Ji Chang Yoon, Kim Yun-Hee, Kim Ho Soo, Ke Qingbo, Kim Gun-Woo, Park Sung-Chul, Lee Haeng-Soon, Jeong Jae Cheol, Kwak Sang-Soo
Plant Systems Engineering Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), 125 Gwahak-ro, Daejeon 34141, South Korea; Department of Green Chemistry and Environmental Biotechnology, Korea University of Science and Technology (UST), 217 Gajeong-ro, Daejeon 34113, South Korea.
Department of Biology Education, College of Education, IALS, Gyeongsang National University, 501 Jinju-Daero, Jinju 52828, South Korea.
Plant Physiol Biochem. 2016 Sep;106:118-28. doi: 10.1016/j.plaphy.2016.04.037. Epub 2016 Apr 20.
Tocopherol (vitamin E) is a chloroplast lipid that is presumed to be involved in the plant response to oxidative stress. In this study, we isolated and characterized five tocopherol biosynthetic genes from sweetpotato (Ipomoea batatas [L.] Lam) plants, including genes encoding 4-hydroxyphenylpyruvate dioxygenase (IbHPPD), homogentisate phytyltransferase (IbHPT), 2-methyl-6-phytylbenzoquinol methyltransferase (IbMPBQ MT), tocopherol cyclase (IbTC) and γ-tocopherol methyltransferase (IbTMT). Fluorescence microscope analysis indicated that four proteins localized into the chloroplast, whereas IbHPPD observed in the nuclear. Quantitative RT-PCR analysis revealed that the expression patterns of the five tocopherol biosynthetic genes varied in different plant tissues and under different stress conditions. All five genes were highly expressed in leaf tissues, whereas IbHPPD and IbHPT were highly expressed in the thick roots. The expression patterns of these five genes significantly differed in response to PEG, NaCl and H2O2-mediated oxidative stress. IbHPPD was strongly induced following PEG and H2O2 treatment and IbHPT was strongly induced following PEG treatment, whereas IbMPBQ MT and IbTC were highly expressed following NaCl treatment. Upon infection of the bacterial pathogen Pectobacterium chrysanthemi, the expression of IbHPPD increased sharply in sweetpotato leaves, whereas the expression of the other genes was reduced or unchanged. Additionally, transient expression of the five tocopherol biosynthetic genes in tobacco (Nicotiana bentamiana) leaves resulted in increased transcript levels of the transgenes expressions and tocopherol production. Therefore, our results suggested that the five tocopherol biosynthetic genes of sweetpotato play roles in the stress defense response as transcriptional regulators of the tocopherol production.
生育酚（维生素E）是一种叶绿体脂质，被认为参与植物对氧化应激的反应。在本研究中，我们从甘薯（Ipomoea batatas [L.] Lam）植株中分离并鉴定了五个生育酚生物合成基因，包括编码4-羟基苯丙酮酸双加氧酶（IbHPPD）、尿黑酸植基转移酶（IbHPT）、2-甲基-6-植基苯醌甲基转移酶（IbMPBQ MT）、生育酚环化酶（IbTC）和γ-生育酚甲基转移酶（IbTMT）的基因。荧光显微镜分析表明，四种蛋白质定位于叶绿体中，而IbHPPD在细胞核中被观察到。定量RT-PCR分析显示，五个生育酚生物合成基因的表达模式在不同植物组织和不同胁迫条件下有所不同。所有五个基因在叶片组织中高度表达，而IbHPPD和IbHPT在粗根中高度表达。这五个基因的表达模式在响应聚乙二醇（PEG）、氯化钠（NaCl）和过氧化氢（H2O2）介导的氧化应激时存在显著差异。PEG和H2O2处理后，IbHPPD被强烈诱导，PEG处理后，IbHPT被强烈诱导，而NaCl处理后，IbMPBQ MT和IbTC高度表达。在被细菌病原体菊欧文氏菌感染后，甘薯叶片中IbHPPD的表达急剧增加，而其他基因的表达则降低或不变。此外，五个生育酚生物合成基因在烟草（Nicotiana bentamiana）叶片中的瞬时表达导致转基因表达的转录水平和生育酚产量增加。因此，我们的结果表明，甘薯的五个生育酚生物合成基因作为生育酚产生的转录调节因子，在胁迫防御反应中发挥作用。
