Department of Biochemistry and Molecular Biology, College of Life Science, Nanjing Agricultural University, Nanjing 210095, China.
Plant Cell Environ. 2011 May;34(5):752-63. doi: 10.1111/j.1365-3040.2011.02279.x. Epub 2011 Feb 25.
Plant heme oxygenases (HOs) regulate biosynthesis of phytochrome which accounts for photo-acceptance and -morphogenesis. Recent studies have demonstrated that plant HOs also regulate many other physiological processes including response to environmental stimuli. To elucidate the mechanism by which HOs regulate plant adaptation to heavy metal exposure, three novel HOs genes were isolated from rapeseed (Brassica napus) and their expression patterns were analysed. Alignment of deduced protein sequences revealed that the three BnHOs share high identity with their corresponding orthologos (AtHO1-3) from Arabidopsis. To investigate whether the BnHO regulates plant tolerance to Hg toxicity, we constructed B. napus transgenic plants overexpressing BnHO-1. Under Hg stress, the transgenic plants had 1.41-1.59 folds higher biomass than the untransformants. However, overexpression of BnHO-1 resulted in less accumulation of Hg in some lines of transformants than in untransformants. The transgenic plants show lower abundance of reactive oxygen species and attenuated oxidative injury compared with the untransgenic plants. We cloned the promoter sequences of BnHO-1 from B. napus. Analysis revealed that the 1119 bp fragment contains a conserved Cd responsive element (CdRE) and others responding to multiple environmental stimuli. Transient expression in tobacco leaves showed differential responses to heavy metals (Zn, Cu, Pb, Hg and Cd).
植物血红素加氧酶（HOs）调节植物光敏素的生物合成，而光敏素则负责光的接受和形态发生。最近的研究表明，植物 HOs 还调节许多其他生理过程，包括对环境刺激的反应。为了阐明 HOs 调节植物适应重金属暴露的机制，从油菜（Brassica napus）中分离出三个新的 HOs 基因，并分析了它们的表达模式。推导的蛋白质序列比对表明，这三个 BnHOs 与拟南芥的相应同源物（AtHO1-3）具有高度的同一性。为了研究 BnHO 是否调节植物对 Hg 毒性的耐受性，我们构建了油菜过表达 BnHO-1 的转基因植物。在 Hg 胁迫下，转基因植物的生物量比非转化体高 1.41-1.59 倍。然而，在一些转基因植物中，BnHO-1 的过表达导致 Hg 的积累比非转化体少。与非转基因植物相比，转基因植物表现出较低的活性氧含量和减轻的氧化损伤。我们从油菜中克隆了 BnHO-1 的启动子序列。分析表明，1119bp 片段含有一个保守的 Cd 响应元件（CdRE）和其他响应多种环境刺激的元件。在烟草叶片中的瞬时表达显示出对重金属（Zn、Cu、Pb、Hg 和 Cd）的不同反应。
