Analysis of potential redundancy among Arabidopsis 6-phosphogluconolactonase isoforms in peroxisomes
Analysis of potential redundancy among Arabidopsis 6-phosphogluconolactonase isoforms in peroxisomes
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DOI：
10.1093/jxb/erz473
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发表时间：
2020-01-23
影响因子：
6.9
通讯作者：
von Schaewen, Antje
中科院分区：
文献类型：
--
作者：
Lansing, Hannes;Doering, Lennart;von Schaewen, Antje
最近的研究表明，PGD 2，拟南芥6-磷酸葡萄糖酸脱氢酶（6-PGD）催化过氧化物酶体中的氧化戊糖-磷酸途径（OPPP）的第三步，在受精过程中是必不可少的。早期关于第二步的研究报道了OPPP反应在质体中的重要性，但它们在过氧化物酶体中不相关，第二步由PGL 3催化，PGL 3是一种双重靶向的拟南芥6-磷酸肌醇内酯酶（6-PGL）。假设过氧化物酶体中6-PGL活性冗余，我们检查了其他高等植物酶的序列。在番茄中，存在两种具有强PTS 1基序SKL的6-PGL异构体。然而，他们的分析揭示了关于过氧化物酶体靶向的问题：过氧化物酶体中的p-PGL检测需要构建体修饰，这也适用于拟南芥同种型。通过突变体杂交来评估PGL 3与PGL 5在受精期间的相对贡献。发现pgl 3 -1（T-DNA消除的PTS 1）和敲除等位基因pgl 5 -2的传递率降低。PGL 3的突出作用表现为pgl 3 -1幼苗在蔗糖上的受损生长以及使用纯化的重组蛋白的突变体PGL 3 -1相对于PGL 5的更高活性。PTS 1-独立的摄取的证据被发现的PGL 3 -1和其他拟南芥PGL亚型，表明过氧化物酶体进口可能支持的捎带机制。因此，过氧化物酶体中第二个OPPP步骤水平上的多重冗余解释了pgl 3 -1突变体植物的发生。
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.