Cloning and characterization of deoxymugineic acid synthase genes from graminaceous plants
Cloning and characterization of deoxymugineic acid synthase genes from graminaceous plants
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DOI：
10.1074/jbc.m604133200
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发表时间：
2006-10-27
影响因子：
4.8
通讯作者：
Nishizawa, Naoko K.
中科院分区：
文献类型：
--
作者：
Bashir, Khurram;Inoue, Haruhiko;Nishizawa, Naoko K.
禾科植物已经进化出一种独特的机制，通过分泌一组小分子来获取铁，这些小分子被称为mumuineacid family phytosiderophores （MAs）。所有的MAs都是由L-Met合成的，从L-Met到2'-脱氧mugineic acid （DMA）具有相同的途径。DMA是通过脱氧镁酸合成酶（DMAS）还原3 ' ' -酮中间体合成的。我们从水稻（OsDMAS1）、大麦（HvDMAS1）、小麦（TaDMAS1）和玉米（ZmDMAS1）中分离到了DMAS基因。它们的核苷酸序列表明，OsDMAS1编码318个氨基酸的预测多肽，而其他三个同源物都编码314个氨基酸的预测多肽，并且彼此高度同源（82-97.5%）。DMAS蛋白属于醛酮还原酶超家族4 (AKR4)，但不属于AKR4现有的亚家族，似乎在AKR4群中构成了一个新的亚家族。所有蛋白在体外均表现出DMA合成活性。它们的酶活性在pH 8-9时最高，这与DMA是在亚细胞囊泡中合成的假设一致。Northern blot分析显示，缺铁条件下，根组织中上述DMAS基因表达均上调，茎组织中OsDMAS1和TaDMAS1基因表达上调。对缺铁根中OsDMAS1启动子- gus的分析表明，它的表达仅限于参与长距离运输的细胞，缺铁条件下，它在整个根中被高度上调。在茎部组织中，OsDMAS1启动子在缺铁条件下驱动维管束的表达。
Graminaceous plants have evolved a unique mechanism to acquire iron through the secretion of a family of small molecules, called mugineic acid family phytosiderophores (MAs). All MAs are synthesized from L-Met, sharing the same pathway from L-Met to 2'-deoxymugineic acid (DMA). DMA is synthesized through the reduction of a 3"-keto intermediate by deoxymugineic acid synthase ( DMAS). We have isolated DMAS genes from rice (OsDMAS1), barley (HvDMAS1), wheat (TaDMAS1), and maize (ZmDMAS1). Their nucleotide sequences indicate that OsDMAS1 encodes a predicted polypeptide of 318 amino acids, whereas the other three orthologs all encode predicted polypeptides of 314 amino acids and are highly homologous (82-97.5%) to each other. The DMAS proteins belong to the aldo-keto reductase superfamily 4 (AKR4) but do not fall within the existing subfamilies of AKR4 and appear to constitute a new subfamily within the AKR4 group. All of the proteins showed DMA synthesis activity in vitro. Their enzymatic activities were highest at pH 8-9, consistent with the hypothesis that DMA is synthesized in subcellular vesicles. Northern blot analysis revealed that the expression of each of the above DMAS genes is up-regulated under iron-deficient conditions in root tissue, and that of the genes OsDMAS1 and TaDMAS1 is up-regulated in shoot tissue. OsDMAS1 promoter-GUS analysis in iron-sufficient roots showed that its expression is restricted to cells participating in long distance transport and that it is highly up-regulated in the entire root under iron-deficient conditions. In shoot tissue, OsDMAS1 promoter drove expression in vascular bundles specifically under iron-deficient conditions.