Molecular cloning of the cDNA encoding aspartate aminotransferase from bean root nodules and determination of its role in nodule nitrogen metabolism.
Molecular cloning of the cDNA encoding aspartate aminotransferase from bean root nodules and determination of its role in nodule nitrogen metabolism.
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DOI：
10.1093/jxb/erg161
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发表时间：
2003-06
影响因子：
6.9
通讯作者：
S. Silvente;A. Camas;M. Lara
中科院分区：
文献类型：
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作者：
S. Silvente;A. Camas;M. Lara
从菜豆菜豆根瘤cDNA文库中分离到一个编码天冬氨酸转肽酶（PVAAT-2） （EC 2.6.1.1）的cDNA克隆。对全长cDNA进行核苷酸序列分析，与序列数据库进行比对鉴定。大豆PvAAT-2的氨基酸序列与其他豆科植物的AAT-2亚型具有高度的相似性。PvAAT-2的氨基末端区域包含一个序列，该序列具有质体转运肽的共同特征。Southern blot分析表明，PvAAT-2克隆是由P. vulgaris基因组中的单个基因编码的。对PvAAT-2 mRNA水平的分析表明，该基因的表达在结节性增强。PvAAT-2转录物在酰胺合成增加的结节中更丰富，在尿素积累的条件下下调。当植物补充尿素或酰胺时，PvAAT-2的表达降低，而当植物补充尿素合成抑制剂别嘌呤醇时，PvAAT-2的表达不受影响。另一方面，天冬酰胺合成酶（另一种参与酰胺合成的酶）的表达不受脲类或酰胺类的影响。这些数据表明AAT-2在大豆根瘤中氮化合物合成的机制中起作用。
A cDNA clone encoding aspartate aminotransferase (PVAAT-2) (EC 2.6.1.1) was isolated from the common bean Phaseolus vulgaris nodule cDNA library. The nucleotide sequence analysis of the full-length cDNA allowed its identification by comparison with sequence databases. The amino acid sequence of the bean PvAAT-2 showed high similarity with the AAT-2 isoforms described in other leguminous plants. The amino-terminal region of the PvAAT-2 contains a sequence, which shares common features of plastid transit peptides. Southern blot analysis showed that the PvAAT-2 clone is encoded by a single gene in the P. vulgaris genome. Analysis of the PvAAT-2 mRNA levels suggests that the expression of this gene is nodule enhanced. The PvAAT-2 transcript is more abundant in nodules with increased synthesis of amides and is down-regulated in conditions where ureides accumulate. When plants were supplemented with ureides or with amides, PvAAT-2 expression was reduced, while it was not affected when plants were treated with allopurinol, an inhibitor of ureide synthesis. On the other hand, the expression of asparagine synthetase (another enzyme involved in the synthesis of amides) is not affected either by ureides or amides. These data suggest a role for AAT-2 in the mechanism involved in the synthesis of nitrogen compounds in bean nodules.