Cloning And Expression Analysis Of S-Adenosyl-L-Methionine Synthase Gene In Musa Acuminate

Banana is a kind of typical respiration climacteric fruit, which has important theoretical and practical meanings to regulate its ripening and to study the mechanism of ripening. S-Adenosy-L-Methionine synthetase catalyzes the only known biosynthesis of SAM. In plants, SAM is a precursor in the biosynthesis of hormone ethylene .Many researches showed that ethylene played important functions to the fruits ripening. Our laboratory has already obtained the SSH fragments of SAM synthetase gene by constructing the SSH library of banana fruit and found it might be associated with fruit ripening by the result of chip analysis. On this foundation, this research carries on to its further studies, attempts to discover and to expound the SAM synthetase gene which relate to the ethylene biosynthesis.According to the known SSH fragments designed primer, a novel S-Adenosy-L-Methionine synthase gene (Mu-sams2) has been cloned from banana by RACE techniques. The Mu-sams2 clone is 1585 bp long consisting of a 1191 bp coding region encoding 396 bp amino acids. Sequence analysis in GenBank revealed that this gene shared 82% identical in the coding region at the nucleotide level, and 93% at the amino acid level with a known SAMS (Mu-sams1) gene though they have low homologous in the 5'and 3'uncoden region, Mu-sams2 shared 90%-94% identity at the amino acid level with the other plant SAM synthetase.This gene has a conserved ATP binding motif. The analysis of conserved regions of Mu-sams2 indicated that it had three very conserved SAMS regions and a littler conserved SAMS region,which was identical with the typical structures of the SAMS gene.Studies the expression of these two SAM synthetase gene by the RT-PCR method, the result demonstrated:1 These two genes expressions have the organization difference. The expression quantity of them are highest in the roots, then in the flowers to be next, the expression quantity in the fruits are also quite rich, but in the stem and leaf are the most lowly.And Mu-sams2 gene mRNA level obviously to be higher than Mu-sams1 in the banana...