Trafficking modulator TENin1 inhibits endocytosis, causes endomembrane protein accumulation at the pre-vacuolar compartment and impairs gravitropic response in Arabidopsis thaliana.
Biochem J. 2014; 460:177-185
Paudyal R, Jamaluddin A, Warren JP, Doyle SM, Robert S, Warriner SL, Baker A

Auxin gradients are established and maintained by polarised distribution of auxin transporters that undergo constitutive endocytic recycling from the plasma membrane (PM) and are essential for gravitropic response in plants. This study characterises an inhibitor of endomembrane protein trafficking, Trafficking & ENdocytosis inhibitor 1, TENin1 (TE1) that reduces gravitropic root bending in Arabidopsis thaliana seedlings. Short term TE1 treatment causes accumulation of plasma membrane (PM) proteins including brassinosteroid receptor BRI1, plasma membrane intrinsic protein 2a (PIP2a) and auxin transporter PIN-FORMED 2 (PIN2) in a pre-vacuolar related compartment (PVC), which is sensitive to Brefeldin A (BFA). This compound inhibits endocytosis from the PM, and promotes trafficking to the vacuole, consistent with inhibition of retrieval of proteins to the trans-Golgi network (TGN) from the PVC and the PM. However, trafficking of newly synthesised proteins to the PM is unaffected. The short term protein trafficking inhibition and long term effects on plant growth and survival, caused by TE1 were fully reversible upon drug washout. Structure activity relationship studies revealed that only minor modifications were possible without loss of biological activity. Diversity in Arabidopsis ecotypes was also exploited to identify two Arabidopsis accessions that display reduced sensitivity to TE1. This compound and the resistant Arabidopsis accessions may be used as a resource in future studies to better understand endomembrane trafficking in plants.
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