Carbon Dioxide Improves Phosphorus Nutrition by Facilitating the Remobilization of Phosphorus From the Shoot Cell Wall in Rice (Oryza sativa)

Phosphorus (P) starvation leads to increased reutilization of cell wall P in rice (Oryza sativa). Carbon dioxide (CO(2)) is involved not only in plant growth and development but also in the response to abiotic stresses. However, it remains unclear whether CO(2) affects the reutilization of cell wall P in rice when subjected to P deficiency. In the present study, elevated CO(2) (600 μl·L(−1)) significantly increased the soluble P content in shoots when compared with ambient CO(2) (400 μl·L(−1)). This positive effect was accompanied by an increase of pectin content, as well as an increase of pectin methylesterase (PME) activity, which results in P release from the shoot cell wall, making it available for plant growth. P deficiency significantly induced the expression of phosphate transporter genes (OsPT2, OsPT6, and OsPT8) and decreased the P content in the xylem sap, but elevated CO(2) had no further effect, indicating that the increased soluble P content observed in shoots under elevated CO(2) is attributable to the reutilization of shoot cell wall P. Elevated CO(2) further increased the P deficiency-induced ethylene production in the shoots, and the addition of the ethylene precursor 1-amino-cyclopropane-1-carboxylic acid (ACC) mimicked this effect, while the addition of the ethylene inhibitor aminoethoxyvinylglycine (AVG) abolished this effect. These results further support the role of ethylene in the alleviation of P deficiency under elevated CO(2). Taken together, our results indicate that the improvement of P nutrition in rice by elevated CO(2) is mediated by increasing the shoot cell wall pectin content and PME activity, possibly via the ethylene signaling pathway.