Chloroplast localization of methylerythritol 4-phosphate pathway enzymes and regulation of mitochondrial genes in ispD and ispE albino mutants in Arabidopsis
Chloroplast localization of methylerythritol 4-phosphate pathway enzymes and regulation of mitochondrial genes in ispD and ispE albino mutants in Arabidopsis
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DOI：
10.1007/s11103-008-9297-5
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发表时间：
2008-04-01
影响因子：
5.1
通讯作者：
Chen, Ju-Jiun
中科院分区：
文献类型：
--
作者：
Hsieh, Ming-Hsiun;Chang, Chiung-Yun;Chen, Ju-Jiun
植物类异戊二烯来源于两个独立的途径，即胞质甲羟戊酸途径和质体甲基赤藓糖醇4-磷酸（MEP）途径。我们使用绿色荧光融合蛋白测定来证明拟南芥 MEP 途径酶定位于叶绿体。我们还鉴定了三种拟南芥白化突变体 ispD-1、ispD-2 和 ispE-1，它们在 MEP 途径的 IspD 和 IspE 基因中插入了 T-DNA。在这些白化突变体中，光合色素的水平几乎检测不到。 ispD 和 ispE 突变叶绿体充满了大囊泡，而不是类囊体。叶绿体发育和功能的受损可能预示着核、叶绿体和线粒体基因表达的变化。我们使用 Northern blot 分析来检查 ispD 和 ispE 白化突变体中光合和呼吸基因的表达。在白化突变体中，细胞核和叶绿体编码的光合基因的稳态 mRNA 水平显着降低。相反，在这些突变体中，编码线粒体电子传递链亚基的核基因和线粒体基因的转录水平增加或不受影响。基因组Southern印迹分析显示，ispD和ispE白化突变体中线粒体基因的DNA量没有增加。这些结果支持叶绿体的功能状态可能影响核和线粒体基因的表达的观点。白化突变体中线粒体基因的上调并不是由拟南芥中线粒体DNA拷贝数的变化引起的。
Plant isoprenoids are derived from two independent pathways, the cytosolic mevalonate pathway and the plastid methylerythritol 4-phosphate (MEP) pathway. We used green fluorescent fusion protein assays to demonstrate that the Arabidopsis MEP pathway enzymes are localized to the chloroplast. We have also characterized three Arabidopsis albino mutants, ispD-1, ispD-2 and ispE-1, which have T-DNA insertions in the IspD and IspE genes of the MEP pathway. Levels of photosynthetic pigments are almost undetectable in these albino mutants. Instead of thylakoids, the ispD and ispE mutant chloroplasts are filled with large vesicles. Impairments in chloroplast development and functions may signal changes in the expression of nuclear, chloroplast and mitochondrial genes. We used northern blot analysis to examine the expression of photosynthetic and respiratory genes in the ispD and ispE albino mutants. Steady-state mRNA levels of nucleus- and chloroplast-encoded photosynthetic genes are significantly decreased in the albino mutants. In contrast, transcript levels of nuclear and mitochondrial genes encoding subunits of the mitochondrial electron transport chain are increased or not affected in these mutants. Genomic Southern blot analysis revealed that the DNA amounts of mitochondrial genes are not enhanced in the ispD and ispE albino mutants. These results support the notion that the functional state of chloroplasts may affect the expression of nuclear and mitochondrial genes. The up-regulation of mitochondrial genes in the albino mutants is not caused by changes of mitochondrial DNA copy number in Arabidopsis.