Ground tissue circuitry regulates organ complexity in maize and Setaria

Area of Science:

• Plant biology
• Developmental biology
• Genetics

Background:

• Plant roots possess multiple cortex layers vital for physiological functions like flood tolerance and symbiosis.
• The formation of these cortical layers is poorly understood, especially in species with complex root anatomy beyond Arabidopsis.

Purpose of the Study:

• To investigate the molecular mechanisms underlying cortical layer formation in maize roots.
• To characterize the role of the SHORT-ROOT (SHR) pathway in maize root development.

Main Methods:

• Single-cell RNA sequencing to create a high-resolution cell map of the maize root.
• Analysis of SHR protein mobility within root tissues.
• Phenotypic analysis of higher-order SHR mutants in maize and Setaria.

Main Results:

• A novel configuration of the SHR transcription factor was identified adjacent to an expanded cortex in maize.
• Maize SHR protein exhibits hypermobility, migrating at least eight cell layers into the cortex.
• SHR pathway disruption in maize and Setaria mutants leads to a reduced number of cortical layers.

Conclusions:

• The SHR pathway is a key regulator controlling the expansion of cortical tissue in plant roots.
• SHR's hypermobility is essential for elaborating anatomical complexity in maize root cortex formation.
• This study reveals conserved mechanisms of root cortex development across different plant species.