Cell-type specification at criticality underlies rhizoid patterning in the liverwort Marchantia polymorpha

Area of Science:

• Plant development
• Developmental biology
• Cellular differentiation

Background:

• Rhizoid specification in Marchantia polymorpha involves lateral inhibition mediated by microRNA FRH1, repressing the transcription factor RSL1.
• Patterning of rhizoid precursor cells, appearing isolated or in small clusters, is not fully understood at the molecular level.

Purpose of the Study:

• To elucidate the molecular mechanisms driving rhizoid patterning in Marchantia polymorpha.
• To investigate the role of local activation and lateral inhibition in RSL1 expression and FRH1 diffusion.

Main Methods:

• Mathematical modeling to simulate rhizoid patterning.
• Analysis of FRH1 diffusion and its effect on RSL1 activation.
• Comparison of model predictions with wild-type and mutant experimental data.

Main Results:

• Rhizoid patterning is consistent with local RSL1 activation modulated by FRH1-mediated lateral inhibition via diffusion.
• FRH1 mobility acts as a diffusion-driven switch, creating sharp transitions between uniform and patterned states.
• The model successfully reproduces spatial statistics of wild-type and mutant phenotypes.

Conclusions:

• Rhizoid precursor cell initiation is stochastic and refined by lateral inhibition.
• A diffusion-driven switch mechanism, involving FRH1 mobility, underlies rhizoid patterning.
• This study highlights a key patterning mechanism in cellular differentiation and tissue morphogenesis.