Functional Characterization Of GS1a The Secondary Growth From Populus Simonii × P.Nigra

Glutamine synthesize(GS1a)is a key enzyme which plays an important role in nitrogen metabolism cycle.which could impact on promoting plant growth,improving nitrogen utilization and the resistance of plants.To study the effects of GS1a in secondary growth,GS1a was cloned from Populus simonii × P.Nigra and identify the function preliminary.The main contents and results are as follows:1.The cloning and bioinformatics analysis of GS1a.GSla was cloned from Populus simonii × P.nigra in length 1071 bp fragment and named PSnGS1a.Bioinformatics analysis showed:PsnGSla encoding 356 amino acids,the molecular weight was 38.99 kDa and isoelectric point PI is 5.53.The protein N terminal is ?-helix,C terminal is a ?-fold,during which the curl based.Tertiary structure of PsnGS1a is composed of two large subunits,each of the large subunit contains five small subunit.There was no transmembrane region and the signal peptide cleavage site in this protein.PsnGS1a had two domains:Gln-synt_N and Gln-synt_C.Subcellular localization prediction showed PsnGS1a belonged to cytoplasmic type.2.PsnGS1a tissue-specific expression and subcellular localizationPsnGS1a expression of the secondary growth process is significant,and has the specificity of the expression of tissue:PsnGS1a had highest expression in the roots,Secondly expression in xylem,lowest in leaves and phloem.This paper constructed pBI 121-GS1a-GFP plant expression vector and transiently expressed onion epidermal cells via gene gun,to study the subcellular localization of products expression of PsnGS1a,The results showed that there was no protein redistribution encoded by PsnGS1a which belongs to cytoplasmic,it was consistent with the results of experiment of subcellular localization prediction.3.PsnGS1a functional analysis overexpression in tobaccoOverexpression of PsnGS1a in Tobacco showed that the plant height,leaf aspect ratio,biomass and stem strength were significantly higher than the wild type;Data showed that the volume of leaf epidermis and palisade tissue has increased in Transgenic tobacco leaves through observed ultrastructural.Chlorophyll content and Photosynthetic rate were significantly higher in transgenic tobacco than that in wild type.GS activity,soluble protein and the free amino acid content which were associated with nitrogen metabolism of transgenic tobacco were increased in various degree than the wild type.The content of cellulose and hemicellulose in the stem of transgenic tobacco was significantly higher than that of the wild type,while the lignin was decreased.The genes expression of the secondary cell wall synthesis also changed in varying degrees.Secondary plant cell wall thickness was increased significantly in slices of transgenic tobacco stems by using environmental scanning electron microscope.This indicated that overexpression of PsnGS1a could promote the growth of transgenic plants,improve the biomass,photosynthetic rate and nitrogen utilization,and have some effect on plant secondary growth.