The 30th International Conference on Arabidopsis Research (ICAR 2019)

435 / 2019-01-29 10:44:07

The auxin transport inhibitor targets villin-generated actin bundles to regulate polar auxin transport in Arabidopsis

actin cytoskeleton, auxin trasport

Plenary track > Cell Biology

Actin cytoskeleton regulates auxin transport by controlling polar localization of auxin transporters such as PIN2. Inhibitors of polar auxin transport have been essential tools in understanding auxin-dependent plant development. One mode of their inhibitory effect is to affect actin dynamics, however, the underlying mechanisms remain unclear.Here, we demonstrate that auxin transport inhibitor such as TIBA target villin-mediated actin bundles to inhibit auxin transport. Multiple villin isovariants are targeted by TIBA, among which, villin4 (VLN4) has the highest affinity to this inhibitor. Mutants of VLN4 have significantly reduced TIBA sensitivity. Loss of VLN4 results in low abundance of actin bundles. Furthermore, VLN4-dependent actin bundling controls the PM presence of auxin exporter and subsequent auxin transport, which is critical for the inhibitory effect of TIBA. Biochemical approaches and docking simulation demonstrate that TIBA directly interacts with the C-terminal headpiece domain of villins. The VHP-TIBA interaction promotes villin to oligomerize, which facilitate cross-linking of actin filament. Villin VHP confers in-vivo TIBA sensitivity. VLN4 lacking VHP domain fails to mediate the action of TIBA on both actin cytoskeleton and auxin transport in plant. Thus, our study show that villins mediates the action of TIBA on actin dynamics; Villin-generated actin bundles determine downstream location of auxin efflux transporters and regulate polar auxin transport.