Abstract
Manganese (Mn) and zinc (Zn) play essential roles in plants. Members of the natural resistance-associated macrophage protein (NRAMP) family transport divalent metal ions. In this research, the function of peanut (Arachis hypogaea L.) AhNRAMP1 in transporting Mn and Zn, as well as its potential for iron(Fe) and Zn biofortification was examined. AhNRAMP1 transcription was strongly induced by Mn- or Zn-deficiency in roots and stems of peanut. Yeast complementation assays suggested that AhNRAMP1 encoded a functional Mn and Zn transporter. Exogenous expression of AhNRAMP1 in tobacco and rice enhanced Mn or Zn concentrations, improving tolerance to Mn or Zn deficiency. With higher Mn concentration, transgenic plants exhibited inhibited growth under Mn excess condition; similar results were obtained under excessive Zn treatment. AhNRAMP1 expression increased biomass in transgenic tobacco and rice, as well as yield in transgenic rice grown on calcareous soil. Compared with non-transformed (NT) plants, Fe and Zn concentrations were elevated whereas concentrations of Mn, copper (Cu), and cadmium (Cd) were not enhanced. These results revealed that AhNRAMP1 contributes to Mn and Zn transport in plants and may be a candidate gene for Fe and Zn biofortification.
Highlights
Manganese and Zn are essential micronutrients for plant growth
AhNRAMP1 expression increased biomass in transgenic tobacco and rice, as well as yield in transgenic rice grown on calcareous soil
AhNRAMP1 transcript level in roots was significantly increased by threefold after treatment without Mn for 10 days compared with control (Figure 1)
Summary
Manganese and Zn are essential micronutrients for plant growth. Mn is required for photosynthesis and acts as a cofactor of numerous enzymes (Ishimaru et al, 2012a). Mn deficiency in plants causes interveinal chlorosis and impairs many physiological processes, leading to reduced biomass (Schmidt et al, 2016). Zn deficiency leads to leaf chlorosis, photosynthesis inhibition, biomass reduction, and generation of reactive. AhNRAMP1 in Manganese and Zinc Transport oxygen species (Sinclair and Krämer, 2012). Excessive Mn or Zn is harmful to plants. Excessive Mn results in oxidative stress and disturbs enzyme activity (Millaleo et al, 2010). Necrosis of old leaves and reduced biomass are triggered by excessive Zn (Tsonev and Lidon, 2012)
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