The Histological And Cytological Studies On The Rules Of Reactive Oxygen Species And Calcium Ion During The Wheat-Stipe Rust Interaction

During the plant and pathogen interaction, the fastest and most immediate responses of plants are the Ca²⁺ increase and oxdative burst. Pathogen-induced Ca²⁺ flux and reactive oxygen species (ROS) generation play critical roles in plant defense against pathogen. some progresses have been made on the physiological function, production mechanism, chemical changes and Scavenging Systems of Ca²⁺ signal and ROS in different pathosystems.. However, little information was known about the roles of ROS generaton and Ca²⁺ flux during interaction between wheat and stripe rust. In this study, Wheat (Triticum aestivum L.) cultivar Suwon11 and stripe rust (Puccinia striifromis f. sp. tritici) strains CYR23 and CYR31 were used. Suwon11 displays HR upon infection with strain CYR23, but is susceptible to CYR31. Exogenous reagents of scavenger and inhibitors of ROS and chelant and blocking agent to the Ca²⁺ signal were injected into wheat leaves of incompatible interaction using exogenous injection technique. The effect on hypersensibility (HR) of host cells and development of stripe rust pathogen was analyzed to confirm the role of Ca²⁺ and ROS in the wheat defense reaction to stripe rust. In order to further elucidate the role of Ca²⁺ in the pathosystem, subcellular location of Ca²⁺ was also performed using cytochemical labeling technique in both compatible and in compatible interactions. The scavenger agents of ROS, SOD, CAT, APX and POD, inhibitors of ROS, DPI, chelant of Ca²⁺, EGTA, blocking agent of Ca²⁺, LaCl₃ were used to treated wheat leaves respectively. The levels of H2O2 generation and necrotic area of plant cell were obviously higher than that in controls after treated by SOD. The CAT and POD can reduce the percentage of ROS generation in a certain extent, while there was no significant difference of necrotic area compared with controls. The levels of H2O2 generation and necrosis area of plant cell after treated by ascorbic acid peroxidase (APX) were obviously lower or smaller than ones in controls. The percentage of NBT staining and necrotic area were both significantly lower than those in controls after treated by inhibitors DPI. The necrosis area was significantly smaller than that in control after treated by Ca²⁺ chelating agent and inhibitors. The results of subcellular location of Ca²⁺ in the compatible and incompatible interactions showed that, Ca²⁺ was mainly distributed in plasma membrane and intercellular located in both vacuole and intercellular space and which density was lower in compatible one. At 7 days, Ca²⁺ was mainly distributed around in hypha, necrotic cells and distorted plasma membrane in the incompatible interaction, while there was no much change in the compatible interaction compared with one at 5 days. The results showed that Ca²⁺ flux and ROS generation was closely related to HR and played an very important role in the interaction between wheat and stripe rust.