Cloning and Expression Analysis of the B Subunit of V-H+-ATPase in Leaves of Halophyte Suaeda salsa Under Salt Stress Cloning,Expression and Purification of Urease B Subunit of Helicobacter pylori Identification of the Rice Vacuolar ATPase B Subunit Gene and Its Expression Pattern Analysis Under Phosphorus Deficiency Construction and Transference into Tobacco of Expression Vector of Phyto-secretion-type Cholera Toxin B Subunit Gene