Cloning And Function Analysis Of CbSAMS Gene From Chorispora Bungeana

Chorispora bungeana was an ideal material to investigate plant low temperature adaptation mechanism. Our previous comparative proteomic investigation showed that the expression level of S-adenosylmethionine synthetase (SAMS) was changed under low temperature. Based on this, this paper conducted further study and the results were shown below.First, revealed the structural feature of CbSAMS. We cloned the full length cDNA of this gene and named it CbSAMS, which was1483bp with an ORF of1182bp encoding393amino acids protein. The molecular weight and isoelectric point of this protein was42.78KDa and5.59respectively. Phylogenetic analysis showed that CbSAMS had the highest homology with Arabidopsis MT03up to97%. Amino acid sequence analysis showed that CbSAMS included the conserved C-terminal, M-terminal and N-terminal superfamily domains which contained the Met binding motif GHPDK and ATP binding motif GAGDQG, respectively. The Nuclear Export Signal (NES) peptide located on the surface of the protein.Second, demonstrated the expression pattern and expression regulation of CbSAMS. Subcellular localization reveals that CbSAMS expressed in the entire cell, but showed a significantly higher expression in the nucleus. The CbSAMS expression pattern is then analyzed by RT-PCR and GUS staining. The result shows that CbSAMS is expressed in all the tissues, but showed a significant higher expression level in roots and flowers. We also isolated the promoter region of CbSAMS gene1919bp upstream the ATG start codon, CbSAMSp, and analyzed its cis-acting elements. It is revealed that a transcription start site located320bp upstream the ATG start codon and cis-acting elements related to light, ABA, auxin, ethylene, MeJA, low temperature and drought have been found in the CbSAMSp sequence. However, the result revealed that CbRAV1hardly regulated the expression of CbSAMS. But, Y2H results have shown that CbSAMS interacts with FRIGIDA-LIKE protein which is related to flowering time control. Furthermore, the expression level of CbSAMS is induced by low temperature, ethylene and NaCl. The cis-acting elements such as DRE/CRT and LTR might involve in the up-regulation of CbSAMS under abiotic stress.Third, identified the biological function of CbSAMS under low temperature. Polyamines were ubiquitous molecule which was useful for improving plants low temperature tolerance. As a result, the polyamines content was measured by HPLC and the content of Spd increased in root after12hours-4℃treatment. This was helpful for plants survival under low temperature environments.These results further indicated that CbSAMS played an important role in plants growth and development process as well as low temperature and salt stress response in Chorispora bungeana. It provided theoretic supports for the low temperature adaptation mechanism of plants.