Gollhofer Julia, Timofeev Roman, Lan Ping, Schmidt Wolfgang, Buckhout Thomas J
Institute of Biology, Humboldt University Berlin, Berlin, Germany.
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy Sciences, Nanjing, PR China.
PLoS One. 2014 Oct 31;9(10):e110468. doi: 10.1371/journal.pone.0110468. eCollection 2014.
Iron deficiency is a nutritional problem in plants and reduces crop productivity, quality and yield. With the goal of improving the iron (Fe) storage properties of plants, we have investigated the function of three Arabidopsis proteins with homology to Vacuolar Iron Transporter1 (AtVIT1). Heterologous expression of Vacuolar Iron Transporter-Like1 (AtVTL1; At1g21140), AtVTL2 (At1g76800) or AtVTL5 (At3g25190) in the yeast vacuolar Fe transport mutant, Δccc1, restored growth in the presence of 4 mM Fe. Isolated vacuoles from yeast expressing either of the VTL genes in the Δccc1 background had a three- to four-fold increase in Fe concentration compared to vacuoles isolated from the untransformed mutant. Transiently expressed GFP-tagged AtVTL1 was localized exclusively and AtVTL2 was localized primarily to the vacuolar membrane of onion epidermis cells. Seedling root growth of the Arabidopsis nramp3/nramp4 and vit1-1 mutants was decreased compared to the wild type when seedlings were grown under Fe deficiency. When expressed under the 35S promoter in the nramp3/nramp4 or vit1-1 backgrounds, AtVTL1, AtVTL2 or AtVTL5 restored root growth in both mutants. The seed Fe concentration in the nramp3/nramp4 mutant overexpressing AtVTL1, AtVTL2 or AtVTL5 was between 50 and 60% higher than in non-transformed double mutants or wild-type plants. We conclude that the VTL proteins catalyze Fe transport into vacuoles and thus contribute to the regulation of Fe homeostasis in planta.
缺铁是植物中的一个营养问题，会降低作物的生产力、品质和产量。为了改善植物的铁（Fe）储存特性，我们研究了三种与液泡铁转运蛋白1（AtVIT1）具有同源性的拟南芥蛋白的功能。液泡铁转运蛋白样1（AtVTL1；At1g21140）、AtVTL2（At1g76800）或AtVTL5（At3g25190）在酵母液泡铁转运突变体Δccc1中的异源表达，在4 mM铁存在的情况下恢复了生长。与从未转化突变体中分离的液泡相比，在Δccc1背景中表达任一VTL基因的酵母中分离的液泡铁浓度增加了三到四倍。瞬时表达的绿色荧光蛋白标记的AtVTL1仅定位于洋葱表皮细胞的液泡膜，而AtVTL2主要定位于该膜。当幼苗在缺铁条件下生长时，拟南芥nramp3/nramp4和vit1-1突变体的幼苗根生长比野生型降低。当在nramp3/nramp4或vit1-1背景下的35S启动子下表达时，AtVTL1、AtVTL2或AtVTL5恢复了两个突变体中的根生长。过表达AtVTL1、AtVTL2或AtVTL5的nramp3/nramp4突变体种子铁浓度比未转化的双突变体或野生型植物高50%至60%。我们得出结论，VTL蛋白催化铁转运到液泡中，从而有助于调节植物体内铁的稳态。
