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bioRxiv · 10.1101/2023.12.06.570355

Rapid Vacuolar Sorting of the Borate Transporter BOR1 Requires the Adaptor Protein Complex AP-4 in Arabidopsis

Yoshinari, A.·Shimizu, Y.·Hosokawa, T.·Nakano, A.·Uemura, T.·Takano, J.
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Abstract

Plants maintain nutrient homeostasis by controlling the activities and abundance of nutrient transporters. In Arabidopsis thaliana, the borate (B) transporter BOR1 plays a role in the efficient translocation of B under low-B conditions. BOR1 undergoes polyubiquitination in the presence of sufficient B and is then transported to the vacuole via multivesicular bodies (MVBs) to prevent B accumulation in tissues at a toxic level. A previous study indicated that BOR1 physically interacts with subunits of adaptor protein complexes AP-3 and AP-4, both involved in vacuolar sorting pathways. In this study, we investigated the roles of AP-3 and AP-4 subunits in BOR1 trafficking in Arabidopsis. The lack of AP-3 subunits did not affect either vacuolar sorting or polar localization of BOR1-GFP, whereas the absence of AP-4 subunits resulted in a delay in high-B-induced vacuolar sorting without affecting polar localization. Super-resolution microscopy revealed a rapid sorting of BOR1-GFP into AP-4-positive spots in the trans-Golgi network (TGN) upon high-B supply. These results indicate that AP-4 is involved in sequestration of ubiquitinated BOR1 into a TGN-specific subdomain "vacuolar-trafficking zone," and is required for efficient sorting to MVB and vacuole. Our findings elucidate the rapid vacuolar sorting process facilitated by AP-4 in plant nutrient transporters. Subject areas(7) Membrane and transport

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Yoshinari, A., Shimizu, Y., Hosokawa, T., Nakano, A., Uemura, T., Takano, J.. 2023-12-06. Rapid Vacuolar Sorting of the Borate Transporter BOR1 Requires the Adaptor Protein Complex AP-4 in Arabidopsis. https://doi.org/10.1101/2023.12.06.570355

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