Abstract
Movement of nitrogen to the plant tissues where it is needed for growth is an important contribution to nitrogen use efficiency. However, we have very limited knowledge about the mechanisms of nitrogen transport. Loading of nitrogen into the xylem and/or phloem by transporter proteins is likely important, but there are several families of genes that encode transporters of nitrogenous molecules (collectively referred to as N transporters here), each comprised of many gene members. In this study, we leveraged publicly available microarray data of Arabidopsis to investigate the gene networks of N transporters to elucidate their possible biological roles. First, we showed that tissue-specificity of nitrogen (N) transporters was well reflected among the public microarray data. Then, we built coexpression networks of N transporters, which showed relationships between N transporters and particular aspects of plant metabolism, such as phenylpropanoid biosynthesis and carbohydrate metabolism. Furthermore, genes associated with several biological pathways were found to be tightly coexpressed with N transporters in different tissues. Our coexpression networks provide information at the systems-level that will serve as a resource for future investigation of nitrogen transport systems in plants, including candidate gene clusters that may work together in related biological roles.
Highlights
Nitrogen (N) is often the most limiting nutrient for plant growth
Arabidopsis expression series datasets we collected from GEO, 50 datasets are root-specific and 49 datasets are leaf-specific
Our results show that NPF2.13 was differentially expressed in only about 20% of roots but in about 40% of leaves (Figure 1)
Summary
Nitrogen (N) is often the most limiting nutrient for plant growth. Understanding the mechanisms of nitrogen utilization in plants will provide guidance to improve nitrogen use efficiency of crop plants, which will reduce fertilizer and energy costs of agriculture, and help protect our environment (Canfield et al, 2010). N is usually taken up by roots from the soil as nitrate or ammonium, or sometimes organic forms, such as amino acids (Masclaux-Daubresse et al, 2010). Nitrate and ammonium may be assimilated into organic forms in the roots or leaves through the glutamine synthetase-GOGAT (GS-GOGAT) cycle, and may be utilized or stored where synthesized, or translocated to other tissues (Masclaux-Daubresse et al, 2010). Some of the genes that control N transport have been identified, but other components remain to be identified and our understanding of the system is incomplete
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