In Vivo Analysis of ER-Associated Protein Degradation and Ubiquitination in Arabidopsis thaliana.

The endoplasmic reticulum (ER) is the cellular site for the biosynthesis of proteins and lipids. The ER is highly dynamic, whose homeostasis is maintained by proper ER shaping, unfolded protein response (UPR), ER-associated degradation (ERAD), and selective autophagy of the ER (ER-phagy). In ERAD and ER-phagy, unfolded/misfolded proteins are degraded in the 26S proteasome and the vacuole, respectively.

RABC1, an Arabidopsis RAB18 regulates binding and subsequent detachment of autophagosomes from the ER in autophagy.

Macroautophagy/autophagy is a strategy cells use to cope with detrimental conditions, e.g. nutrient deficiency.

An Arabidopsis Rab18 GTPase promotes autophagy by tethering ATG18a to the ER in response to nutrient starvation.

The expansion of autophagosomes requires a controlled association with the endoplasmic reticulum (ER). However, the mechanisms governing this process are not well defined. In plants, ATG18a plays a key role in autophagosome formation in response to stress, yet the factors regulating the process are unknown.

Arabidopsis reticulons inhibit ROOT HAIR DEFECTIVE3 to form a stable tubular endoplasmic reticulum network.

The endoplasmic reticulum (ER) is a network of interconnected tubules and sheets stretching throughout the cytoplasm of plant cells. In Arabidopsis (Arabidopsis thaliana), ROOT HAIR DEFECTIVE3 (RHD3) mediates ER tubule fusion, while reticulon proteins induce ER membrane curvature to produce ER tubules. However, it is unclear if and how RHD3-reticulon interplay during the formation of the interconnected tubular ER network.

ROOT HAIR DEFECTIVE3 Is a Receptor for Selective Autophagy of the Endoplasmic Reticulum in .

ROOT HAIR DEFECTIVE3 (RHD3) is a plant member of atlastin GTPases, which belong to an evolutionally conserved family of proteins that mediate the homotypic fusion of the endoplasmic reticulum (ER). An atlastin in mammalian cells has recently been shown to act as an ER-phagy receptor for selective autophagy of the ER (ER-phagy) during nutrient starvation. Although RHD3 has been indicated to play a role in ER stress response, it is not very clear how RHD3 is involved in the process.

Partnership in action: The endoplasmic reticulum regulates the cytoskeleton.

The endoplasmic reticulum (ER) and the cytoskeleton are functionally linked in living cells. Past research has focused on how the cytoskeleton regulates ER dynamics. How the ER may contribute to cytoskeletal dynamics has been overlooked.

Osj10gBTF3-Mediated Import of Chloroplast Protein Is Essential for Pollen Development in Rice.

Chloroplasts are crucial organelles for the generation of fatty acids and starch required for plant development. Nascent polypeptide-associated complex (NAC) proteins have been implicated in development as transcription factors. However, their chaperone roles in chloroplasts and their relationship with pollen development in plants remain to be elucidated.

Armadillo-repeat kinesin1 interacts with Arabidopsis atlastin RHD3 to move ER with plus-end of microtubules.

In living cells, dynamics of the endoplasmic reticulum (ER) are driven by the cytoskeleton motor machinery as well as the action of ER-shaping proteins such as atlastin GTPases including RHD3 in Arabidopsis. It is not known if the two systems interplay, and, if so, how they do. Here we report the identification of ARK1 (Armadillo-Repeat Kinesin1) via a genetic screen for enhancers of the rhd3 mutant phenotype.

A Poplar Rust Effector Protein Associates with Protein Disulfide Isomerase and Enhances Plant Susceptibility.

, the causal agent of leaf rust, secretes an array of effectors into the host through the haustorium to gain nutrients and suppress immunity. The precise mechanisms by which these effectors promote virulence remain unclear. To address this question, we developed a transgenic line expressing a candidate effector, Mlp124357.

LUNAPARK Is an E3 Ligase That Mediates Degradation of ROOT HAIR DEFECTIVE3 to Maintain a Tubular ER Network in Arabidopsis.

ROOT HAIR DEFECTIVE3 (RHD3) is an atlastin GTPase involved in homotypic fusion of endoplasmic reticulum (ER) tubules in the formation of the interconnected ER network. Because excessive fusion of ER tubules will lead to the formation of sheet-like ER, the action of atlastin GTPases must be tightly regulated. We show here that RHD3 physically interacts with two Arabidopsis () LUNAPARK proteins, LNP1 and LNP2, at three-way junctions of the ER, the sites where different ER tubules fuse.

An essential role for Arabidopsis Trs33 in cell growth and organization in plant apical meristems.

Trafficking protein particle (TRAPP) complexes subunit gene AtTrs33 plays an important role in keeping apical meristematic activity and dominance in Arabidopsis. TRAPP complexes, composed of multimeric subunits, are guanine-nucleotide exchange factors for certain Rab GTPases and are believed to be involved in the regulation of membrane trafficking, but the cases in Arabidopsis are largely unknown. Trs33, recently proposed to be a component of TRAPP IV, is non-essential in yeast cells.

Vacuolar membrane structures and their roles in plant-pathogen interactions.

Short review focussing on the role and targeting of vacuolar substructure in plant immunity and pathogenesis. Plants lack specialized immune cells, therefore each plant cell must defend itself against invading pathogens. A typical plant defense strategy is the hypersensitive response that results in host cell death at the site of infection, a process largely regulated by the vacuole.

ECERIFERUM11/C-TERMINAL DOMAIN PHOSPHATASE-LIKE2 Affects Secretory Trafficking.

