Variation in Membrane Trafficking Linked to SNARE AtSYP51 Interaction With Aquaporin NIP1;1

Abstract

SYP51 and 52 are the two members of the SYP5 Qc-SNARE gene family in Arabidopsis thaliana. These two proteins, besides their high level of sequence identity (85%), have shown to have differential functional specificity and possess a different interactome. Here we describe a unique and specific interaction of SYP51 with an ER aquaporin, AtNIP1;1 (also known as NLM1) indicated to be able to transport arsenite [As(III)] and previously localized on PM. In the present work we investigate in detail such localization in vivo and characterize the interaction with SYP51. We suggest that this interaction may reveal a new mechanism regulating tonoplast invagination and recycling. We propose this interaction to be part of a regulatory mechanism associated with direct membrane transport from ER to tonoplast and Golgi mediated vesicle trafficking. We also demonstrate that NIP1;1 is important for plant tolerance to arsenite but does not alter its uptake or translocation. To explain such phenomenon the hypothesis that SYP51/NIP1;1 interaction modifies ER and vacuole ability to accumulate arsenite is discussed.

Endomembrane Reorganization Induced by Heavy Metals

“…If nip1;1ko has no effect on As(III) uptake it must control compartmentalization of the metalloid. Indeed this mutant or transgenic lines expressing tagged variants of NIP1;1 showed altered profiles for other elements uptake such as a reduction for Cu(II) and an increase for Zn(II) [48], confirming a role in metals and metalloids homeostasis. NIP1;1 was shown to interact with the vacuolar SNARE SYP51 and it is possible that through this interaction it regulates the vacuolar detoxification capacity.…”

“…Heavy metals cross membranes not only by transporters but also through the water channel called aquaporin (AQPs). AQPs belong to the family of Major Intrinsic Proteins (MIPs) [44] that transport other molecules of great physiological interest in addition to water [45] and are possibly engaged in structural roles [46][47][48]. In plants, MIPs form a large superfamily of proteins with more than thirty identified members in A. thaliana [49] and Populus trichocarpa [50].…”

“…AtNIP1;1 is an aquaglyceroporin able to transport arsenite (As[III]) and antimony, recently localized in vivo on ER membrane [48]. Its knock-out mutant (nip1;1ko) is resistant to toxic concentrations of As[III] but tolerance to arsenite is not due to a reduced uptake through the PM since in two different and independent studies [48,68] nip1;1ko lines were shown to regularly uptake As(III). If nip1;1ko has no effect on As(III) uptake it must control compartmentalization of the metalloid.…”

“…The chemical transformation of the cell wall is anyhow not so important in all those cases where resistant mutants missing some transporters or channels show to recover a normal growth. In the case of As(III) for example, root growth inhibition is not depending on cell wall since the mutant missing one AQP able to transport As (NIP1.1, independent from cell wall deposition or modification), is fully resistant and grows normally [48].…”

Vesicle transport in plants: A revised phylogeny of SNARE proteins

“…SYP51 and SYP52 take part in direct membrane transport from ER to tonoplast and Golgi to mediate vesicle trafficking [76,77]. VAMP714 interacts with SYP121 and SYP22 to mediate vesicle transport from the Golgi apparatus to the vacuole [78,79].…”