Export of Vacuolar Manganese by AtNRAMP3 and AtNRAMP4 Is Required for Optimal Photosynthesis and Growth under Manganese Deficiency
Export of Vacuolar Manganese by AtNRAMP3 and AtNRAMP4 Is Required for Optimal Photosynthesis and Growth under Manganese Deficiency
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DOI：
10.1104/pp.109.150946
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发表时间：
2010-04-01
期刊：
影响因子：
7.4
通讯作者：
Thomine, Sebastien
中科院分区：
文献类型：
--
作者：
Lanquar, Viviane;Ramos, Magali Schnell;Thomine, Sebastien
锰（Mn）是一种必需元素，在许多酶中起辅因子的作用。特别是，Mn簇是光系统II的放氧复合物的功能不可缺少的。天然抗性相关巨噬细胞蛋白（NRAMP）家族的金属转运蛋白具有转运铁和锰的能力。AtNRAMP 3和AtNRAMP 4是萌发种子中铁动员所必需的。本文报道的结果表明，在成年拟南芥（Arabidopsis thaliana）植物中，AtNRAMP 3和AtNRAMP 4在Mn稳态中具有重要作用。与野生型相比，nramp 3 nramp 4双突变体植株莲座叶叶肉细胞中的锰累积量显著增加。这表明，相当大比例的细胞锰池通过液泡，并在AtNRAMP 3/AtNRAMP 4依赖的方式检索。从叶肉液泡的nramp 3 nramp 4双突变体植物的锰释放受损与锰缺乏下的生长减少。然而，叶AtNRAMP 3和AtNRAMP 4蛋白水平不受锰供应的影响。在Mn缺乏的情况下，nramp 3 nramp 4植物含有比野生型少的功能性光系统II。这些数据是一致的锰短缺产生功能性光系统II，而线粒体锰依赖性超氧化物歧化酶活性维持在锰缺乏症在两种基因型。这里提出的结果表明，一个重要的作用AtNRAMP 3/AtNRAMP 4依赖锰运输通过液泡进口到叶绿体的叶肉细胞。
Manganese (Mn) is an essential element, acting as cofactor in numerous enzymes. In particular, a Mn cluster is indispensable for the function of the oxygen-evolving complex of photosystem II. Metal transporters of the Natural Resistance-Associated Macrophage Protein (NRAMP) family have the ability to transport both iron and Mn. AtNRAMP3 and AtNRAMP4 are required for iron mobilization in germinating seeds. The results reported here show that, in adult Arabidopsis (Arabidopsis thaliana) plants, AtNRAMP3 and AtNRAMP4 have an important role in Mn homeostasis. Vacuolar Mn accumulation in mesophyll cells of rosette leaves of adult nramp3nramp4 double mutant plants was dramatically increased when compared with the wild type. This suggests that a considerable proportion of the cellular Mn pool passes through the vacuole and is retrieved in an AtNRAMP3/AtNRAMP4-dependent manner. The impaired Mn release from mesophyll vacuoles of nramp3nramp4 double mutant plants is associated with reduced growth under Mn deficiency. However, leaf AtNRAMP3 and AtNRAMP4 protein levels are unaffected by Mn supply. Under Mn deficiency, nramp3nramp4 plants contain less functional photosystem II than the wild type. These data are consistent with a shortage of Mn to produce functional photosystem II, whereas mitochondrial Mn-dependent superoxide dismutase activity is maintained under Mn deficiency in both genotypes. The results presented here suggest an important role for AtNRAMP3/AtNRAMP4-dependent Mn transit through the vacuole prior to the import into chloroplasts of mesophyll cells.