Incredibly versatile plant hormone auxin suppresses clathrin-dependent endocytosis

1 October 2010
Clathrin-mediated endocytosis is an evolutionary highly conserved process that allows cells to take up molecules by the inward budding of plasma membrane vesicles. The system is best characterized in nerve terminals, where it plays a central role in the recycling of neurotransmitters. Now, Jiří Friml and his colleagues from the VIB Department of Systems Biology, UGent, have published an article in Cell, demonstrating that clathrin-mediated endocytosis in the model plant Arabidopsis is regulated by the plant hormone auxin.

What did you discover?

Jiří: We demonstrated that auxin signaling by the auxin-binding protein 1 (ABP1) receptor inhibits the clathrin-mediated internalization of PIN proteins. ABP1 acts as a positive factor in clathrin recruitment to the plasma membrane, thereby promoting endocytosis. Auxin binding to ABP1 interferes with this action and leads to the inhibition of clathrin-mediated endocytosis. The study demonstrates that ABP1 mediates a non-transcriptional auxin signaling that regulates clathrin-mediated endocytosis. This was inferred by the fact that the response time was well below that of transcriptional regulation. Furthermore, the study suggests that this signaling may be essential for the feedback of auxin on its own transport.

This system is highly important in plant development. Why?

Spatial distribution of auxin regulates multiple aspects of plant development. These self-regulating auxin gradients are established by the action of PIN auxin transporters, whose activity is regulated by their constitutive cycling between the plasma membrane and endosomes. In this cycling, PINs mediate auxin efflux from cells. Other studies have revealed that the different PIN proteins play a role in multiple developmental processes, including reactions of plants to gravity and light.

In the same issue of Cell you revealed another function of auxin, which one?

We described the role of this highly versatile plant hormone in the formation of the lobes and indentations of Arabidopsis leaf epidermal pavement cells (PCs).

ABP1 Mediates Auxin Inhibition of Clathrin-Dependent Endocytosis in Arabidopsis, Robert S et al., Cell. 2010 Oct 1;143(1):111-21

Cell Surface- and Rho GTPase-Based Auxin Signaling Controls Cellular Interdigitation in Arabidopsis, Xu T et al., Cell. 2010 Oct 1;143(1):99-110

Jiří Friml © 2007 Bert Stephani
download hi-res jpg