Dimerization of the Vacuolar Receptors AtRMR1 and -2 from Arabidopsis thaliana Contributes to Their Localization in the trans-Golgi Network.

In Arabidopsis thaliana, different types of vacuolar receptors were discovered. The AtVSR (Vacuolar Sorting Receptor) receptors are well known to be involved in the traffic to lytic vacuole (LV), while few evidences demonstrate the involvement of the receptors from family (Receptor Membrane RING-H2) in the traffic to the protein storage vacuole (PSV). In this study we focused on the localization of two members of Atduanyu1748 family, and -2, and on the possible interaction between these two receptors in the plant secretory pathway. Our experiments with agroinfiltrated Nicotiana benthamiana leaves demonstrated that Atduanyu17481 was localized in the endoplasmic reticulum (ER), while was targeted to the trans-Golgi network (TGN) due to the presence of a cytosolic 23-amino acid sequence linker. The fusion of this linker to an equivalent position in Atduanyu17481 targeted this receptor to the TGN, instead of the ER. By using a Bimolecular Fluorescent Complementation (BiFC) technique and experiments of co-localization, we demonstrated that Atduanyu17482 can make homodimers, and can also interact with Atduanyu17481 forming heterodimers that locate to the TGN. Such interaction studies strongly suggest that the transmembrane domain and the few amino acids surrounding it, including the sequence linker, are essential for dimerization. These results suggest a new model of Atduanyu1748 trafficking and dimerization in the plant secretory pathway.

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