Enhancing maize's nitrogen-fixing potential through ZmSBT3, a gene suppressing mucilage secretion

Area of Science:

• Plant biology
• Genetics
• Agricultural science

Background:

• Maize (Zea mays) cultivation is limited by high nitrogen requirements.
• Ancient maize landraces utilized diazotrophic bacteria in aerial root mucilage (ARM) for nitrogen fixation.
• The retention of this nitrogen-fixing trait in modern maize is largely unknown.

Purpose of the Study:

• To investigate the prevalence and characteristics of ARM in modern maize inbred lines.
• To identify genetic factors associated with ARM secretion and nitrogen-fixing potential.
• To assess the role of ZmSBT3 in regulating ARM and its impact on plant growth.

Main Methods:

• Field study of ARM secretion in 258 modern maize inbred lines.
• Genome-wide association study (GWAS) to identify candidate genes for ARM.
• Gene knockout experiments targeting ZmSBT3 to evaluate its function.
• Analysis of nitrogen-fixing enzyme activity and bacterial populations in ARM.

Main Results:

• ARM secretion is common in modern maize, with significant variation in amount.
• Only a few modern lines retained high nitrogen-fixing traits from ancient landraces.
• The subtilase gene ZmSBT3 was identified as a negative regulator of ARM secretion.
• ZmSBT3 knockout lines showed increased biomass and nitrogen accumulation under nitrogen-limited conditions.
• High ARM was linked to specific ZmSBT3 haplotypes lost during domestication.

Conclusions:

• ZmSBT3 is a key regulator of ARM secretion in maize.
• Targeting ZmSBT3 offers a strategy to enhance ARM and nitrogen fixation in maize.
• This research provides a potential avenue for developing more nitrogen-efficient maize varieties.