Researchs On Molecular Cloning Of Sugarcane S-Adenosylmethionine Decarboxylase Gene And Its Genetic Transformation To Tabacco

In this study, the mORF of S-adenosylmethionine decarboxylase gene from sugarcane (Saccharum officinarum) was cloned. Sequence characteristics, biological information of coding regions and expression characteristic analysis was also conducted. It lays the foundation for the research of gene genetic transformation. The study mainly achieved the following results:(1) ScSAMDC1, ScSAMDC2 and ScSAMDC3 gene mORF from sugarcane was cloned by homologous cloning. The mORF of ScSAMDCl, whose length was 1188 bp, encoded 395 amino acid residues, and its predicted protein molecular weight was 42.78 kD. The mORF of ScSAMDC2, whose length was 1200 bp, encoded 399 amino acid residues, and its predicted protein molecular weight was 43.53kD. The mORF of ScSAMDC3, whose length was 1188 bp, encoded 395 amino acid residues, and its predicted protein molecular weight was 42.96 kD.(2) Amino acid sequence analysis indicated that, three enzymes were zymogen hydrophilic protein, and the protein structure were not stable. Moreover, the three zymogens contained two highly conserved functional domains-PEST domains and proenzyme cleavage site.(3) Phylogenetic tree analysis showed that, the amino acid sequence deduced from the ScSAMDC gene, which were more closed to gramineous plants like corn, millet, sorghum, spot spear and wheat, was in a branch of monocotyledons. However, the three SAMDC of sugarcane were not clustered into the same small branch.(4) Realtime fluorescence quantitative PCR analysis showed that, the expression of ScSAMDC2 and ScSAMDC3 were strongly induced by PEG. What's more, the effect of ScSAMDC2 was stronger than ScSAMDC3. It indicated that ScSAMDC gene may play an important role in the molecular mechanism of drought resistance in Sugarcane. Moreover, different menbers of the ScSAMDC gene familly may work differently in the regulation of polyamine.(5) The construction of plant expression vector of ScSAMDC3 gene was conducted. By using Agrobacterium tumefaciens mediated method, the ScSAMDC3 gene was transferred into tobacco. It lays the foundation for overexpression of ScSAMDC3 gene in tobacco and enhancing drought resistance of transgenic tobacco.The study further illustrated the molecular mechanism of SAMDC gene which involved in drought resistance of sugarcane, enriched the gene pool of drought resisting gene, and finally provided the candidate genes of drought resistance for other crops.