Variation in NRT1.1B contributes to nitrate-use divergence between rice subspecies

Area of Science:

• Plant molecular biology
• Agricultural science
• Genetics

Background:

• Asian cultivated rice (Oryza sativa L.) comprises indica and japonica subspecies.
• Indica rice exhibits higher nitrate absorption than japonica, but the underlying molecular basis is unknown.

Purpose of the Study:

• To investigate the molecular mechanisms behind the divergence in nitrate use between indica and japonica rice subspecies.
• To identify specific genes contributing to differential nitrate uptake and utilization.

Main Methods:

• Phylogenetic analysis of the nitrate-transporter gene NRT1.1B (OsNPF6.5).
• Association studies linking NRT1.1B variation to nitrate uptake, transport, and gene expression.
• Field trials using near-isogenic and transgenic lines to assess the impact of NRT1.1B alleles on yield and nitrogen-use efficiency (NUE).

Main Results:

• Phylogenetic analysis revealed divergence in NRT1.1B between indica and japonica subspecies.
• NRT1.1B variation in indica was associated with enhanced nitrate uptake, root-to-shoot transport, and upregulated nitrate-responsive genes.
• Japonica rice carrying the NRT1.1B-indica allele demonstrated significantly improved grain yield and NUE in field tests.

Conclusions:

• Variation in the NRT1.1B gene largely accounts for the divergence in nitrate use between indica and japonica rice.
• The NRT1.1B-indica allele holds potential for enhancing the NUE and grain yield of japonica rice varieties.