Secretory trafficking is highly conserved in all eukaryotic cells and is required for secretion of proteins as well as extracellular matrix components. In plants, the export of cuticular waxes and various cell wall components relies on secretory trafficking, but the molecular mechanisms underlying their secretion are not well understood. In this study, we characterize the Arabidopsis () dwarf () mutant and we show that it exhibits reduced stem cuticular wax deposition, aberrant seed coat mucilage extrusion, and delayed secondary cell wall columella formation, as well as a block in secretory GFP trafficking.

Interactions between Transport Protein Particle (TRAPP) complexes and Rab GTPases in Arabidopsis.

Transport Protein Particle II (TRAPPII) is essential for exocytosis, endocytosis, protein sorting and cytokinesis. In spite of a considerable understanding of its biological role, little information is known about Arabidopsis TRAPPII complex topology and molecular function. In this study, independent proteomic approaches initiated with TRAPP components or Rab-A GTPase variants converge on the TRAPPII complex.

Turnip Mosaic Virus Components Are Released into the Extracellular Space by Vesicles in Infected Leaves.

Turnip mosaic virus (TuMV) reorganizes the endomembrane system of the infected cell to generate endoplasmic-reticulum-derived motile vesicles containing viral replication complexes. The membrane-associated viral protein 6K plays a key role in the formation of these vesicles. Using confocal microscopy, we observed that this viral protein, a marker for viral replication complexes, localized in the extracellular space of infected leaves.

A Host ER Fusogen Is Recruited by for Maturation of Viral Replication Vesicles.

Like other positive-strand RNA viruses, the (TuMV) infection leads to the formation of viral vesicles at the endoplasmic reticulum (ER). Once released from the ER, the viral vesicles mature intracellularly and then move intercellularly. While it is known that the membrane-associated viral protein 6K2 plays a role in the process, the contribution of host proteins has been poorly defined.

Turnip Mosaic Virus Uses the SNARE Protein VTI11 in an Unconventional Route for Replication Vesicle Trafficking.

Infection of plant cells by RNA viruses leads to the generation of organelle-like subcellular structures that contain the viral replication complex. During (TuMV) infection of , the viral membrane protein 6K plays a key role in the release of motile replication vesicles from the host endoplasmic reticulum (ER). Here, we demonstrate that 6K contains a GxxxG motif within its predicted transmembrane domain that is vital for TuMV infection.

AtBET5 is essential for exine pattern formation and apical meristem organization in Arabidopsis.

BET5 is a component of trafficking protein particle (TRAPP) which has been studied extensively in non-plant organisms where they are involved in membrane trafficking within Golgi and between Golgi and early endosomes. Recent analysis of TRAPP in different classes of organisms indicates that TRAPP function might exhibit differences among organisms. A single copy of the BET5 gene named AtBET5 was found in the Arabidopsis genome based on sequence similarity.

Characterization of the Populus Rab family genes and the function of PtRabE1b in salt tolerance.

Background: Rab proteins form the largest family of the Ras superfamily of small GTP-binding proteins and regulate intracellular trafficking pathways. However, the function of the Rab proteins in woody species is still an open question.

Results: Here, a total of 67 PtRabs were identified in Populus trichocarpa and categorized into eight subfamilies (RabA-RabH).

Efficient ER Fusion Requires a Dimerization and a C-Terminal Tail Mediated Membrane Anchoring of RHD3.

The endoplasmic reticulum (ER) is a network of tubules and sheets stretching throughout the eukaryotic cells. The formation of the ER requires homotypic membrane fusion, which is mediated by a family of Dynamin-like Atlastin GTPase proteins. The Arabidopsis () member ROOT HAIR DEFECTIVE3 (RHD3) has been demonstrated to mediate ER membrane fusion, but how exactly RHD3 is involved in the process is still unknown.

Cylindrical Inclusion Protein of Turnip Mosaic Virus Serves as a Docking Point for the Intercellular Movement of Viral Replication Vesicles.

Plant viruses move from the initially infected cell to adjacent cells through plasmodesmata (PDs). To do so, viruses encode dedicated protein(s) that facilitate this process. How viral proteins act together to support the intercellular movement of viruses is poorly defined.

Identification of microRNAs Involved in Regeneration of the Secondary Vascular System in Populus tomentosa Carr.

Wood formation is a complex developmental process primarily controlled by a regulatory transcription network. MicroRNAs (miRNAs) can modulate the expression of target genes involved in plant growth and development by inducing mRNA degradation and translational repression. In this study, we used a model of secondary vascular system regeneration established in Populus tomentosa to harvest differentiating xylem tissues over time for high-throughput sequencing of small RNAs.

A GTPase-Dependent Fine ER Is Required for Localized Secretion in Polarized Growth of Root Hairs1.

The endoplasmic reticulum (ER) is a cellular network comprising membrane tubules and sheets stretching throughout the cytoplasm. Atlastin GTPases, including Atlastin-1 in mammals and RHD3 in plants, play a role in the generation of the interconnected tubular ER network by promoting the fusion of ER tubules. Root hairs in rhd3 are short and wavy, a defect reminiscent of axon growth in cells with depleted Atlastin-1.

An Integrated Bioinformatics Analysis Reveals Divergent Evolutionary Pattern of Oil Biosynthesis in High- and Low-Oil Plants.

Seed oils provide a renewable source of food, biofuel and industrial raw materials that is important for humans. Although many genes and pathways for acyl-lipid metabolism have been identified, little is known about whether there is a specific mechanism for high-oil content in high-oil plants. Based on the distinct differences in seed oil content between four high-oil dicots (20~50%) and three low-oil grasses (<3%), comparative genome, transcriptome and differential expression analyses were used to investigate this mechanism.