Regulation of ROP-mediated signal transduction during cell division and cell polarity establishment by a small RopGAP subfamily

01.07.2015 bis 31.08.2018

Polarity establishment regulates cell morphology and is an important
developmental process. The protagonists of cell polarity
establishment are Rho/Rac small GTPases that are activated by
guanine exchange factors (GEF), while interaction with GTPase
activating proteins (GAP) stimulate their sluggish GTPase activity and
renders them inactive. In plants, the activity of Rho of plants (ROP)
and its downstream effectors locally controls cell expansion via
orchestrated nucleation and organization of the cytoskeleton at the
plasma membrane. We identified members of a small family of
RhoGAPs, PHGAP1 and PHGAP2 as interaction partners of kinesin-
12 motor proteins (POKs). POKs are required for the maintenance of
the division plane throughout mitosis, distinctly localizing to the
cortical division site. The pleiotropic phenotype of phgap1 phgap2
double mutants indicates that PHGAPs act in cell division and in cell
expansion. In the proposed work we will determine the role of
PHGAPs in division plane maintenance and how regulation of ROP
activity contributes to the organization of specific cytoskeletal
formations during cell division. Furthermore, to gain insight on
PHGAP function on the molecular level, we will perform protein
domain and promoter swap experiments to determine how specificity
for interaction with different ROPs is mediated. The proposed
research will combine molecular-genetic, cell biological and
biochemical approaches to achieve these goals.