The Arabidopsis Atplc5 In Plants The Pathogen Stress Response,

Phosphatidylinositol-specific phospholipase C (PI-PLC) known as a critical enzyme plays an important role in various signal-transduction pathways in eukaryotic cells. PI-PLC can hydrolyze phosphatidyl-inositol 4,5-biophosphate (PIP2) into two second messengers, inositol 1,4,5-trisphosphate (IP3) and 1,2-diacyl-glycerol (DAG). The IP3 mobilizes Ca²⁺ from intracellular organelles, thereby regulating Ca²⁺ and Ca²⁺/calmodulin-dependent enzymes and channels, while the DAG activates protein kinase C (PKC) which regulates the activation of many proteins through phosphorylation, including enzymes, receptors, and cytoskeletal components.The studies on PLC in animals started in 1950s. Researchers have achieved some findings on the components, regulations and functions of the PI system in animal cells. In 1980s the study on plant PLC is commenced, the first PLC gene AtPLCIS in Arabidopsis thalinana is found in 1995. PI-PLC in plants has been shown to be a wild-existed enzyme, although after a short research time.PI-PLC-mediated phosphoinositide signaling pathway performs important roles in the responses of plant cells to extra-cellular stimuli, such as osmotic stress, ABA, light, gravitational force changes, pathogen attack and prolongation of pollen tubes in pollination. It can transfer various signals from extra cells, and finally regulates the activation of the proteins including the related enzymes, receptors and so on, through a series of signaling pathways to participate in the physiological processes such as the cell growth, reproduction and all kinds of metabolism. Nowadays, most of the studies on PLC system focus on the stress-signaling transduction, few on the plant development process.Pathogen invading is one of the threatening factors during the plant development process. A lot of researches have been carried on the signaling transduction between the plants and pathogens, the molecular mechanism of the resistance and so on. Now two resistant mechanisms are discovered: hypersensitive response (HR) and systemic acquired resistance (SAR).When HR happens, symptoms of the plant resistant responses emerge, such as the forming of drying spots due to the rapid death of local plant cells round the site of pathogen invading. The ability of resistance on the other kinds of pathogen is inspired at the whole plant level. SAR is an active resistant mechanism after HR, which has two pathways: ROI-SA and ET-JA pathway. A series of signaling transduction happens from HR to SAR.Wild type Arabidopsis thalinana and two AtPLC5 antisense transgenic lines 5-10 and 5-24 are all injected through pressure infiltration by Pseudomonas Syringae DC3000 (Rpt2⁺) and 10mmol/L MgCl₂ as controls. The symptoms in the HR change greater in AtPLC5 antisense transgenic lines than those in the WT; the...