title: Trafficking of plant vacuolar invertases: from a membrane-anchored to a soluble status. Understanding sorting information in their complex N-terminal motifs.
abstract: Vacuolar invertases (VIs) are highly expressed in young tissues and organs. They may have a substantial regulatory influence on whole-plant metabolism as well as on photosynthetic efficiency. Therefore, they are emerging as potentially interesting biotechnological targets to increase plant biomass production, especially under stress. On the one hand, VIs are well known as soluble and extractable proteins. On the other hand, they contain complex N-terminal propeptide (NTPP) regions with a basic region (BR) and a transmembrane domain (TMD). Here we analyzed in depth the Arabidopsis thaliana VI2 (AtVI2) NTPP by mutagenesis. It was found that correct sorting to the lytic vacuole (LV) depends on the presence of intact dileucine (SSDALLPIS), BR (RRRR) and TMD motifs. AtVI2 remains inserted into membranes on its way to the LV, and the classical sorting pathway (endoplasmic reticulum→Golgi→LV) is followed. However, our data suggest that VIs might follow an alternative, adaptor protein 3 (AP3)-dependent route as well. Membrane-anchored transport and a direct recognition of the dileucine motif in the NTPP of VIs might have evolved as a simple and more efficient sorting mechanism as compared with the vacuolar sorting receptor 1/binding protein of 80 kDa (VSR1/BP80)-dependent sorting mechanism followed by those proteins that travel to the vacuole as soluble proteins.
authors.affiliation: Biology Department, Laboratory for Molecular Plant Biology, KU Leuven, Kasteelpark Arenberg 31, Box 2434, B-3001 Heverlee, Belgium.
authors.forename: Li
authors.initials: L
authors.lastname: Xiang
authors.forename: Wim
authors.initials: W
authors.lastname: Van den Ende
mesh_terms: D033963:Adaptor Protein Complex 3 / Q000235:genetics / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D004721:Endoplasmic Reticulum / Q000201:enzymology; D055786:Gene Knockout Techniques; D017930:Genes, Reporter; D006056:Golgi Apparatus / Q000201:enzymology; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D018515:Plant Leaves / Q000166:cytology / Q000201:enzymology; D030821:Plants, Genetically Modified; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011993:Recombinant Fusion Proteins; D016415:Sequence Alignment; D014617:Vacuoles / Q000201:enzymology*; D043324:beta-Fructofuranosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D033963:Adaptor Protein Complex 3; D029681:Arabidopsis Proteins; D011993:Recombinant Fusion Proteins; D043324:beta-Fructofuranosidase
keywords: Arabidopsis thaliana; BP80; Invertase; Sorting; Sucrose; Vacuole