Extracellular vesicles in phytopathogenic fungi

Establishment of an experimental system to analyse extracellular vesicles during apoplastic fungal pathogenesis

Phoma stem canker disease of oilseed rape (Brassica napus) is caused by the extracellular fungal pathogen Leptosphaeria maculans. Although this pathogen resides exclusively in apoplastic spaces surrounding plant cells, the significance of extracellular vesicles (EVs) has not been assessed. Here, we show a method to collect apoplastic fluids (AFs) from infected leaves or cotyledons for collection of EVs during the process of host colonisation. The 15,000 × g supernatants of AFs were shown to contain ribulose-bisphosphate carboxylase (RuBisCO) at 7 days post-inoculation with L. maculans, a protein that was absent from unchallenged cotyledons. RuBisCO release coincided with the switch from biotrophy to necrotrophy, suggesting the involvement of host cell death. However, RuBisCO release did not differ between compatible and incompatible interactions, suggesting necrotrophic host cell death might not be the only process involved. EVs were also collected from axenic fungal cultures and characterised for their particle size distribution using nanoparticle tracking analysis and transmission electron microscopy. The protein composition of EV-enriched fractions was analysed using SDS-PAGE and proteomics. Enrichment analysis of gene ontology terms provided evidence for involvement of glucan and chitin metabolism as well as catalase and peptidase activities. Most of the proteins identified have previously been found in EV studies and/or EV databases, and for most of the proteins evidence was found for an involvement in pathogenicity/virulence.

The pharmacodynamic and pharmacological mechanisms underlying nanovesicles of natural products: Developments and challenges

Natural products such as Traditional Chinese Medicines (TCMs) show great advantages in the treatment and prevention of diseases, but the unclear effective ingredients and mechanisms are key obstacles to restrict their rapid development. Under the guidance of the theoretical guidance of reductionism and the theoretical of allopathic medicine, some researches have indeed achieved some breakthrough results. However, these incomplete methods mainly limited to direct actions or indirect actions (such as the intermediated substances mediated cross-organ or cross-system regulation) mechanism of single active ingredient derived from natural products, which are often inconsistent with Systemism and Harmonizing Medicine and make it difficult to reasonably explain the pharmacodynamics and pharmacological mechanism of most natural products. Actually, effective pharmaceutical ingredients often do not exist in the form of free monomers, but prefer to assembly nanovesicles (NVs) for a combinational pharmacological effect, mainly including self-assembled nanoparticles (SANs) and exosome-like nanoparticles (ELNs). These developments of NVs-based application are a good supplement to existing pharmacological mechanism research. Hence, this review focuses on the developments and strategies of the pharmacodynamics and pharmacological mechanism of NVs-based TCMs under the combining theory of traditional Chinese and western medicine. On this basis, a novel "multidimensional combination" research approach is proposed firstly, which will provide new strategies and directions for breaking through the bottleneck of pharmacological mechanism research, and promote the clinical application of innovative natural products including TCMs.

Roadmap to Success: How Oomycete Plant Pathogens Invade Tissues and Deliver Effectors

Filamentous plant pathogens threaten global food security and ecosystem resilience. In recent decades, significant strides have been made in deciphering the molecular basis of plant-pathogen interactions, especially the interplay between pathogens' molecular weaponry and hosts' defense machinery. Stemming from interdisciplinary investigations into the infection cell biology of filamentous plant pathogens, recent breakthrough discoveries have provided a new impetus to the field. These advances include the biophysical characterization of a novel invasion mechanism (i.e., naifu invasion) and the unraveling of novel effector secretion routes. On the plant side, progress includes the identification of components of cellular networks involved in the uptake of intracellular effectors. This exciting body of research underscores the pivotal role of logistics management by the pathogen throughout the infection cycle, encompassing the precolonization stages up to tissue invasion. More insight into these logistics opens new avenues for developing environmentally friendly crop protection strategies in an era marked by an imperative to reduce the use of agrochemicals.

Sorghum bicolor Extracellular Vesicle Isolation, Labeling, and Correlative Light and Electron Microscopy

Extracellular vesicles are membrane-bound organelles that play crucial roles in intercellular communication and elicit responses in the recipient cell, such as defense responses against pathogens. In this study, we have optimized a protocol for isolating extracellular vesicles (EVs) from Sorghum bicolor apoplastic wash. We characterized the EVs using fluorescence microscopy and correlative light and electron microscopy. Key features • Allows the isolation of extracellular vesicles from the monocot plant Sorghum bicolor. • Labels isolated extracellular vesicles with fluorescent dyes for easy characterization with light microscopy. • Validates dye labeling and further characterizes extracellular vesicles using a correlative light and electron microscopy approach.

Distribution and Implications of Haloarchaeal Plasmids Disseminated in Self-Encoded Plasmid Vesicles

Even though viruses and plasmids are both drivers of horizontal gene transfer, they differ fundamentally in their mode of transfer. Virus genomes are enclosed in virus capsids and are not dependent on cell-to-cell contacts for their dissemination. In contrast, the transfer of plasmids most often requires physical contact between cells. However, plasmid pR1SE of Halorubrum lacusprofundi is disseminated between cells, independent of cell-cell contacts, in specialized membrane vesicles that contain plasmid proteins. In this study, we searched for pR1SE-like elements in public databases and a metagenomics dataset from Australian salt lakes and identified 40 additional pR1SE-like elements in hypersaline environments worldwide. Herein, these elements are named apHPVs (archaeal plasmids of haloarchaea potentially transferred in plasmid vesicles). They share two sets of closely related proteins with conserved synteny, strongly indicating an organization into different functional clusters. We find that apHPVs, besides transferring themselves, have the potential to transfer large fragments of DNA between host cells, including virus defense systems. Most interestingly, apHPVs likely play an important role in the evolution of viruses and plasmids in haloarchaea, as they appear to recombine with both of them. This further supports the idea that plasmids and viruses are not distinct but closely related mobile genetic elements.

Fungal small RNAs ride in extracellular vesicles to enter plant cells through clathrin-mediated endocytosis

Small RNAs (sRNAs) of the fungal pathogen Botrytis cinerea can enter plant cells and hijack host Argonaute protein 1 (AGO1) to silence host immunity genes. However, the mechanism by which these fungal sRNAs are secreted and enter host cells remains unclear. Here, we demonstrate that B. cinerea utilizes extracellular vesicles (EVs) to secrete Bc-sRNAs, which are then internalized by plant cells through clathrin-mediated endocytosis (CME). The B. cinerea tetraspanin protein, Punchless 1 (BcPLS1), serves as an EV biomarker and plays an essential role in fungal pathogenicity. We observe numerous Arabidopsis clathrin-coated vesicles (CCVs) around B. cinerea infection sites and the colocalization of B. cinerea EV marker BcPLS1 and Arabidopsis CLATHRIN LIGHT CHAIN 1, one of the core components of CCV. Meanwhile, BcPLS1 and the B. cinerea-secreted sRNAs are detected in purified CCVs after infection. Arabidopsis knockout mutants and inducible dominant-negative mutants of key components of the CME pathway exhibit increased resistance to B. cinerea infection. Furthermore, Bc-sRNA loading into Arabidopsis AGO1 and host target gene suppression are attenuated in those CME mutants. Together, our results demonstrate that fungi secrete sRNAs via EVs, which then enter host plant cells mainly through CME.