Formation of self-organizing functionally distinct Rho of plants domains involves a reduced mobile population

Area of Science:

• Cell Biology
• Molecular Plant Biology

Background:

• Rho family proteins regulate eukaryotic cell polarity.
• Rho of Plants-Guanyl nucleotide Exchange Factor (ROPGEF) and ROP GTPase-Activating Protein (ROPGAP) are known to form self-organizing polar domains with Rho of Plants (ROP) proteins.
• Mechanisms of ROP domain formation and function remain unclear.

Purpose of the Study:

• To investigate the formation and localization of ROPs within self-organizing polar domains.
• To elucidate the molecular mechanisms underlying ROP domain formation and function.
• To explore the role of ROP domains in recruiting effector proteins.

Main Methods:

• Co-expression of ROPs, ROPGEF3, and GAP1 in Nicotiana benthamiana and Arabidopsis thaliana.
• Time-lapse imaging and Fluorescence Recovery After Photobleaching (FRAP) to analyze ROP mobility.
• Analysis of ROP interaction with anionic lipids and Rho GTP Dissociation Inhibitor (GDI) mediated recycling.
• Co-expression with ROP effector INTERACTOR OF CONSTITUTIVELY ACTIVE ROP 1 (ICR1).

Main Results:

• Six different ROPs formed self-organizing domains when co-expressed with ROPGEF3 and GAP1.
• Domain formation correlated with ROP-ROPGEF3 association and reduced ROP mobility.
• Domain formation was independent of Rho GDI mediated recycling.
• Activation/inactivation cycles and interaction with anionic lipids via a C-terminal polybasic domain were crucial for domain formation.
• ROP domains exhibited differential abilities to recruit the effector ICR1.

Conclusions:

• ROP proteins form self-organizing domains through specific interactions and regulated mobility.
• Activation cycles and lipid binding are key mechanisms for ROP domain formation.
• These ROP domains play a role in recruiting downstream effectors, influencing cellular processes.