Gene expression biomarkers provide sensitive indicators of in planta nitrogen status in maize

Abstract

Over the last several decades, increased agricultural production has been driven by improved agronomic practices and añdramatic increase in the use of nitrogen-containing fertilizers to maximize the yield potential of crops. To reduce input costsñand to minimize the potential environmental impacts of nitrogen fertilizer that has been used to optimize yield, an increasedñunderstanding of the molecular responses to nitrogen under field conditions is critical for our ability to further improveñagricultural sustainability. Using maize (Zea mays) as a model, we have characterized the transcriptional response of plantsñgrown under limiting and sufficient nitrogen conditions and during the recovery of nitrogen-starved plants. We show that añlarge percentage (approximately 7%) of the maize transcriptome is nitrogen responsive, similar to previous observations inñother plant species. Furthermore, we have used statistical approaches to identify a small set of genes whose expression profilesñcan quantitatively assess the response of plants to varying nitrogen conditions. Using a composite gene expression scoringñsystem, this single set of biomarker genes can accurately assess nitrogen responses independently of genotype, developmentalñstage, tissue type, or environment, including in plants grown under controlled environments or in the field. Importantly, theñbiomarker composite expression response is much more rapid and quantitative than phenotypic observations. Consequently,ñwe have successfully used these biomarkers to monitor nitrogen status in real-time assays of field-grown maize plants underñtypical production conditions. Our results suggest that biomarkers have the potential to be used as agronomic tools to monitorñand optimize nitrogen fertilizer usage to help achieve maximal crop yields. © 2011 American Society of Plant Biologists. All Rights Reserved.