Molecular mechanisms of the microbody transition in higher plants

为了阐明高等植物的微体转变，我们分析了脂肪酸氧化缺陷的微体膜蛋白和拟南芥突变体的发育。我们对主要的微体膜蛋白之一PMP38进行了表征。拟南芥cDNA的氨基酸序列包含331个氨基酸，与人类PMP34和假丝酵母PMP47线粒体ATP/ADP载体蛋白同源物具有较高的相似性。南瓜子叶的细胞分离和免疫细胞化学分析表明，PMP38作为一种完整的膜蛋白定位在微体膜上。南瓜子叶中PMP38的含量在黑暗处理6 d后增加，达到最高蛋白水平，随后下降。这些结果清楚地表明，在glyoxysomal转化为叶片过氧化物酶体的过程中，glyoxysomal膜蛋白PMP38发生了更大的数学变化，其他glyoxysomal酶，特别是脂肪酸-氧化循环的酶，定位于glyoxysomal基质中。我们之前通过对2,4 -二氯苯氧基丁酸的抗性分离出一个拟南芥过氧化物酶体缺陷ped2突变体。我们描述了一个基因负责这种缺陷的分离，称为PED2基因，通过定位克隆和互补分析证实了它的身份。预测蛋白产物的氨基酸序列与人类的Pex14p相似，Pex14p是微体蛋白进口机制的关键组成部分。因此，我们决定将其命名为AtPex14p。对ped2突变体的分析表明，AtPex14p控制过氧化物酶体靶向信号（PTS）1和含有pts2的蛋白在细胞内转运到三种不同类型的微体，即乙氧基小体、叶片过氧化物酶体和非特化过氧化物酶体。PED2基因的突变导致所有这些功能分化微体中酶的减少。这些酶的减少引起多效性缺陷，如脂肪酸降解、光呼吸和微体的形态。我们还鉴定出PED3基因是一个全尺寸的atp结合盒转运体。目前对这些突变体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