College of Life Sciences, Cooperative Demonstration Laboratory of Centrifuge Technique, Nanjing Agricultural University and Beckman Coulter Ltd Co., Nanjing Agricultural University, Nanjing 210095, China.
J Exp Bot. 2011 Aug;62(13):4675-89. doi: 10.1093/jxb/err190. Epub 2011 Jun 14.
In this report, a rapeseed (Brassica napus) haem oxygenase-1 gene BnHO1 was cloned and sequenced. It shared high homology with Arabidopsis HY1 proteins, and encodes a 32.6 kDa protein with a 54-amino-acid transit peptide, predicting the mature protein of 25.1 kDa. The mature BnHO1 expressed in Escherichia coli exhibits haem oxygenase (HO) activity. Furthermore, the application of lower doses of NaCl (10 mM) and polyethylene glycol (PEG) (2%) mimicked the inducible effects of naphthylacetic acid and the HO-1 inducer haemin on the up-regulation of BnHO1 and subsequent lateral root (LR) formation. Contrasting effects were observed when a higher dose of NaCl or PEG was applied. The above inducible and inhibitory responses were blocked significantly when the HO-1 inhibitor zinc protoporphyrin IX (ZnPPIX) or haemin was applied, both of which were reversed by the application of carbon monoxide or ZnPPIX, respectively. Moreover, the addition of ZnPPIX at different time points during LR formation indicated that BnHO1 might be involved in the early stages of LR formation. The auxin response factor transcripts and the auxin content in seedling roots were clearly induced by lower doses of salinity or osmotic stress. However, treatment with the inhibitor of polar auxin transport N-1-naphthylphthalamic acid prevented the above inducible responses conferred by lower doses of NaCl and PEG, which were further rescued when the treatments were combined with haemin. Taken together, these results suggested a novel role of the rapeseed HO-1 gene in salinity and osmotic stress-induced LR formation, with a possible interaction with auxin signalling.
本报告克隆并测序了油菜（Brassica napus）血红素加氧酶-1 基因 BnHO1。它与拟南芥 HY1 蛋白具有高度同源性，编码一个 32.6 kDa 的蛋白，带有 54 个氨基酸的转运肽，预测成熟蛋白为 25.1 kDa。在大肠杆菌中表达的成熟 BnHO1 表现出血红素加氧酶（HO）活性。此外，较低剂量的 NaCl（10 mM）和聚乙二醇（PEG）（2%）模拟了萘乙酸和 HO-1 诱导剂血红素对 BnHO1 上调和随后侧根（LR）形成的诱导作用。当应用较高剂量的 NaCl 或 PEG 时，观察到相反的效果。当应用 HO-1 抑制剂锌原卟啉 IX（ZnPPIX）或血红素时，上述诱导和抑制反应被显著阻断，分别用一氧化碳或 ZnPPIX 处理可逆转。此外，在 LR 形成过程中不同时间点添加 ZnPPIX 表明 BnHO1 可能参与 LR 形成的早期阶段。在幼苗根中，生长素反应因子转录本和生长素含量明显受到低盐或渗透胁迫的诱导。然而，用生长素极性运输抑制剂 N-1-萘基邻氨甲酰苯甲酸处理阻止了 NaCl 和 PEG 低剂量诱导的上述反应，当将这些处理与血红素联合处理时，这些反应得到了挽救。综上所述，这些结果表明油菜 HO-1 基因在盐度和渗透胁迫诱导的 LR 形成中发挥了新的作用，可能与生长素信号转导相互作用。
