Biology subjects

Moschou, P. N.

Publications and source records attributed to Moschou, P. N..

7 recordsLinked to original sources

bioRxiv2026

Starvation-induced autophagy occurs independently of the ATG1 complex in Chlamydomonas

The survival of eukaryotes during starvation depends on effective nutrient recycling via autophagy. Accordingly, loss of autophagy-related (ATG) proteins, including the nutrient-sensing ATG1 kinase complex, typically results in reduced fitness or lethality under nutrient limitation. The green alga Chlamydomonas reinhardtii provides a tractable model for autophagy studies, as its ATG repertoire is encoded by single-copy genes. Here, we generated a comprehensive library of ATG deletion mutants and examined their growth and autophagy during starvation. Surprisingly, starvation-induced autophagy occurred in the absence of ATG1 complex components (ATG1, ATG11, ATG13, and ATG101), revealing ATG1-independent autophagy and challenging the canonical model for autophagy initiation.

molecular biology↗

bioRxiv2023

A Proxitome-RNA-capture Approach Reveals that Processing Bodies Repress Co-Regulated Hubs

Cellular condensates are usually ribonucleoprotein assemblies with liquid- or solid-like properties. Because they lack a delineating membrane, the compositional determination of condensates is laborious. Here we set up a pipeline for proximity-biotinylation-dependent capture of RNA to investigate the RNA composition of the condensate in Arabidopsis known as the processing bodies (PBs). Using this pipeline together with in situ protein-protein interaction and RNA detection, in silico, and high-resolution imaging approaches, we studied PBs under normal and heat stress conditions. The composition of PBs in RNAs is much more dynamic than that of the total transcriptome. RNAs involved in cell wall development and regeneration, hormonal signaling, secondary metabolism/defense, and RNA metabolism were enriched in PBs. RNA binding proteins and liquid-to-solid phase transitions modulated specificity of RNA recruitment in PBs. Surprisingly, RNAs were sometimes recruited together with their encoded proteins. In PBs RNAs follow distinct fates, with small liquid-like PBs modulating RNA decay while larger ones storage. The size and properties of PBs are regulated by the actin polymerization cAMP receptor (SCAR)-WASP family verprolin homologous (WAVE) complex. SCAR/WAVE modulates signaling by shuttling RNAs between PBs and the translational machinery adjusting the ethylene signaling pathway. Heat stress leads to the storage of immunity-related RNAs in PBs by reducing PBs dynamics, suggesting why processes such as immunity malfunction under heat stress. In summary, we provide a method to identify RNAs in condensates which allowed us to reveal a mechanism for RNA fate regulation.

plant biology↗

bioRxiv2023

Seed Longevity is Controlled by Metacaspases

To survive extreme desiccation, seeds enter dormancy that can last millennia. This dormancy involves the accumulation of protective but structurally disordered storage proteins through unknown adjustments of proteolytic surveillance mechanisms. Mutation of all six types II metacaspases (MCAs)-II in the model plant Arabidopsis revealed their essential role in modulating these proteolytic mechanisms. MCA-II mutant seeds fail to properly target at the endoplasmic reticulum (ER) the AAA ATPase Cell Division Cycle 48 (CDC48) to dispose of misfolded proteins. MCA-IIs cleave a CDC48 adaptor, the ubiquitination regulatory X domain-containing (PUX) responsible for localizing CDC48 to the lipid droplets. When cleaved, CDC48-PUX is inactivated and allows a lipid droplet-to-ER shuttling of CDC48, an important step in the regulation of seeds lifespan. In sum, we uncover antagonism between proteolytic pathways bestowing longevity. One-Sentence SummaryMetacaspase proteases confer seed longevity by antagonizing CDC48 activity.

plant biology↗

bioRxiv2022

The Proxitome of Arabidopsis Processing Bodies Reveals a Condensate-Membrane Interface Instructing Actin-Driven Directional Growth

Cellular condensates can comprise membrane-less ribonucleoprotein assemblies with liquid-like properties. These cellular condensates influence various biological outcomes, but their liquidity hampers their isolation and characterization. Here, we investigated the composition of the condensates known as processing bodies (PBs) in the model plant Arabidopsis through a proximity-biotinylation pipeline. Using in situ protein-protein interaction approaches, genetics and high-resolution imaging, we show that PBs comprise networks that interface with membranes. Surprisingly, the conserved component of PBs, DECAPPING PROTEIN 1 (DCP1), can interface with unique plasma membrane subdomains that include cell edges and vertices. We characterized these plasma membrane interfaces and discovered a developmental module that can control cell shape. This module is modulated by the liquid-like properties of DCP1 and the actin-nucleating SCAR-WAVE complex, whereby the DCP1-SCAR-WAVE interaction confines actin nucleation. This study reveals an unexpected repertoire for a conserved condensate at unique membrane-condensate interfaces.

