Function Analysis Of Arginase Genes(AtARGAH1, AtARGAH2) And The Response To Salt Stress And Nitrogne Sources

Arginase specific catalyzes L-arginine into L-ornithine and urea. Arginase has an important role in plant growth and development. The amino acid composition of Arabidopsis seed storage protein was analyzed, and the result showed that most nitrogen of storage protein is stored in arginine. So arginine is the main nitrogen source for seeding growth during seed germination. The expression of arginase genes were studied by in situ hybridization. It is shown that the arginase genes were expressed at the root tip during seed germination and the radicle elongation zone during the post-germination. The seeding was analyzed by Northern blot to study the relationship between arginase genes and salt stress. The result showed that arginase genes were induced in root and AtARGAHl increased more than AtARGAH2. The arginase genes were induced in leaf too, but now AtARGAH2increased more than AtARGAHl. Therefore, we speculated the expression of arginase was induced by NaC1treatment. The research between arginase genes and nitrogen utilization was studied under different nitrogen sources treatment by Northern blot. The result was that the expression of AtARGAHs were inhibited in different levels under5mM NH4Cl and10mM NH4NO3treatments in root and leaf, and the expression of AtARGAH2changed more. The expression of AtARGAHs was no significantly changes under lOmM KNO3treatment in both root and leaf. The expression of AtARGAHl was slightly inhibited in root, while the expression of AtARGAH2was induced under1mM urea treatment. And the expression of AtARGAHs was also inhibited in leaf by urea treatment, and the expression of AtARGAH2was inhibited more. Comparing the expression differences of AtARGAHs under nitrogen treatment, we can see that the inhibition of5mL NH4Cl to the expression of AtARGAHs was the most. Therefore, we speculated that it was NH4+played a main role in the inhibition of AtARGAHs expression under different nitrogen sources treatment.To know about the role of AtARGAHs in salt stress and nitrogen utilization, we analyzed the phenotypes, root length and fresh weight of mutants and overexpression lines of AtARGAHs under salt and different nitrogen sources treatments. The mutants of AtARGAHs enhanced the tolerance under100mM NaCl treatment, and overexpression lines of AtARGAH2exhibited a high sensitivity to salt stress. The seeding was severely inhibited under5mM NH4Cl treatment, and each line of Arabidopsis can not grow well. The argah2mutants were a little better than wild type and overexpression lines of AtARGAH2was inhibited significantly under NH4Cl treatment. There was no significantly different between each AtARGAHl line under NH4Cl treatment. AtARGAH1overexpression lines grown better than wild type under10mM NH4NO3and2mM urea treatments, while there was no significant in AtARGAH2lines compared to wild type.