Arabidopsis VPS35, a Retromer Component, is Required for Vacuolar Protein Sorting and Involved in Plant Growth and Leaf Senescence

Abstract

The retromer complex is responsible for retrograde transport, which is coordinated with anterograde transport in the secretory pathway including vacuolar protein sorting. Yeast VPS35 is a component of the retromer complex that is essential for recognition of specific cargo molecules. The physiological function of VPS35 has not been determined in vacuolar protein sorting in higher organisms. Arabidopsis thaliana has three VPS35 homologs designated VPS35a, VPS35b and VPS35c. We isolated four vps35 mutants (vps35a-1, vps35b-1, vps35b-2 and vps35c-1) and then generated four double mutants and one triple mutant. vps35a-1 vps35c-1 exhibited no unusual phenotypes. On the other hand, vps35b-1 vps35c-1 and the triple mutant (vps35a-1 vps35b-2 vps35c-1) exhibited severe phenotypes: dwarfism, early leaf senescence and fragmentation of protein storage vacuoles (PSVs). In addition, these mutants mis-sorted storage proteins by secreting them out of the cells and accumulated a higher level of vacuolar sorting receptor (VSR) than the wild type. VPS35 was localized in pre-vacuolar compartments (PVCs), some of which contained VSR. VPS35 was immunoprecipitated with VPS29/MAG1, another component of the retromer complex. Our findings suggest that VPS35, mainly VPS35b, is involved in sorting proteins to PSVs in seeds, possibly by recycling VSR from PVCs to the Golgi complex, and is also involved in plant growth and senescence in vegetative organs.

ENDOSOMAL RAB EFFECTOR WITH PX-DOMAIN, an Interacting Partner of RAB5 GTPases, Regulates Membrane Trafficking to Protein Storage Vacuoles in Arabidopsis

“…Many mutants with similar phenotypes have been reported thus far, including mutants of vacuolar sorting receptors, vacuolar processing enzymes, and machinery components of membrane trafficking (Shimada et al, 2003a(Shimada et al, , 2003bTamura et al, 2007;Yamazaki et al, 2008;Ebine et al, 2008Ebine et al, , 2014Takahashi et al, 2010;Contento and Bassham, 2012;Shirakawa et al, 2014;Gao et al, 2015;Reguera Teh et al, 2015). In these mutants, the accumulation of unprocessed precursors is also observed for 2S albumin, a major storage protein in Arabidopsis seeds.…”

The role of vacuole in plant cell death

“…However, recent studies suggest that both types of vacuoles share machinery for the intracellular trafficking of vacuolar proteins. 2,3 Most vacuolar soluble proteins are synthesized on the endoplasmic reticulum as larger precursors and then transported into vacuoles, where precursor proteins are converted into their respective mature forms by vacuolar processing enzyme (VPE). [4][5][6][7][8] The machinery in plant cells is used to accumulate a variety of proteins in both types of vacuoles, hydrolytic enzymes including aspartate proteinases, 9 cysteine proteinases, 10,11 and nucleases 12 required for non-selective degradation of cellular components during programmed cell death (PCD), and defense proteins including pathogenesisrelated proteins (PR proteins), 13 myrosinases, 14 toxic proteins, 15 and lectins 16,17 for defense against invading pathogens.…”

GLUTELIN PRECURSOR ACCUMULATION3Encodes a Regulator of Post-Golgi Vesicular Traffic Essential for Vacuolar Protein Sorting in Rice Endosperm

“…Thus, the DV defines a unique carrier for trafficking of storage proteins to the PSV. Growing evidence is showing that post-Golgi trafficking of storage proteins to the PSV also requires the retromer components (MAG1/VPS29, VPS35, and SNXs) involved in the recycling of VSRs (Shimada et al, 2003(Shimada et al, , 2006Yamazaki et al, 2008;Zouhar et al, 2009;Pourcher et al, 2010), the Rab family of small GTPases as well as their common guanine exchange factor (GEF) for specifying vesicular trafficking (Wang et al, 2010;Ebine et al, 2011;Liu et al, 2013), and the SNARE complex for mediating membrane fusion between post-Golgi compartments (Ebine et al, 2008). However, plantspecific regulators required for these processes largely remain to be identified.…”