MOLECULAR MECHANISMS ON THE REVERSIBLE MICROBODY TRANITION

在南瓜和拟南芥等肥苗的子叶中，在绿化过程中观察到微体从乙氧体向叶片过氧体的转变。在子叶的衰老过程中，从乙氧基体到叶过氧化物体的反向转换发生。已有的研究表明，糖氧体和叶片过氧化物体之间的功能转换在不同的水平上受到控制，如基因表达、蛋白质易位和蛋白质降解。遗传学方法可能是在分子水平上理解微体转变背后的调控机制(S)的有效策略。我们筛选了2，4-二氯苯氧基丁酸(2，4-DB)抗性突变体，这些突变体具有乙氧体功能缺陷。以前的研究表明，在高等植物中，2，4-二氯苯氧基丁酸(2，4-DB)是通过乙氧基体脂肪酸β氧化作用代谢产生除草剂的。为了分离乙氧基体脂肪酸β氧化缺陷的突变体，拟南芥…突变系在毒性水平2，4-DB存在的情况下，对更多的幼苗进行了生长筛选。其中12个突变株存活了下来，其中4个突变株萌发后生长需要蔗糖。这一结果表明，这些突变体在乙氧基体脂肪酸β氧化方面存在缺陷，因为乙氧基体脂肪酸β氧化在萌发过程中将蔗糖转化为贮藏脂肪具有重要作用。其中一个突变体缺乏硫解酶蛋白，这是一种参与种子萌发和随后的幼苗生长过程中脂肪酸β氧化的酶。另一个突变体在硫解酶从胞浆到乙氧基团的细胞内运输方面存在缺陷。两个突变体的黄化子叶都有形态异常的乙氧基体。在硫解酶缺陷突变体中，乙氧基体具有含有许多小泡的管状结构。通过对突变体的电子显微镜分析，研究了脂肪酸β氧化过程中乙氧基团与脂体的相互作用以及脂质从脂体到乙氧基团的运输。较少

In cotyledons of some fatty seedlings such as pumpkin and Arabidopsis, microbody transition from glyoxysomes to leaf peroxysomes is observed during greening. Reverse transition from glyoxysomes to leaf peroxisomes occurs during senescence of the cotyledons. It has been suggested that the functional conversion between glyoxysomes and leaf peroxisomes is controlled at various levels, such as gene expression, protein translocation and protein degradation. A genetically approach may be an effective strategy toward understanding the regulatory mechanism(s) underlying the microbody transition at the molecular level. We screened 2,4-dichIorophenoxybutyric acid (2,4-DB)-resistant mutants that have defects in glyoxysomal function.It has been previously demonstrated that 2,4-DB is metabolized to produce a herbicide, by the action of glyoxysomal fatty acid β-oxidation in higher plants. In order to isolate mutants that have defects in glyoxysomal fatty acid β-oxidation, mutant lines of Arabidopsis … More seedlings were screened for growth in the presence of toxic levels of 2,4-DB. Twelve of the mutants survived and of these, four required sucrose for post-germinative growth. This result suggests that these mutants have defects in glyoxysomal fatty acid β-oxidation, since glyoxysomal fatty acid β-oxidation has an important role in converting sucrose from storage lipids during germination. One of the mutants lacks thiolase protein, an enzyme involved in fatty acid β-oxidation during germination and subsequent seedling growth. Another mutant has a defect in the intracellular transport of thiolase form the cytosol to glyoxysomes. Etiolated cotyledons of both mutants have glyoxysomes with abnormal morphology. In the thiolase defective mutants, glyoxysomes have tubular structures that contain many vesicles. Interaction between glyoxysomes and lipid bodies and the transport of lipids from lipid bodies to glyoxysomes during fatty acid β-oxidation are studied by using the electron microscopic analysis of the mutants. Less