The Signaling And Molecular Mechanism Of Maize Drought Resistance Mediated By Extracellular ATP

The ATP molecules is a traditional energy currency of living organisms, in recent years , it is discovered that the ATP molecules also take part in the regulation of plant growth and biological response to abiotic stresses. In this study, physiology, molecular biology, pharmacology and experimental means are used to determine the exogenous ATP concentration gradient that can improve drought resistance of maize crop, clarify the network relationship between ATP signals and H₂O₂, NO, and the effect from extracellular ATP concentration to Aquaporin ZmPIP2;1, ZmPIP2;5 and its gene expression, systematically reveals extracellular ATP-mediated signaling molecules mechanism to plants' drought resistance .In this paper, different concentration of exogenous ATP(0,50,100,500,1000μM) and ATP scavengers are used on the drought resistance of maize including measure drought physiology data,Aquaporin and its gene expression change; different time gradient (0,1,2,4,8,12,24 h) of 200μM exogenous ATP are used on the effect of drought resistance in maize;five processing (ATP, ATP + DPI, ATP + DPI + HB, ATP + DPI + SNP, ATP + HB) are designed to the study of measuring drought physiology data,Aquaporin and its gene expression change to discuss extracellular ATP take part in the plant signal transduction。The main results are as follows:1. When exogenous ATP concentration is between 100 500μM, the activity of SOD, CAT,and APX are significantly increased,the content of O₂^-·, H₂O₂, soluble protein , GSH, Vc and free proline are increased, MDA content is decreased, water Mechanical conductance is increased, too. It has the opposite results when ATP scavenger are used. The result tell us that extracellular ATP as a signal molecule to enhance the drought resistance of maize.2. When HB are used, the activity of SOD, CAT, APX in the leaves of maize all decreased compared to the untreated, NO content decreased, indicating that NO is in the downstream of ATP in the signal transduction pathway .When DPI are used,the activity of SOD, CAT, APX all decreased compared to the untreated, H₂O₂content decreased, indicating that ROS is in the downstream of ATP in the signal transduction pathway .When joined SNP treatment after DPI are used, the activity of SOD, CAT, APX increased again, but H₂O₂ content didn't increase, indicating that NO is in the downstream of ROS in the signal transduction pathway. So that the extracellular ATP-mediated signaling pathway for the drought resistance is: from extracellular ATP to the reactive oxygen species and then to NO, thereby regulating the drought resistance in maize.3. Treatment of exogenous ATP, Trizol extraction of total maize root RNA, after reverse transcription quantitative PCR, the results showed that when exogenous ATP has the concentration of 500μM, aquaporin gene has the lowest expression, indicating that exogenous ATP inhibits the expression of aquaporin genes.