Transcription factor bHLH121 regulates root cortical aerenchyma formation in maize

Area of Science:

• Plant Biology
• Agronomy
• Genetics

Background:

• Root anatomical phenotypes, such as root cortical aerenchyma (RCA), are crucial for enhancing crop water and nutrient uptake, thereby improving yield and climate resilience.
• Studying RCA formation has been limited by the lack of high-throughput phenotyping platforms.

Purpose of the Study:

• To quantify variation in RCA formation across diverse maize lines using a novel phenotyping approach.
• To identify genetic factors controlling RCA formation and validate their function in crop improvement.

Main Methods:

• Utilized laser ablation tomography (Anatomics) for high-throughput RCA phenotyping in 436 maize lines.
• Conducted genome-wide association studies (GWAS) to identify candidate genes.
• Performed functional validation using transposon mutants, CRISPR/Cas9 gene editing, and overexpression lines for the identified gene, bHLH121.

Main Results:

• Significant and heritable variation in RCA formation was observed across the maize lines.
• GWAS identified a single-nucleotide polymorphism linked to bHLH121, a root cortex-expressed transcription factor gene.
• bHLH121 plays a critical role in RCA development and is essential for RCA formation under water and nitrogen stress.

Conclusions:

• The gene bHLH121 is a key regulator of root cortical aerenchyma formation in maize.
• bHLH121 is required for RCA development and stress adaptation, making it a valuable target for breeding crops with enhanced soil exploration and yield under suboptimal conditions.