Loss of Cytosolic Phosphoglucose Isomerase Affects Carbohydrate Metabolism in Leaves and Is Essential for Fertility of Arabidopsis
Loss of Cytosolic Phosphoglucose Isomerase Affects Carbohydrate Metabolism in Leaves and Is Essential for Fertility of Arabidopsis
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DOI：
10.1104/pp.114.241091
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发表时间：
2014-10-01
期刊：
影响因子：
7.4
通讯作者：
Gierth, Markus
中科院分区：
文献类型：
--
作者：
Kunz, Hans-Henning;Zamani-Nour, Shirin;Gierth, Markus
植物的碳水化合物代谢与光合作用密切相关，是整个生物体能量和碳骨架供应的关键。因此，细胞质和叶绿体的己糖磷酸池代表重要的代谢资源，其通过磷酸葡萄糖异构酶（PGI）和磷酸葡萄糖异构酶相互转化葡萄糖6-磷酸、果糖6-磷酸和葡萄糖1-磷酸的作用来维持。在这里，我们研究了破坏细胞溶质PGI（cPGI）功能对植物生存力和代谢的影响。过表达靶向cPGI的人工微小RNA（amiR-cpgi）导致具有基本上不含cPGI活性的营养组织的成年植物。与野生型相比，这些植物表现出减少的生长，并且在叶绿体中积累了过量的淀粉，但在夜晚结束时保持了叶片中的低蔗糖含量。此外，amiR-cpgi植物表现出增加的非光化学叶绿素a猝灭在光合作用。与amiR-cpgi植物相反，cPGI功能被破坏的可行转移DNA插入突变体只能被鉴定为杂合个体。然而，在异位表达cPGI的植物中可以分离到纯合的转移DNA插入突变体。有趣的是，这些植物只有在由泛素10启动子驱动表达时才能生育，但在采用种子特异性未知种子蛋白启动子或花椰菜花叶病毒35 S启动子时是不育的。这些数据表明，代谢显然能够补偿成年amiR-cpgi植物中缺失的cPGI活性，并表明cPGI在植物繁殖中的基本功能。此外，我们的数据表明amiR-cpgi植物中的反馈调节，微调细胞质蔗糖代谢与质体淀粉周转。
Carbohydrate metabolism in plants is tightly linked to photosynthesis and is essential for energy and carbon skeleton supply of the entire organism. Thus, the hexose phosphate pools of the cytosol and the chloroplast represent important metabolic resources that are maintained through action of phosphoglucose isomerase (PGI) and phosphoglucose mutase interconverting glucose 6-phosphate, fructose 6-phosphate, and glucose 1-phosphate. Here, we investigated the impact of disrupted cytosolic PGI (cPGI) function on plant viability and metabolism. Overexpressing an artificial microRNA targeted against cPGI (amiR-cpgi) resulted in adult plants with vegetative tissue essentially free of cPGI activity. These plants displayed diminished growth compared with the wild type and accumulated excess starch in chloroplasts but maintained low sucrose content in leaves at the end of the night. Moreover, amiR-cpgi plants exhibited increased nonphotochemical chlorophyll a quenching during photosynthesis. In contrast to amiR-cpgi plants, viable transfer DNA insertion mutants disrupted in cPGI function could only be identified as heterozygous individuals. However, homozygous transfer DNA insertion mutants could be isolated among plants ectopically expressing cPGI. Intriguingly, these plants were only fertile when expression was driven by the ubiquitin10 promoter but sterile when the seed-specific unknown seed protein promoter or the Cauliflower mosaic virus 35S promoter were employed. These data show that metabolism is apparently able to compensate for missing cPGI activity in adult amiR-cpgi plants and indicate an essential function for cPGI in plant reproduction. Moreover, our data suggest a feedback regulation in amiR-cpgi plants that fine-tunes cytosolic sucrose metabolism with plastidic starch turnover.