Yokosho Kengo, Yamaji Naoki, Ma Jian Feng
Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, 710-0046 Japan.
Plant Cell Physiol. 2021 Sep 24;62(4):600-609. doi: 10.1093/pcp/pcaa153.
Manganese (Mn) is an essential element for plant growth and development, but transporters required for Mn uptake have only been identified in a few plant species. Here, we functionally characterized a member of the natural resistance-associated macrophage proteins (Nramps) family, FeNramp5 in buckwheat (Fagopyrum esculentum Moench), which is known as a species well adapted to acidic soils. FeNramp5 was mainly expressed in the roots, and its expression was upregulated by the deficiency of Mn and Fe. Furthermore, spatial and tissue-specific expression analysis showed that FeNramp5 was expressed in all tissues of the basal root regions. FeNramp5-GFP protein was localized to the plasma membrane when transiently expressed in buckwheat leaf protoplast. FeNramp5 showed the transport activity for Mn2+ and Cd2+ but not for Fe2+ when expressed in yeast. Furthermore, the transport activity for Mn2+ was higher in yeast expressing FeNramp5 than in yeast expressing AtNramp1. FeNramp5 was also able to complement the phenotype of Arabidopsis atnramp1 mutant in terms of the growth and accumulation of Mn and Cd. The absolute expression level of AtNramp1 was comparable to that of FeNramp5 in the roots, but buckwheat accumulated higher Mn than Arabidopsis when grown under the same condition. Further analysis showed that at least motif B in FeNramp5 seems important for its high transport activity for Mn. These results indicate that FeNramp5 is a transporter for the uptake of Mn and Cd and its higher transport activity for Mn is probably associated with higher Mn accumulation in buckwheat.
锰（Mn）是植物生长发育所必需的元素，但仅在少数植物物种中鉴定出了锰吸收所需的转运蛋白。在此，我们对自然抗性相关巨噬细胞蛋白（Nramps）家族的一个成员——荞麦（苦荞麦）中的FeNramp5进行了功能表征，荞麦是一种已知非常适应酸性土壤的物种。FeNramp5主要在根中表达，其表达受锰和铁缺乏的上调。此外，空间和组织特异性表达分析表明，FeNramp5在基部根区域的所有组织中均有表达。当在荞麦叶原生质体中瞬时表达时，FeNramp5 - GFP蛋白定位于质膜。当在酵母中表达时，FeNramp5对Mn2 +和Cd2 +表现出转运活性，但对Fe2 +没有转运活性。此外，在表达FeNramp5的酵母中，Mn2 +的转运活性高于表达AtNramp1的酵母。在锰和镉的生长和积累方面，FeNramp5也能够互补拟南芥atnramp1突变体的表型。在根中，AtNramp1的绝对表达水平与FeNramp5相当，但在相同条件下生长时，荞麦积累的锰比拟南芥高。进一步分析表明，FeNramp5中至少基序B对其高锰转运活性似乎很重要。这些结果表明，FeNramp5是一种锰和镉吸收的转运蛋白，其对锰的较高转运活性可能与荞麦中较高的锰积累有关。
