PnsSuSy2 Function Analysis Of Secondary Growth From Populus Simonii ×P.Nigra

Sucrose synthase(SuSy)is a key enzyme that regulate sucrose metabolism.Especially SuSy play an important role in secondary growth.SuSy is a key enzyme in the formation and accumulation of cellulose.Populus simonii×P.nigra may take advantage of molecular breeding to improve wood formation and cellulose content.Populus simoniixP.nigra with higher fiber length and cellulose content which is a good pulpwood.we cloned SuSy2 gene from Populus simonii ×P.nigra.The project did a preliminary study on secondary growth.Using primers based on SuSy2 gene secquences of P.trichocarpa,A 2412bp cDNA sequence was cloned by RT-PCR method.PnsSuSy2 encod a deduced amino acid sequence of 385 residues,with a molecular weight of 92.2k Da and an isoelectric point of 6.0.Analysis of amino acid sequence showed 98%homology of PnsSuSy2 from Populus trichocarpa.The enzyme is a member of GT1_Sucrose_synthase.To study the properties of the PnsSuSy2 protein,PnsSuSy2 was expressed in onion epidermal cells by gene gun method.Fluorescence was found in the cytoplasm,the cell membrane,nucleus.RT-PCR and real-time fluorescent quantitative PCR were used to investigate the PnsSuSy2 gene expression pattern in different tissues.The results showed that the highest expression of PnsSuSy2 gene occured in xylem.The expression in phloem and cambium were higher compared with mature leaf and root,while the lowest expression was found in young leaf.To determine the function of PnsSuSy2,PnsSuSy2 was expressed in N.benthamiana by the Agrobacterium mediated method.Enzyme activity,The results showed that Chlorophyll content,fructose and glucose increased significantly.Sucrose content did not change significantly.holocellulose content and fiber length increased significantly.while the lignin content did not change significantly between the transgenic and wild tobaccos.Lodg-ing resistance of transgenic tobaccos enhanced significantly.Cell walls did not change significantly by staining of transgenic tobacco stems.The biomass did not change significantly.