Henriquez Maria Antonia, Soliman Atta, Li Genyi, Hannoufa Abdelali, Ayele Belay T, Daayf Fouad
Department of Plant Science, University of Manitoba, 222 Agriculture Building, Winnipeg, MB R3T2N2, Canada; Agriculture and Agri-Food Canada, Morden, MB, Canada.
Department of Plant Science, University of Manitoba, 222 Agriculture Building, Winnipeg, MB R3T2N2, Canada; Department of Genetics, Faculty of Agriculture, University of Tanta, Tanta, El-Gharbia, Egypt.
Plant Sci. 2016 Feb;243:71-83. doi: 10.1016/j.plantsci.2015.12.001. Epub 2015 Dec 3.
1-Deoxy-D-xylulose 5-phosphate synthase (DXS) catalyzes the initial step of the plastidial 2C-methyl-D-erythritol-4-phosphate (DOXP-MEP) pathway involved in isoprenoid biosynthesis. In this study, we cloned the complete cDNA of potato DXS gene that was designated StDXS1. StDXS1 cDNA encodes for 719 amino acid residues, with MW of 77.8 kDa, and is present in one copy in the potato genome. Phylogenetic analysis and protein sequence alignments assigned StDXS1 to a group with DXS homologues from closely related species and exhibited homodomain identity with known DXS proteins from other plant species. Late blight symptoms occurred in parallel with a reduction in StDXS1 transcript levels, which may be associated with the levels of isoprenoids that contribute to plant protection against pathogens. Subcellular localization indicated that StDXS1 targets the chloroplasts where isoprenoids are synthesized. Arabidopsis expressing StDXS1 showed a higher accumulation of carotenoids and chlorophyll as compared to wild type controls. Lower levels of ABA and GA were detected in the transgenic DXS lines as compared to control plants, which reflected on higher germination rates of the transgenic DXS lines. No changes were detected in JA or SA contents. Selected downstream genes in the DOXP-MEP pathway, especially GGPPS genes, were up-regulated in the transgenic lines.
1-脱氧-D-木酮糖-5-磷酸合酶（DXS）催化参与类异戊二烯生物合成的质体2C-甲基-D-赤藓糖醇-4-磷酸（DOXP-MEP）途径的起始步骤。在本研究中，我们克隆了马铃薯DXS基因的完整cDNA，命名为StDXS1。StDXS1 cDNA编码719个氨基酸残基，分子量为77.8 kDa，在马铃薯基因组中以单拷贝形式存在。系统发育分析和蛋白质序列比对将StDXS1归为与近缘物种的DXS同源物同一类群，并与其他植物物种的已知DXS蛋白表现出同源结构域一致性。晚疫病症状与StDXS1转录水平的降低同时出现，这可能与有助于植物抵御病原体的类异戊二烯水平有关。亚细胞定位表明StDXS1定位于类异戊二烯合成的叶绿体。与野生型对照相比，表达StDXS1的拟南芥显示出更高的类胡萝卜素和叶绿素积累。与对照植物相比，转基因DXS系中检测到较低水平的脱落酸（ABA）和赤霉素（GA），这反映在转基因DXS系的更高发芽率上。茉莉酸（JA）或水杨酸（SA）含量未检测到变化。DOXP-MEP途径中选定的下游基因，尤其是牻牛儿基牻牛儿基焦磷酸合酶（GGPPS）基因，在转基因系中上调。
