Studies On Characteristics Of Energy Distribution And Comparative Proteomics Of Leaves Different Phosphorous Efficiency Maize Under Low Phosphorus Stress

In this study, we take Low-P tolerance mutant 99038-2P-319 that coming from cell engineering technology and the original line Qi-319 which is a skeleton maize inbred line as the materials. The photosynthesis related parameters and the distribution ratio of luminous energy were detected between Qi-319 and 99038-2P-319. Beside these, the proteome changes between Qi 319 and 99038-2P-319 were researched under normal and low-phosphorous environment to provide a basis for understanding the mechanism of responding to low-Pi as well as understanding speculate the reason of differences of photosynthesis between 99038-2P-319 and Qi 319.There were significant various about the content of biomass and phosphorus between the inbred line 99038-2P-319 and Qi319 under Pi starvation. Other than that, Pi starvation also decreased the content of chlorophyll as well as the ratio of Chla/ Chlb. The declined extent of 99038-2P-319 was much less compared with Qi319 about these characteristic. The results were shown that phosphorous starvation decreased net photosynthetic rate, stomatal conductance and transpiration rate, but increased intercellular CO2 concentration. The decrease of photosynthetic rate may be caused by no-stomatal lmilation. Maize inbred Ines 99038-2P-319 and Qi319 have different photosynthetic characteristics under Pi deficit. Compared to the Qi319, 99038-2P-319 could maintain the higher Pn under low-Pi condition. The efficiency of light energy convert to chemical energy(Fv/Fm) and the ETR of 99038-2P-319 were higher than Qi319. The distribution ratio of light energy that absorbed by chlorophyll was changed under low-phosphorous stress in maize. It is reported that the energy which entered into the photochemical reaction decreased significantly, however, the surplus of light-energy was much more than normal. Compared to Qi319, 99038-2P-319 may maintain more energy for photochemical reaction to keep up with the variation tendency of Pn and ETR. Phosphorous starvation induced ROS in leaves of maize and strengthened the capacity of antioxidant system to clear activated oxygen. Compared to Qi319, the content of ROS was much less in 99038-2P-319 under phosphorous starvation. The activities of SOD and APX had no significant variation between 99038-2P-319 and Qi319 under low-P stress. Under the same P level conditions, inorganic phosphate content in leaves of 99038-2P-319 was significantly higher than that of Qi319. We speculated that different inorganic phosphorus content in leaves may be the major factor for the variation of photosynthesis characteristics and the protein changes in maize inbred lines with low-P efficiency mutants.The expressions of proteins changed a lot between the leaves of 99038-2P-319 and Qi 319 under the same level Pi concentration. The method of TCA/ acetone were used to extract maize leaf proteins and obtained 126 spots that changed significantly in amount (P< 0.05;≥2 folds) by 2-DE. These proteins were identified by MALDI-TOF MS and classified according to Arabidopsis MATDB. The 126 identified proteins represented a large range of functional categories, including 8unknown proteins,19 proteins in protein fate,7 proteins in cell rescue,defense and virulence,6 proteins in secondary metabolism,24 proteins in energy,57 proteins in metabolism,5 proteins in transcription/cellular communication/signal transduction mechanism.Several related to photosynthesis such as Rubisco, ATP synthase, NADP-malic enzyme, SPP and PPDK accumulated much more in 99038-2P-319 than in Qi319. It is useful for maintaining natural Pn. Beside these results, compared with Qi319, some defensive proteins like molecular were also accumulated much more in 99038-2P-319. The other differential proteins were involved second metabolism; signal transduction. and transcriptional regulation were also altered observably. These results indicated that the low-phosphorous tolerance responses of maize were the complicated process that involved several metabolism pathways. This research results may offer the valuable information for better understanding low-Pi tolerability mechanism and receives phosphorus-efficiency breeding researches.