Tian Ai-Guo, Zhao Jing-Yun, Zhang Jin-Song, Gai Jun-Yi, Chen Shou-Yi
Plant Biotechnology Laboratory, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, 100101, Beijing, China.
Theor Appl Genet. 2004 Mar;108(5):842-50. doi: 10.1007/s00122-003-1507-6. Epub 2003 Nov 14.
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.
从大豆表达序列标签中鉴定并表征了一个全长基因GmSAMDC1，它编码参与多胺生物合成的关键酶S-腺苷甲硫氨酸脱羧酶（SAMDC）。GmSAMDC1编码一个355个氨基酸的肽。与其他植物SAMDC相比，GmSAMDC1蛋白有几个高度保守的区域，包括一个假定的酶原切割位点和一个PEST序列。GmSAMDC1 mRNA的5'前导序列包含两个额外的开放阅读框（ORF），可能调节翻译过程。GmSAMDC1基因的基因组序列在5'前导序列中包含三个内含子，但在3'-UTR或主要酶原ORF中没有内含子。在内含子2中发现了一个简单序列重复（SSR），并利用该SSR将GmSAMDC1基因定位到连锁群D1上。通过Southern杂交和PCR分析发现，GmSAMDC1基因在大豆属和野生大豆属中的基因组结构不同。还鉴定出一个假基因GmSAMDC2。该基因没有内含子，并且失去了其两个上游开放阅读框。Northern杂交分析表明，GmSAMDC1基因的表达受盐、干旱和寒冷诱导，但不受创伤诱导；这表明该基因与多种胁迫条件下的响应有关。
