Essential developmental processes in Physcomitrium patens require distinct levels of total activity provided by...

Area of Science:

• Plant molecular biology
• Developmental biology
• Evolutionary biology

Background:

• RAS homologous (RHO) GTPases are vital regulators of cellular processes in eukaryotes.
• Plant-specific ROP GTPase families evolved and diversified with vascular plants.
• Nonvascular plants have fewer ROP members, making their functions less understood.

Purpose of the Study:

• To systematically investigate the essential functions of ROP GTPases (PpROPs) in the non-vascular moss Physcomitrium patens.
• To elucidate the roles of PpROPs in cell proliferation, differentiation, and gametophore formation.
• To understand the evolutionary context of ROP GTPase regulation in early land plants.

Main Methods:

• Generating knockout lines for individual and combined PpROP genes.
• Complementing knockout lines with wild-type or mutated PpROPs and heterologous homologs.
• Inducing PpROP gene overexpression.

Main Results:

• Discovered previously unknown PpROP functions in cell proliferation, caulonema differentiation, and gametophore development.
• Demonstrated variable dependence of PpROP functions on GDP/GTP cycling and distinct downstream signaling pathways.
• Showed that distinct developmental processes require specific total PpROP activity levels, not necessarily individual PpROPs.

Conclusions:

• PpROPs play essential, previously unrecognized roles in Physcomitrium patens development.
• PpROP signaling is complex, involving distinct downstream pathways and activity levels.
• These findings offer insights into the evolution of ROP/RHO GTPase regulation in early land plant development.