Project Details
Projekt
RhoGTPase signalling in double fertilisation in Arabidopsis and maize (A15)
Subject Area
Plant Cell and Developmental Biology
Term
from 2021 to 2023
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 170483403
Double fertilisation is a key process for seed production in all flowering plants and therefore crucial for crop production. During double fertilisation, two male sperm cells fuse with two female gametes, which develop into the embryo and the nurturing endosperm, respectively. An essential feature of this process is that the tip of the pollen tube grows directionally through the floral tissue and delivers male gametes to the female gametophyte (Bleckmann et al., 2014; Dresselhaus et al., 2016). This polar tip growth requires multiple feedback loops for balanced cellular expansion and stability. The RhoGTPases RHO OF PLANTS (ROPs) are central factors to integrate these feedback loops. Their activity is regulated by activating ROP guanine nucleotide exchange factors (ROPGEFs) and inactivating GTPase-Activating Proteins (GAPs) (Qin and Yang, 2011). In previous studies, only individual proteins or mechanisms were investigated. We and others, however, showed that multiple of these factors, although expressed in the same cell, act in concert or in sequence. Additionally, we found that distinct ROPGEFs regulate either localisation or activity of the same ROP in root hairs, a second polar tip growth process in plants (Denninger et al., 2019). Based on these observations of distinct ROPGEF functions in root hairs, I hypothesise that different aspects of ROP signalling are regulated by different ROPGEFs in pollen tubes. A better understanding of ROPGEFs during pollen tube growth would enhance our understanding of seed production.In this project, we will investigate the specific functions of three, preferentially pollen-expressed ROPGEFs in pollen tubes during tip growth and gamete interaction in Arabidopsis thaliana. We aim to identify their specific functions on ROP localisation and activation by examining Ca2+ signalling and actin organisation as readouts. To study the conservation of these mechanisms between plants, we will investigate ROPGEF function in pollen tubes of Zea mays using knock-out and knock-down mutants and compare this to ROPGEF function in Arabidopsis. Additionally, we will investigate ROP signalling in the female Arabidopsis gametophyte, where this pathway remains completely unexplored. Preliminary results support expression of at least one ROPGEF in this tissue, and we will further investigate the presence of other ROP signalling factors, as well as their function in cells of the female gametophyte during double fertilisation.
DFG Programme
Collaborative Research Centres
Applicant Institution
Technische Universität München (TUM)
Project Head
Dr. Philipp Denninger
