| Schlicht M, Strnad M, Scanlon MJ, Mancuso S, Hochholdinger F, Palme K, Volkmann D, Menzel D, Baluška F |
| Immunolocalization of auxin using a new specific antibody revealed, besides the expected diffuse cytoplasmic signal, the enrichment of auxin at the cross-walls (synapses), within endosomes, as well as within nuclei of those root apex cells which accumulate abundant F-actin. In Brefeldin A (BFA) treated roots, a strong auxin signal was scored within BFA compartments of F-actin-enriched cells having abundant auxin at synapses and within endosomes, but not in other root cells. Interestingly, several types of polar auxin transport (PAT) inhibitors exert the same inhibitory effects on endocytosis, vesicle recycling, and enrichment of F-actin at the synapses. These findings indicate that auxin is secreted across F-actin-enriched synapses via a vesicular neurotransmitter-like mode. This new concept finds genetic support via the semaphore1, rum1, and rum1/lrt1 mutants of maize which are impaired in PAT, endocytosis and vesicle recycling at synapses, as well as in recruitments of F-actin to the auxin transporting synapses. |
