Putative RopGAPs impact division plane selection and interact with kinesin-12 POK1

Area of Science:

• Plant cell biology
• Molecular genetics
• Cytoskeletal regulation

Background:

• Cell morphology in plants relies on spatial control of cell division and expansion.
• Rho GTPase signaling regulates polarity and expansion in eukaryotes but its role in plant mitosis was unknown.

Purpose of the Study:

• To investigate the role of Rho GTPase signaling in plant mitotic events.
• To identify proteins interacting with POK1, a key component of the cortical division zone.

Main Methods:

• Yeast two-hybrid or co-immunoprecipitation to identify interacting proteins.
• Confocal microscopy to analyze protein localization during cell cycle.
• Analysis of Arabidopsis mutants (pok1, pok2, phgap1, phgap2) to assess cell wall positioning and division plane defects.

Main Results:

• Identified two Rho GTPase activating proteins (PHGAPs) that interact with the mitosis-specific kinesin-12 POK1.
• PHGAPs localize to the cortical division zone (CDZ/CDS) during mitosis in a POK-dependent manner.
• phgap1 phgap2 double mutants exhibit defects in cell wall positioning due to inaccurate POK1 localization.

Conclusions:

• Rho GTPase signaling, via PHGAPs, is implicated in plant mitotic events.
• PHGAPs play a role in division plane selection by influencing the positioning of the CDZ/CDS.
• Loss of PHGAP function disrupts the maintenance of plant cell morphology during proliferative divisions.