Molecular mechanisms of the microbody transition in higher plants

为了阐明微体在高等植物中的转变，我们分析了微体膜蛋白和脂肪酸 *-氧化缺陷的拟南芥突变体的发育。我们的主要微体膜蛋白，PMP 38的特点之一。该蛋白在拟南芥中的cDNA序列与已知的线粒体ATP/ADP载体蛋白同源物Homosapiens PMP 34和Candidaboidinll PMP 47的氨基酸序列具有高度的相似性。利用南瓜子叶进行的细胞分级分离和免疫细胞化学分析表明，PMP 38作为一个完整的膜蛋白定位在微体膜上。南瓜子叶中PMP 38的含量在黑暗条件下逐渐增加，6 d后达到最大值，此后下降。这些结果清楚地表明，乙醛酸酶体中的膜蛋白PMP 38的含量随着光照时间的延长而增加。 ...更多信息 在乙醛酸酶体转化为叶过氧化物酶体的过程中，这些酶被激活，就像其他乙醛酸酶体酶，特别是位于乙醛酸酶体基质中的脂肪酸 *-氧化循环的酶一样。我们先前分离了一个拟南芥过氧化物酶体缺陷型ped 2突变体，它对2，4-二氯苯氧基丁酸具有抗性。我们描述了分离的基因负责这种缺陷，称为PED 2基因，通过定位克隆，并确认其身份的互补分析。预测的蛋白质产物的氨基酸序列与人Pex 14 p的氨基酸序列相似，Pex 14 p是微体蛋白质输入机制的关键组分。因此，我们决定将其命名为AtPex 14 p。ped 2突变体的分析表明，AtPex 14 p控制细胞内运输的过氧化物酶体靶向信号（PTS）1和含PTS 2的蛋白质进入三种不同类型的微体，即乙醛酸酶体，叶过氧化物酶体和非特异性过氧化物酶体。PED 2基因的突变导致所有这些功能分化的微体中的酶减少。这些酶的减少诱导多效性缺陷，例如脂肪酸降解、光呼吸和微体的形态。我们还确定了PED 3基因作为一个完整的大小ATP结合盒转运。对这些突变体中微体转变的研究正在进行中。少

In order to clarify the microbody transition in higher plants, we have analyzed the development of microbody membrane proteins and arabidopsis mutants that defects on fatty acid *** -oxidation. We characterized one of the major microbody membrane proteins, PMP38. The deduced amino acid sequence for its cDNA in Arabidopsis thalia na contained polypeptides with 331 amino acids and had high similarity with those of Homo sapiens PMP34 and Candida boidinll PMP47 known as homologues of mitochondrial ATP/ADP carrier protein. Cell fractionation and immunocytochemical analysis using pumpkin cotyledons revealed that PMP38 is localized on microbody membranes as an integralmembrane protein. The amount of PMP38 in pumpkin cotyledons increased and reached the maximum protein level after 6 d in the dark but decreased thereafter. Illumination of the seedlings caused a significant decrease in the amount of the proteinThese results clearly showed that themembrane protein PMP38 in glyoxysomes changes dra … More matically during the transformation of glyoxysomes to leaf peroxisomes, as do the other glyoxysomal enzymes, especially enzymes of the fatty acid *** -oxidation cycle, that are localized in the matrix of glyoxysomes. We previously isolated an Arabidopsis peroxisomedeficient ped2 mutant by its resistance to 2, 4-dichlorophenoxybutyric acid. We describe the isolation of a gene responsible for this deficiency, called the PED2 gene, by positional cloning and confirmed its identity by complementation analysis. The amino acid sequence of the predicted protein product is similar to that of human Pex14p, which is a key component of the microbody protein import machinery. Therefore, we decided to call it AtPex14p. Analyzes of the ped2 mutant revealed that AtPex14p controls intracellular transport of both peroxisome targeting signal (PTS)1 and PTS2-containing proteins into three different types of microbodies, namely glyoxysomes, leaf peroxisomes and unspecialized peroxisomes. Mutation in the PED2 gene results in reduction of enzymes in all of these functionally differentiated microbodies. The reduction in these enzymes induces pleiotropic defects, such as fatty acid degradation, photorespiration and the morphology of microbodies. We also identified PED3 gene as a full-size ATP-binding cassette transporter. The studies on the microbody transition in these mutants are now in progress. Less