Ezaki Bunichi, Suzuki Masakatsu, Motoda Hirotoshi, Kawamura Masako, Nakashima Susumu, Matsumoto Hideaki
Research Institute for Bioresources, Okayama University, 2-20-1, Chuou, Kurashiki, Okayama 710-0046, Japan.
Plant Physiol. 2004 Apr;134(4):1672-82. doi: 10.1104/pp.103.037135. Epub 2004 Mar 26.
The gene expression of two Al-induced Arabidopsis glutathione S-transferase genes, AtGST1 and AtGST11, was analyzed to investigate the mechanism underlying the response to Al stress. An approximately 1-kb DNA fragment of the 5'-upstream region of each gene was fused to a beta-glucuronidase (GUS) reporter gene (pAtGST1::GUS and pAtGST11::GUS) and introduced into Arabidopsis ecotype Landsberg erecta. The constructed transgenic lines showed a time-dependent gene expression to a different degree in the root and/or leaf by Al stress. The pAtGST1::GUS gene was induced after a short Al treatment (maximum expression after a 2-h exposure), while the pAtGST11::GUS gene was induced by a longer Al treatment (approximately 8 h for maximum expression). Since the gene expression was observed in the leaf when only the root was exposed to Al stress, a signaling system between the root and shoot was suggested in Al stress. A GUS staining experiment using an adult transgenic line carrying the pAtGST11::GUS gene supported this suggestion. Furthermore, Al treatment simultaneously with various Ca depleted conditions in root region enhanced the gene expression of the pAtGST11::GUS in the shoot region. This result suggested that the degree of Al toxicity in the root reflects the gene response of pAtGST11::GUS in the shoot via the deduced signaling system. Both transgenic lines also showed an increase of GUS activity after cold stress, heat stress, metal toxicity, and oxidative damages, suggesting a common induction mechanism in response to the tested stresses including Al stress.
为了研究拟南芥对铝胁迫响应的潜在机制，分析了两个铝诱导的谷胱甘肽S-转移酶基因AtGST1和AtGST11的基因表达。将每个基因5'上游区域约1 kb的DNA片段与β-葡萄糖醛酸酶（GUS）报告基因融合（pAtGST1::GUS和pAtGST11::GUS），并导入拟南芥生态型Landsberg erecta。构建的转基因株系在铝胁迫下，根和/或叶中呈现出不同程度的时间依赖性基因表达。pAtGST1::GUS基因在短时间铝处理后被诱导（2小时暴露后达到最大表达），而pAtGST11::GUS基因在较长时间铝处理后被诱导（约8小时达到最大表达）。由于仅根部暴露于铝胁迫时在叶中观察到基因表达，因此推测在铝胁迫下根和地上部之间存在信号传导系统。使用携带pAtGST11::GUS基因的成年转基因株系进行的GUS染色实验支持了这一推测。此外，在根区域同时用各种缺钙条件处理铝，增强了地上部区域pAtGST11::GUS的基因表达。该结果表明，根中铝毒性的程度通过推测的信号传导系统反映了地上部pAtGST11::GUS的基因反应。两个转基因株系在冷胁迫、热胁迫、金属毒性和氧化损伤后也显示出GUS活性增加，表明对包括铝胁迫在内的测试胁迫存在共同的诱导机制。
