Laboratory of Plant Genetics, Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan.
J Integr Plant Biol. 2011 Dec;53(12):942-50. doi: 10.1111/j.1744-7909.2011.01083.x.
In the tetrapyrrole biosynthetic pathway of higher plants, 5-aminolevulinic acid (ALA) is metabolized by ALA dehydratase (ALAD). Here, we isolated ALAD1 cDNA from common wheat (Triticum aestivum L.) and its diploid progenitors, and produced transgenic tobacco plants expressing the wheat ALAD1 gene. The ALAD1 genes were highly conserved among wheat relatives, and three homoeologous loci of wheat ALAD1 (TaALAD1) were equally transcribed in common wheat. A transient expression assay of a TaALAD1-GFP (green fluorescent protein) fusion protein suggested that TaALAD1 is localized in chloroplasts. Overexpression of TaALAD1 in transgenic tobacco resulted in a significant increase in ALAD activity in leaves. Moreover, the transgenic tobacco showed vigorous growth and increased survival rate on medium containing ALA at herbicidal concentrations. These results indicate that wheat ALAD1 has catalytic activity in metabolizing ALA in plastids, and that ectopic expression of TaALAD1 in transgenic plants increases their tolerance to ALA application at high concentrations.
在高等植物的四吡咯生物合成途径中，5-氨基乙酰丙酸（ALA）由 ALA 脱水酶（ALAD）代谢。在这里，我们从普通小麦（Triticum aestivum L.）及其二倍体祖先中分离出 ALAD1 cDNA，并在烟草中表达了小麦 ALAD1 基因的转基因植物。小麦亲缘关系中的 ALAD1 基因高度保守，普通小麦中存在三个同源 TaALAD1（TaALAD1）基因位点，其转录水平相当。TaALAD1-GFP（绿色荧光蛋白）融合蛋白的瞬时表达试验表明，TaALAD1 定位于叶绿体中。在转基因烟草中超表达 TaALAD1 导致叶片中 ALAD 活性显著增加。此外，在含有除草浓度的 ALA 的培养基中，转基因烟草表现出旺盛的生长和增加的存活率。这些结果表明，小麦 ALAD1 在代谢质体中的 ALA 方面具有催化活性，并且 TaALAD1 在转基因植物中的异位表达增加了它们对高浓度 ALA 应用的耐受性。
