This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Cells rely on complex signaling networks in which different molecular pathways communicate with one another. Small GTPases act as molecular switches in these networks, controlling diverse cellular processes such as intracellular transport and cell morphogenesis.
Although crosstalk between different families of small GTPases is established in animal cells, whether and how such crosstalk occurs in plants has remained largely unknown. A research team led by Associate Professor Emi Ito and Professor Takashi Ueda at the National Institute for Basic Biology (NIBB), together with collaborators at Ochanomizu University, Kyoto Prefectural University, Saitama University, Nagoya University and RIKEN, has uncovered a molecular mechanism that connects two distinct types of small GTPases in the model plant Arabidopsis thaliana. The study is published in Nature Plants.
The researchers identified a protein called REAP1/SWAP70 that links RAB5, a small GTPase involved in intracellular membrane trafficking, with ROP7, a member of the plant-specific ROP (Rho of Plants) family of small GTPases involved in processes such as cell morphogenesis. Their findings reveal a previously unknown RAB5-REAP1-ROP7 signaling pathway and show that this pathway plays an important role in normal pollen development. Plants have evolved their own repertoire of small GTPases.
These include ARA6, a plant-unique member of the RAB5 family, as well as ROPs, a plant-specific group within the Rho family of small GTPases. While these proteins regulate a variety of plant-specific cellular processes, it has remained unclear whether different small GTPase families communicate with one another. Using Arabidopsis, the researchers found that REAP1 interacts with both the plant-unique RAB5 member ARA6 and canonical RAB5 proteins that are widely conserved in eukaryotic cells.
REAP1 localizes to endosomes, intracellular compartments that serve as hubs for membrane trafficking. This localization depends on interactions with both RAB5 and specific membrane lipids. The team further discovered that REAP1 binds to ROP7.
Overexpression of RAB5 promoted the recruitment of ROP7 to endosomes, whereas this recruitment did not occur in cells lacking REAP1. These findings indicate that REAP1 acts as a molecular bridge connecting RAB5 and ROP7. Importantly, disrupting this signaling network affected pollen development.
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