Overexpressing of OsAMT1-3, a High Affinity Ammonium Transporter Gene, Modifies Rice Growth and Carbon-Nitrogen Metabolic Status.

Aili Bao,Hongmei Cai,Zhuqing Zhao,Zhijun Liang

doi:10.3390/ijms16059037

Abstract

AMT1-3 encodes the high affinity NH4+ transporter in rice roots and is predominantly expressed under nitrogen starvation. In order to evaluate the effect of AMT1-3 gene on rice growth, nitrogen absorption and metabolism, we generated AMT1-3-overexpressing plants and analyzed the growth phenotype, yield, carbon and nitrogen metabolic status, and gene expression profiles. Although AMT1-3 mRNA accumulated in transgenic plants, these plants displayed significant decreases in growth when compared to the wild-type plants. The nitrogen uptake assay using a 15N tracer revealed poor nitrogen uptake ability in AMT1-3-overexpressing plants. We found significant decreases in AMT1-3-overexpressing plant leaf carbon and nitrogen content accompanied with a higher leaf C/N ratio. Significant changes in soluble proteins and carbohydrates were also observed in AMT1-3-overexpressing plants. In addition, metabolite profile analysis demonstrated significant changes in individual sugars, organic acids and free amino acids. Gene expression analysis revealed distinct expression patterns of genes that participate in carbon and nitrogen metabolism. Additionally, the correlation between the metabolites and gene expression patterns was consistent in AMT1-3-overexpressing plants under both low and high nitrogen growth conditions. Therefore, we hypothesized that the carbon and nitrogen metabolic imbalance caused by AMT1-3 overexpressing attributed to the poor growth and yield of transgenic plants.

Highlights

Nitrogen (N) is one of the essential macronutrients required for plant growth and development and is often a major limiting factor for plant productivity and crop yield [1,2]
The OsAMT1-3 gene was amplified from the rice (Zhonghua 11, Japonica) genome and ligated into the pCAMBIA 1301S vector, which contained a hygromycin resistance gene driven by the CaMV35S promoter
Southern blot analysis showed 1–2 copies of transgene existed in the OsAMT1-3-overexpressing plants (Figure S1)

Summary

Introduction

Nitrogen (N) is one of the essential macronutrients required for plant growth and development and is often a major limiting factor for plant productivity and crop yield [1,2]. Higher plants can absorb and use various forms of nitrogen components from the soil, most notably the inorganic ions ammonium (NH4+) and nitrate (NO3−). These ions are believed to be the principal nitrogen sources for plant growth in agricultural and most natural environments, as it is required in greater amounts than any other mineral nutrient [5]. The optimal functioning of the metabolic pathways for carbon and nitrogen assimilation in plants, and maintaining an appropriate balance or ratio of carbohydrates to nitrogen metabolites in the cell, which is referred to as the “carbon/nitrogen balance”, are critical for determining plant growth, biomass accumulation and seed production [8,9,10,11,12]

Methods

Results

Discussion

Conclusion