabolic profiling analysis showed that a total of 256 metabolites with differential accumulation were identified in stylo roots responding to P deficiency, which mainly include flavonoids, sugars, nucleotides, amino acids, phenylpropanoids and phenylamides. P deficiency led to significant reduction in the accumulation of phosphorylated metabolites (e.g., P-containing sugars, nucleotides and cholines), suggesting that internal P utilization was enhanced in stylo roots. However, flavonoid metabolites, such as kaempferol, daidzein and their glycoside derivatives, were significantly increased in P-deficient stylo roots. Furthermore, the transcripts of various genes involved in flavonoids synthesis were found to be up-regulated by Pi starvation in stylo roots. In addition, the abundance of phenolic acids and phenylamides was significantly increased in stylo roots during P deficiency. The enhanced accumulation of the metabolites in stylo roots, such as flavonoids, phenolic acids and phenylamides, might facilitate P solubilization and cooperate with beneficial microorganisms in rhizosphere, and thus contributing to P acquisition and utilization in stylo. Conclusions: These results suggest that stylo plants cope with P deficiency by modulating root morphology, scavenging internal Pi from phosphorylated metabolites and enhancing accumulation of flavonoids, phenolic acids and phenylamides. This study provides valuable insights into the complex responses and adaptive mechanisms of stylo to P deficiency.