水稻OsNramp4介导锰离子吸收和转运的功能分析

Functional Analysis of OsNramp4 on Manganese Ion Uptake and Translocation in Rice

摘要

锰(Mn)是植物生长发育必需的矿质营养元素。水稻天然抗性相关巨噬细胞蛋白(natural resistance-associated macrophage protein, OsNramp)家族有7个成员, 其中4个具有Mn2+转运活性。OsNramp4已被鉴定为一个铝离子转运蛋白, 但尚未报道其是否具有Mn2+转运活性。本文利用Mn2+吸收突变株Δsmf1进行OsNramp4功能互补实验, 分析OsNramp4对Mn2+的响应, 研究环境Mn2+胁迫对敲除突变体nramp4的生长势以及Mn2+吸收和转运的影响。结果显示: OsNramp4能互补Δsmf1的Mn2+吸收缺陷表型; 水稻根部OsNramp4的表达受Mn2+的诱导; 高Mn2+胁迫下, nramp4的长势明显优于野生型对照, 突变体地上部Mn2+含量显著低于野生型, 且根-茎Mn2+转运率明显低于野生型, 暗示OsNramp4可能作为一个低亲和性Mn2+转运蛋白, 具有在高Mn2+环境下吸收Mn2+, 并由根部向地上组织运输Mn2+的功能。本研究结果对深入探讨植物Mn2+吸收、转运和分配的分子机制具有重要意义。

Abstract

Manganese (Mn) is an essential mineral nutrient element for plant growth and development. Seve-ral members of natural resistance-associated macrophage protein (OsNramp) family in rice have shown Mn2+ transport activity, among which OsNramp4 has been identified as an aluminum transporter, but it is still un-known whether OsNramp4 has Mn2+ transport activity. This paper utilized Mn2+ absorption mutant strain Δsmf1 to perform OsNramp4 functional complementation analysis, analyzed response of OsNramp4 to Mn2+, and studied the effects of environmental Mn2+ stress on the growth and Mn2+ uptake and transport of nramp4 knockout mutant. The results showed that OsNramp4 can complement Mn2+ uptake defect phenotype in Δsmf1 yeasts. The expression of OsNramp4 in root of rice was induced by Mn2+. The growth of nramp4 under high Mn2+ stress was significantly better than that of the wild-type control. Meanwhile, both the content of Mn2+ in the shoot of nramp4 mutant and the root-to-shoot translocation ration of Mn2+ were significantly lower than those of the wild type. These data suggested that OsNramp4 might function as a low-affinity Mn2+ transporter with activity of Mn2+ uptake under high Mn2+ stress and capacity of Mn2+ transport from root to aboveground tissue. These results are of great significance for further exploring the molecular mechanisms of Mn2+ uptake, transport and distribution in plants.

关键词

锰离子转运蛋白 / 水稻天然抗性相关巨噬细胞蛋白4 (OsNramp4) / 水稻

Key words

Mn2+ transporter / natural resistance-associated macrophage protein 4 (OsNramp4) / Oryza sativa L.