The Vacuolar Protein Sorting-38 Subunit of the Arabidopsis Phosphatidylinositol-3-Kinase Complex Plays Critical Roles in Autophagy, Endosome Sorting, and Gravitropism

Abstract

The family of phosphatidylinositols (PtdIns) plays essential roles in membrane identity and intracellular trafficking events. In animals and yeast, PtdIn-3-phosphate, which is particularly important for endosomal sorting, lysosomal/vacuolar transport and autophagy, is assembled by two conserved kinase complexes comprised of the catalytic VACUOLAR PROTEIN SORTING (VPS)-34 subunit, along with VPS15, AUTOPHAGY-RELATED (ATG)-6, and either ATG14 (complex I) or VPS38 (complex II). Here, we describe the Arabidopsis ortholog of VPS38 and show by interaction assays that it assembles into a tetrameric PtdIn-3 kinase complex II. Plants missing VPS38 are viable but have dampened pollen germination and heightened seed abortion, and display a dwarf rosette phenotype, with defects in leaf and vascular development and sucrose sensing. vps38 seeds accumulate irregular protein storage vesicles and suppress processing of storage proteins into their mature forms. Consistent with a role for PtdIn-3-phosphate in autophagy, vps38 mutants are hypersensitive to nitrogen and fixed-carbon starvation and show reduced autophagic transport of cargo into vacuoles. vps38 seedlings also have dampened root gravitropism, which is underpinned by aberrant vectoral auxin transport likely caused by defects in plasma membrane/endosome cycling of the PIN-FORMED family of auxin transporters necessary for asymmetric cell elongation. Collectively, this study places VPS38 and its class-III PtdIn-3 kinase complex at the nexus of numerous endosomal trafficking events important to plant growth and development.

The miRNA-Mediated Post-Transcriptional Regulation of Maize in Response to High Temperature

“…In our study, the upregulated gene (Zm00001d048258) encoding phosphoinositide phosphatase SAC2 was targeted by the downregulated sbi-miR5381_L-1R+3, which indicated that miR5381 is involved in signaling transduction under HT stress. Moreover, another upregulated gene encoding vacuolar protein sorting-associated protein 24 (VPS24) homolog 1 was targeted by the downregulated miRn202 (Table S8) and VPS24 homolog 1 was enriched in vacuolar transport and the endocytosis pathway, which is consistent with a recent report that identified it as one subunit of the Arabidopsis phosphatidylinositol-3-kinase complex, in which the VPS38 plays critical roles in autophagy and endosome sorting [65].…”

Endomembrane Reorganization Induced by Heavy Metals

“…Vacuolar traffic and autophagy are important in homeostasis and detoxification processes but are often interconnected to ER and GA plasticity and involve the formation of the so-called Multi Vesicular Bodies (MVBs) [80][81][82][83][84][85]. A microarray study in Populus stressed by Zn allowed the identification of an AQP of NIP type, AQUA1 [86], down-regulated in both leaf and root tissues, possibly with the effect to reduce transpiration, water/Zn uptake, and leaf growth, probably for protecting photosynthetic tissues and for enhancing poplar tolerance [87].…”

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

“…We suggest that NIP1;1 can increase translocation of As(III), coherently with its localization in the ER, but it has a prominent role in intracellular compartmentalization so that its absence alters the vacuole characteristics and, as a consequence, As(III) tolerance. The different involvement of vacuolar traffic machineries in homeostasis and detoxification processes and the connections with autophagy have been previously studied (Kulich and Žárský, 2014; Sharma et al, 2016; Barozzi et al, 2017; Faraco et al, 2017; Ariani et al, 2018; Liu et al, 2018).…”