Opposite polarity programs regulate asymmetric subsidiary cell divisions in grasses

Area of Science:

• Plant Biology
• Developmental Biology
• Cell Biology

Background:

• Grass stomata rely on lateral subsidiary cells (SCs) for their unique morphology and efficient gas exchange.
• Subsidiary mother cells (SMCs) must polarize before an asymmetric division to form SCs.
• The proximal polarity module (e.g., PANGLOSS1) is known, but other developmental factors for SC formation are unclear.

Purpose of the Study:

• To identify novel factors involved in subsidiary cell (SC) formation in grasses.
• To elucidate the molecular mechanisms coordinating SC development and division.

Main Methods:

• Comparative transcriptomics of wild-type and SC-less bdmute mutant leaves in Brachypodium distachyon.
• Analysis of polarity domain formation and function in subsidiary mother cells.

Main Results:

• Discovery of BdPOLAR, forming a novel distal polarity domain in SMCs, opposing the proximal PAN1 domain.
• Both proximal and distal polarity domains are essential for SC division.
• The proximal domain regulates the distal domain's polarization, coordinating nuclear migration and division plane orientation.

Conclusions:

• Two opposing polarity domains in SMCs coordinate the asymmetric division forming SCs.
• This coordinated process is critical for grass stomatal development and physiology.
• BdPOLAR plays a key role in establishing distal polarity during SC formation.