The Research Of The Versatility Of Two Component System NtrY/NtrX

Rhizobia can symbiotically interact with legumes and fix dinitrogen molecues.It's very important for sustainable development of agriculture,forestry,animal husbandry.In nature,there are two life styles of rhizobia.In free-living conditions,rhizobia can independently use a variety of nutrients required for division.On the other hand,Rhizobium can live in host plant cells as a symbiotic status.Flavonoids,a group of aromatic compounds secreted by legumes induce Rhizobium to produce lipochitooligosaccharides(called Nod factors).Nod factors t activate multiple responses in host plant cells for preparation of rhizobial invasion.Nod factors and exopolysaccharides are required for the formation of infection threads that are thin tubes filled with rhizobia,which penetrate into root cortical tissues and deliver bacteria to nodule primordial cells.The invading rhizobia are internalized into root inner cortex cells as host-membrane-bound compartments,known as symbiosomes.The internalized rhizobia then develop into bacteroids,a differentiated form that is capable of nitrogen fixation.As we know,symbiotic nitrogen fixation between legumes and rhizobia is a process of signal transduction and exchange.Therefore,the study of both rhizobia and legumes is needed to to explore the mechanism of symbiotic nitrogen fixation.In most bacteria,two-component systems consist of key signaling network.Theresearch of rhizobial two-component systems will help us understand the molecular mechanism of symbiotic nitrogen-fixing,and it will provide a theoretical basis for Rhizobium engineering.In this paper,we use two-component system NtrY/NtrX of meliloti as research subjects,by molecular biology and genetics methods,construct a variety mutants of two-component system encoding genes ntrY and ntrX,by analyzing the different mutant phenotype such as the ability to secrete extracellular polysaccharide,movement movement,length and number of flagella and other phenoty.We analysis related gene expression using Real-time PCR.We analysis the function of two-component systems NtrY/NtrX.In my research,ntrY don't show obvious phenotype.But ntrX gene has variety of biological functions.ntrX gene can affect athletic ability,extracellular polysaccharide synthesis,flagellin.We found that ntrX regulate the expression of the encoding corresponding gene by Real-time PCR.And ntrX gene may be a new regulation system of extracellular polysaccharide synthesis.ntrX genes can also adjust the cell cycle and cell morphogenesis.Simultaneously,the mechanism needs further study.