Reversibility of peroxisomal differentiation in higher plants.

高等植物细胞中的过氧化物体根据细胞类型的不同而在功能上发生分化。通过对拟南芥全基因组中的过氧化物体基因的全面调查，我们发现了286个候选的过氧化物体基因。它们包含了迄今为止报道的所有过氧化物体酶的基因，其中大多数编码了过氧化物体中功能未知的蛋白质。基因表达谱分析表明，过氧化体分化是由特定器官中诱导的特定基因的表达以及结构性表达的基因引起的。聚类分析表明，过氧化物酶的基本功能是β氧化、H_2O_2降解、支链氨基酸分解代谢和一些未知功能，幼苗、子叶、叶片和根中的过氧化物酶是通过器官特异表达基因来区分的，其中一个突变体apm1的过氧化物体较长，数量减少，明显是由于分裂受到抑制。我们发现APM1编码DRP3A(动力素相关蛋白3A)，APM1/DRP3A的突变也导致线粒体形态异常。瞬时表达分析表明，DRP3A与过氧化物体的胞浆糖苷有关。通过对依赖PTS1途径转运蛋白质的apm2和apm4突变体的分析，我们确定了APM2和APM4基因分别编码PEROXIN13(PEX13)和PEX12，并揭示了它们与过氧化体膜上的pts2和PTS1依赖的蛋白有关。

Peroxisomes in higher plantcells are known to differentiate in function depending on the cell type. By a comprehensive survey of peroxisomal genes in the entire Arabidopsis genome, we found 286 candidates of peroxisomal genes. They included all genes for peroxisomal enzymes reported up to date, and most of them encoded functionally unknown proteins in peroxisomes. Analyses of gene expression profiles revealed that peroxisomal differentiation is caused by the expression of specific genes that are induced in specific organs in addition to constitutively expressed genes. The clustering analyses suggested that basic functions of peroxisomewereβ-oxidation, H_2O_2 degradation, branched chain amino acid catabolism and some unknown functions, and that peroxisomesinseedlings, cotyledons, leavesand roots were differentiated by organ-specific expressed genes.In one of these mutants, apm1, the peroxisomes are long and reduced in number, apparently as a result of inhibition of division. We showed that APM1 encodes DRP3A (dynamin-related protein 3A), and that mutations in APM1/DRP3A also caused aberrant morphology of mitochondria. The transient expression analysis showed that DRP3A is associated with the cytosolicsideofperoxisomes. Thesesfindingsindicate that the same dynamin molecule is involved in peroxisomal and mitochondrialdivision in higherplants.From analyses of apm2 and apm4 mutants which are difectiveinproteintransportbyPTS1-dependent pathway, we determined that APM2 and APM4 genes encode PEROXIN13 (PEX13) and PEX12, respectively, and revealed that they are responsible for PTS2-as well as PTS1-dependent protein on the peroxisomal membrane.