Decoding nitrogen uptake efficiency in maize and sorghum: insights from comparative gene regulatory networks

Area of Science:

• Plant molecular biology
• Agricultural science
• Genomics

Background:

• Nitrogen (N) is crucial for plant growth, but optimizing nitrogen use efficiency (NUE) is a persistent agricultural challenge.
• Understanding the genetic regulation of plant responses to nitrogen availability is key to improving crop yields.

Purpose of the Study:

• To construct and analyze maize and sorghum nitrogen use efficiency gene regulatory networks (NUE GRNs).
• To identify conserved and species-specific regulatory mechanisms underlying early nitrogen responsiveness in plants.

Main Methods:

• Construction of a maize NUE GRN (mNUEGRN) using enhanced yeast one-hybrid assays, identifying 1625 protein-DNA interactions.
• Projection of a sorghum NUE GRN (spNUEGRN) and analysis of N-responsive subnetworks via transcriptome profiling under nitrogen stress.
• Cross-species comparison with an Arabidopsis GRN and Gini correlation analysis to identify conserved interactions and feed-forward loops (FFLs).

Main Results:

• Identified 1625 protein-DNA interactions in the mNUEGRN, with bZIP18 and bZIP30 as central regulators.
• Discovered approximately 18% conserved interactions between maize and Arabidopsis GRNs, particularly in nitrate assimilation.
• Uncovered 764 FFLs in mNUEGRN and 638 in spNUEGRN, with some identified in both leaf and root tissues, suggesting roles in modulating N-responsive transcription.

Conclusions:

• The study reveals conserved and species-specific regulatory strategies for early nitrogen responsiveness in maize and sorghum.
• Identified potential candidate regulatory motifs (FFLs) that warrant further investigation for their role in NUE.
• Provides a foundation for engineering crops with enhanced nitrogen use efficiency.