cell biology↗

bioRxiv2022

Phase Separation of a Nodulin Sec14-like protein Maintains Auxin Efflux Carrier Polarity at Arabidopsis Plasma Membranes

Protein function can be modulated by phase transitions in their material properties, which can range from liquid-to solid-like; yet the mechanisms that drive these transitions and whether they are important for physiology are still unknown. Using the model plant Arabidopsis, we show that developmental robustness is reinforced by phase transitions of the plasma membrane-bound lipid-binding protein SEC14-like. Using imaging, genetics, and in vitro reconstitution experiments, we show that SEC14-like undergoes liquid-like phase separation in the root stem cells. Outside the stem cell niche, SEC14-like associates with the caspase-like protease separase and conserved microtubule motors at unique polar plasma membrane interfaces. In these interfaces, SEC14-like undergoes abrupt processing by separase, which promotes its liquid-to-solid transition. The SEC14-like liquid-to-solid transition is important for root developmental robustness, as lines expressing an uncleavable SEC14-like variant or mutants of separase, and associated microtubule motors show similar developmental phenotypes. Furthermore, the processed and solidified but not the liquid form of SEC14-like interacts with the polar protein PINFORMED2 at the plasma membrane and perhaps other polar proteins of the PINFORMED family. This work demonstrates that robust development can involve abrupt liquid-to-solid transitions mediated by proteolysis at unique plasma membrane interfaces.

cell biology↗

bioRxiv2021

DNA Preparation In Vitis vinifera L. For Third Generation Sequencing

BackgroundThere have been several attempts to sequence the genome of Vitis vinifera L. (grapevine), utilizing low-resolution second-generation platforms. Nevertheless, the characterization of the grapevine genetic resources and its adaptation to vulnerable conditions could be better addressed through extensive and high-resolution genome sequencing. MinION is a third-generation sequencer preferred by many laboratories due to its relatively low cost, ease of use and small size. Even though this long-read technology has been rapidly improving, to reach its full potential requires high-quality DNA. ResultsHere we establish a workflow for DNA extraction suitable for MinION sequencing long reads from grapevine. This protocol was tested with leaf samples from different positions on annual growing branches of grapevine, Purified nuclei from fresh young leaves that led to high quality, long DNA fragments, suitable for long-read sequencing were successfully generated. It is evident that longer reads in grapevine associate with both fresh tissue and adjusted conditions used for nuclei purification. ConclusionsWe propose that this workflow presents a significant advancement for long-read quality DNA isolation for grapevine and likely other plant species.

genomics↗

bioRxiv2020

Tudor staphylococcal nuclease acts as a docking platform for stress granule components in Arabidopsis thaliana

Adaptation to stress depends on the modulation of gene expression. Regulation of mRNA stability and degradation in stress granules (SGs), - cytoplasmic membraneless organelles composed of messenger ribonucleoprotein (mRNP) complexes, - plays an important role in fine-tuning of gene expression. In addition, SG formation can modulate stress signaling pathways by protein sequestration. Molecular composition, structure, and function of SGs in plants remain obscure. Recently, we established Tudor Staphylococcal Nuclease (TSN or Tudor-SN; also known as SND1) as integral component of SGs in Arabidopsis thaliana. Here, we combined purification of TSN interactome with cell biology, reverse genetics and bioinformatics to study composition and function of SGs in plants. We found that under both normal (in the absence of stress) and stress conditions TSN interactome is enriched in the homologues of known mammalian and yeast SG proteins, in addition to novel or plant-specific SG components. We estimate that upon stress perception, approximately half of TSN interactors are recruited to SGs de novo, in a stress-dependent manner, while another half represent a dense protein-protein interaction network pre-formed before onset of stress. Almost all TSN-interacting proteins are moderately or highly disordered and approximately 20% of them are predisposed for liquid-liquid phase separation (LLPS). This suggests that plant SGs, similarly to mammalian and yeast counterparts, are multicomponent viscous liquid droplets. Finally, we have discovered that evolutionary conserved SNF1-related protein kinase 1 (SnRK1) interacts with TSN in heat-induced SGs and that SnRK1 activation critically depends on the presence of TSN and formation of SGs. Altogether, our results establish TSN as a docking platform for SG-associated proteins and important stress signal mediator in plants.

plant biology↗