Genomic characterization of the S-adenosylmethionine decarboxylase genes from soybean
A full-length gene GmSAMDC1, encoding the S-adenosylmethionine decarboxylase (SAMDC), a key enzyme involved in polyamine biosynthesis, was identified from soybean expressed sequence tags and was characterized. GmSAMDC1 encoded a peptide of 355 amino acids. When compared with other plant SAMDCs, the GmSAMDC1 protein had several highly conserved regions including a putative pro-enzyme cleavage site and a PEST sequence. The 5′ leader sequence of the the GmSAMDC1 mRNA contained two additional open reading frames (ORFs), which may regulate the translational process. The genomic sequence of the GmSAMDC1 gene contained three introns in the 5′ leader sequence, but no intron in the 3′-UTR or the main pro-enzyme ORF. A simple sequence repeat (SSR) was found in intron 2, and the GmSAMDC1 gene was mapped to linkage group D1 using this SSR. The genomic organization of the GmSAMDC1 gene in the subgenus Glycine and the subgenus Soja was found to be different by Southern-blot and PCR analysis. A pseudogene, GmSAMDC2, was also identified. This gene contained no intron and lost its two uORFs. Northern-blot analysis showed that the GmSAMDC1 gene expression was induced by salt, drought and cold, but not induced by wounding; suggesting that the gene was implicated in response to multiple-stress conditions.
KeywordsPutrescine Leader Sequence Soybean Cultivar Pest Sequence SAMDC Gene
This work was supported by National Key Basic Research Special Funds, PR, China (G1998010209 and 2002CB111301).
- Chen SY, Zhu LH, Hong J (1991) Molecular biological identification of a rice salt tolerance line. Acta Bot Sin 33:569–573Google Scholar
- Evans PT, Malmberg RL (1989) Do polyamines have roles in plant development? Annu Rev Plant Physiol Plant Mol Biol 40:235–269Google Scholar
- Flores HE, Galston AW (1982) Polyamine and plant stress: activation of putrescine biosynthesis by osmotic shock. Science 217:1259–1261Google Scholar
- Franceschetti M, Hanfrey C, Scaramagli S, Torrigiani P, Bagni N, Burtin D, Michael AJ (2001) Characterization of monocot and dicot plant S-adenosyl-l-methionine decarboxylase gene families including identification in the mRNA of a highly conserved pair of upstream overlapping open reading frames. Biochem J 353:403–409CrossRefPubMedGoogle Scholar
- Li ZY, Chen SY (2000a) Differential accumulation of S-adenosylmethionine decarboxylase transcript in rice seedlings in response to salt and drought stresses. Theor Appl Genet 100:782–788Google Scholar
- Li ZY, Chen SY (2000b) Isolation and characterization of a salt and drought-inducible gene for S-adenosylmethionine decarboxylase from wheat (Triticum aestivum L.). J Plant Physiol 156:386–393Google Scholar
- Schröder G, Schröder J (1995) cDNAs for S-adenosyl-L-methionine decarboxylase from Catharanthus roseus, heterologous expression, identification of the pro-enzyme processing site, evidence for the presence of both subunits in the active enzyme, and a conserved region in the 5′ mRNA leader. Eur J Biochem 228:74-78PubMedGoogle Scholar
- Slocum RD (1991) Polyamine biosynthesis in plants. In: Slocum RD, Flores HE (eds) The biochemistry and physiology of polyamine in plants. CRC Press, Boca Raton Florida, pp 23–40Google Scholar
- Young ND, Galston AW (1983) Putrescine and acid stress: induction of arginine decarboxylase activity and putrescine accumulation by low pH. Plant Physiol 71:767–771Google Scholar
- Zhang JS, Gu J, Liu FH, Chen SY (1995) A gene encoding a truncated large subunit of Rubisco is transcribed and salt-inducible in rice. Theor Appl Genet 91:361–366Google Scholar