Recent work revealed that PGD2, an Arabidopsis 6-phosphogluconate dehydrogenase (6-PGD) catalysing the third step of the oxidative pentose-phosphate pathway (OPPP) in peroxisomes, is essential during fertilization. Earlier studies on the second step, catalysed by PGL3, a dually targeted Arabidopsis 6-phosphogluconolactonase (6-PGL), reported the importance of OPPP reactions in plastids but their irrelevance in peroxisomes. Assuming redundancy of 6-PGL activity in peroxisomes, we examined the sequences of other higher plant enzymes. In tomato, there exist two 6-PGL isoforms with the strong PTS1 motif SKL. However, their analysis revealed problems regarding peroxisomal targeting: reporter-PGL detection in peroxisomes required construct modification, which was also applied to the Arabidopsis isoforms. The relative contribution of PGL3 versus PGL5 during fertilization was assessed by mutant crosses. Reduced transmission ratios were found for pgl3-1 (T-DNA-eliminated PTS1) and also for knock-out allele pgl5-2. The prominent role of PGL3 showed as compromised growth of pgl3-1 seedlings on sucrose and higher activity of mutant PGL3-1 versus PGL5 using purified recombinant proteins. Evidence for PTS1-independent uptake was found for PGL3-1 and other Arabidopsis PGL isoforms, indicating that peroxisome import may be supported by a piggybacking mechanism. Thus, multiple redundancy at the level of the second OPPP step in peroxisomes explains the occurrence of pgl3-1 mutant plants.

中文翻译：

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过氧化物酶体中拟南芥6-磷酸葡萄糖酸内酯酶同工型之间的潜在冗余分析。

最近的工作表明，PGD2是一种拟南芥属的6-磷酸葡萄糖酸脱氢酶（6-PGD），在过氧化物酶体中催化氧化戊糖-磷酸途径（OPPP）的第三步，在受精过程中至关重要。在第二步的较早研究中，由PGL3（一种双重靶向的拟南芥6-磷酸葡萄糖酸内酰胺酶（6-PGL））催化，报道了OPPP反应在质体中的重要性，但在过氧化物酶体中却无关紧要。假设过氧化物酶体中6-PGL活性存在冗余，我们检查了其他高等植物酶的序列。在番茄中，存在两个带有强PTS1基序SKL的6-PGL亚型。但是，他们的分析揭示了过氧化物酶体靶向的问题：过氧化物酶体中的报告基因PGL检测需要对构建体进行修饰，这也适用于拟南芥同工型。通过突变杂交评估受精过程中PGL3与PGL5的相对贡献。发现pgl3-1（消除T-DNA的PTS1）和敲除的等位基因pgl5-2的传输率均降低。PGL3的突出作用表现为pgl3-1幼苗在蔗糖上的生长受到损害，并且突变PGL3-1与使用纯化的重组蛋白的PGL5相比具有更高的活性。已发现PGL3-1和其他拟南芥PGL同工型的PTS1独立摄取的证据，表明过氧化物酶体的输入可能受mechanism带机制的支持。因此，过氧化物酶体中第二个OPPP步骤水平的多重冗余解释了pgl3-1突变植物的出现。PGL3的突出作用表现为pgl3-1幼苗在蔗糖上的生长受到损害，并且突变PGL3-1与使用纯化的重组蛋白的PGL5相比具有更高的活性。已发现PGL3-1和其他拟南芥PGL同工型的PTS1独立摄取的证据，表明过氧化物酶体的输入可能受mechanism带机制的支持。因此，过氧化物酶体中第二个OPPP步骤水平的多重冗余解释了pgl3-1突变植物的出现。PGL3的突出作用表现为pgl3-1幼苗在蔗糖上的生长受到损害，并且突变PGL3-1与使用纯化的重组蛋白的PGL5相比具有更高的活性。已发现PGL3-1和其他拟南芥PGL同工型的PTS1独立摄取的证据，表明过氧化物酶体的输入可能受mechanism带机制的支持。因此，过氧化物酶体中第二个OPPP步骤水平的多重冗余解释了pgl3-1突变植物的出现。