Expression of genes related to nitrogen metabolism in maize grown under organic and inorganic nitrogen supplies

Abstract

Application of organic nitrogen (N) has been proposed as a method to reduce potential environmental pollution due to N loss without sacrificing grain yield. The mechanism responsible for organic N regulation of maize (Zea mays L.) N metabolism is nonetheless largely unknown. In this study, we compared the expression of genes related to N assimilation and remobilization during the grain filling stage in maize plants grown under field conditions. We applied five different N treatments, which consisted of N supplied in organic and/or inorganic forms at the following rates: 0/45, 0/120, 0/240, 120/120, and 240/0 kg ha⁻¹ organic/inorganic N. Yield was found to increase with increasing N input, but no significant difference was found in grain yield among 0/240, 240/0 and 120/120 treatments. Organic N application tended to decrease N accumulation and to increase N utilization efficiency. Genes related to N assimilation activity in leaves, such as ZmNR1 and ZmFd-GOGAT1, were unaffected by different N forms. In contrast, genes related to N remobilization activity in leaves, such as ZmGS1.1 and ZmGDH1, were up-regulated, especially in old leaves, by the pure organic N supply treatment (240/0). These data suggest that application of pure organic N likely induces a N-deficiency response in maize plants, with a consequent increase in physiological N utilization efficiency due to up-regulation of key genes involved in N remobilization processes.

Key words:

• maize
• inorganic and organic nitrogen
• N assimilation and remobilization
• N utilization efficiency
• gene expression

ACKNOWLEDGMENTS

The authors gratefully acknowledge funding support from the European Seventh Framework Programme of the European Community for Research, Technological Development and Demonstration Activities for the Integrated Project NUE-CROPS FP7-CP-IP 222645. The views expressed in this publication are the sole responsibility of the authors, and do not necessarily reflect the views of the European Commission. Neither the European Commission nor any person acting on behalf of the Commission is responsible for any use that might be made of the information contained herein. This work was also supported by the National Basic Research Program (973 Program) of China (No. 2011CB100305) and the National Science Foundation of China (No. 31272233).