The Suitable Of Mechanisms Of Different Genotype Maize(Zea Mays L.)in Phosphorus Stress

Phosphorus(P) is one of essential macronutrients for plant growth and development. However, the concentration of available inorganic phosphate(Pi) in soil is usually about1μM, which cannot present enough Pi for plant. In the main area of corn production, lack of available Pi in soil has become one of the key factors for restricting corn yield and increasing the production costs. Therefore, to exploit biological potential of crops to acquire P in soil more efficiently may be an effective strategy of using the low-phosphorus soil in agricultural production. In this study, the expression of gene and proteins in maize roots under different Pi supply level was investigated using RT-PCR, gene-chip and proteomic techniques.DSY-79and DSY-2were employed as the experimental material. The main results were summarized as follow:1. The effect of maize root morphology and physiological and biochemical characteristics under low-p stress.Under low-p stress, the different genotype maize of DSY-79and DSY-2showed substantial difference on root morphology. Because of the poor mobility of P in soil, well-developed root system is very important for plant efficient P absorption because of the limited immobility of Pi in soil. Compared to DSY-79, the average of root length, root surface area, root projected area, root volume and hair root number of DSY-2roots were all increased significantly. These changes improved the interface between the root and soil, which improved the capacity of P-acquisition of DSY-2. Acid phosphatase(APase) activity increased in different genotype under low-P stress APase, but whether under low-P or normal P condition, APase activity was significantly higher than DSY-79. The increase of APase activity accelerate the recycle of organic P in plants. Under low-P stress DSY-2root activity increased significantly to promote root absorption of P and other nutrients.2. The effect of low-P stress on gene expression in maize roots.The results of gene-chip showed that the gene numbers and up-regulated degree induced by low-P stress in DSY-2was far different from those of DSY-79. Under low-P stress the induced genes in DSY-2roots including those related to phosphorus absorption, transproted and energy metabolism, substance metabolism, cell growth and cell wall structure, transcription factor and transcriptional regulation, absorption of substance and material transport, stress response and defense, cell signaling recptors and signal transduction. The changes in expression level of these genes are of importance for enhancing P absorption capacity and improving the P use efficiency, which most likely present the major molecular mechanism for resistance to low-P stress in DSY-2.3. Confirmatory assay of low-P stress-induced genes using RT-PCRThe result of RT-PCR showed that low-P stress induced APase gene, organic acid secretion related genes, proton secretion related genes, phosphate transporters, channel protein genes, selective glycolytic pathway and secretive respiratory pathway related genes significant expression in DSY-2roots. By contrast, only a several genes, including citrate synthetase, three phosphate transporters and one channel protein gene, exhibited induced expression in DSY-79roots.4. The effect of low-P stress on proteome in maize rootsThe results of proteome showed that low-P stress had significant effects on proteome in DSY-2roots, the induced proteins included1-aminocyclopropane-1-carbox-ylate oxidase1, eukaryotic translation initiation factor5A, calmodulin, S-adenosy-1-homocysteine hydrolase, kinesin family protein, isopentenyl transferase IPT8. Under normal condition, DSY-79and DSY-2roots were significant difference, the differentially expressed proteins of DSY-2include eukaryotic translation initiation factor5A, glutathione S-transferase3, nucleoside diphosphate kinase4, peptidyl-prolyl cis-trans Isomerase, peroxiredoxin-5, GT Pase, peptide methionine sulfoxide reductase, superoxide dismutase [Cu-Zn]4A. These differentially expressed proteins may lead to the difference in root morphological development and phosphorus absorption capacity of DSY-2and DSY-79, and it also showed that the different genotype maize with different P efficiency, which led to difference characteristic of DSY-2and DSY-79.