Chloroplast Fe(III) chelate reductase activity is essential for seedling viability under iron limiting conditions
Chloroplast Fe(III) chelate reductase activity is essential for seedling viability under iron limiting conditions
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DOI：
10.1073/pnas.0708367105
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发表时间：
2008-07-29
影响因子：
11.1
通讯作者：
Guerinot, Mary Lou
中科院分区：
文献类型：
--
作者：
Jeong, Jeeyon;Cohu, Christopher;Guerinot, Mary Lou
光合作用、血红素生物合成和铁-S簇组装都发生在叶绿体中，都需要铁。在各种系统中，在铁跨膜运输之前，需要通过膜结合的Fe(III)螯合还原酶来还原铁，但到目前为止，还没有明确的遗传证据证明叶绿体有这样的还原系统。在这里，我们报道了拟南芥铁还原酶氧化酶(FRO)家族的8个成员之一，FRO7，定位于叶绿体。从7个功能缺失突变体制备的叶绿体比野生型叶绿体的Fe(III)螯合还原酶活性低75%，每微克叶绿体含铁量少33%。这种铁含量的降低可能是光合作用电子传递缺陷的原因。当在碱性土壤中萌发时，FRO7幼苗表现出严重的黄化，除非用高水平的可溶性铁浇水，否则不会结籽而死亡。总体而言，我们的结果提供了FR07在叶绿体铁获取中发挥作用的分子证据，是幼苗高效光合作用和铁限制条件下生存所必需的。
Photosynthesis, heme biosynthesis, and Fe-S cluster assembly all take place in the chloroplast, and all require iron. Reduction of iron via a membrane-bound Fe(III) chelate reductase is required before iron transport across membranes in a variety of systems, but to date there has been no definitive genetic proof that chloroplasts have such a reduction system. Here we report that one of the eight members of the Arabidopsis ferric reductase oxidase (FRO) family, FRO7, localizes to the chloroplast. Chloroplasts prepared from fro7 loss-of-function mutants have 75% less Fe(III) chelate reductase activity and contain 33% less iron per microgram of chlorophyll than wild-type chloroplasts. This decreased iron content is presumably responsible for the observed defects in photosynthetic electron transport. When germinated in alkaline soil, fro7 seedlings show severe chlorosis and die without setting seed unless watered with high levels of soluble iron. Overall, our results provide molecular evidence that FR07 plays a role in chloroplast iron acquisition and is required for efficient photosynthesis in young seedlings and for survival under iron-limiting conditions.