Comparative Proteomic Analyses Provide New Insights into Low Phosphorus Stress Responses in Maize Leaves

Phosphorus deficiency limits plant growth and development. To better understand the mechanisms behind how maize responds to phosphate stress, we compared the proteome analysis results of two groups of maize leaves that were treated separately with 1,000 mu M (control, +P) and 5 mu M of KH2PO4 (intervention group, -P) for 25 days. In total, 1,342 protein spots were detected on 2-DE maps and 15.43% had changed (P < 0.05; >= 1.5-fold) significantly in quantity between the +P and -P groups. These proteins are involved in several major metabolic pathways, including photosynthesis, carbohydrate metabolism, energy metabolism, secondary metabolism, signal transduction, protein synthesis, cell rescue and cell defense and virulence. The results showed that the reduction in photosynthesis under low phosphorus treatment was due to the down-regulation of the proteins involved in CO2 enrichment, the Calvin cycle and the electron transport system. Electron transport and photosynthesis restrictions resulted in a large accumulation of peroxides. Maize has developed many different reactive oxygen species (ROS) scavenging mechanisms to cope with low phosphorus stress, including up-regulating its antioxidant content and antioxidase activity. After being subjected to phosphorus stress over a long period, maize may increase its internal phosphorus utilization efficiency by altering photorespiration, starch synthesis and lipid composition. These results provide important information about how maize responds to low phosphorus stress.