It is known that extracellular vesicles (EVs) are shed from cells of almost every type of cell or organism, showing their ubiquity in all empires of life. EVs are defined as naturally released particles from cells, delimited by a lipid bilayer, and cannot replicate. These nano- to micrometer scaled spheres shuttle a set of bioactive molecules. EVs are of great interest as vehicles for drug targeting and in fundamental biological research, but in vitro culture of animal cells usually achieves only small yields. The exploration of other biological kingdoms promises comprehensive knowledge on EVs broadening the opportunities for basic understanding and therapeutic use. Thus, plants might be sustainable biofactories producing nontoxic and highly specific nanovectors, whereas bacterial and fungal EVs are promising vaccines for the prevention of infectious diseases. Importantly, EVs from different eukaryotic and prokaryotic kingdoms are involved in many processes including host-pathogen interactions, spreading of resistances, and plant diseases. More extensive knowledge of inter-species and interkingdom regulation could provide advantages for preventing and treating pests and pathogens. In this review, we present a comprehensive overview of EVs derived from eukaryota and prokaryota and we discuss how better understanding of their intercommunication role provides opportunities for both fundamental and applied biology.

While human extracellular vesicles (EVs) have attracted a big deal of interest and have been extensively characterized over the last years, plant-derived EVs and nanovesicles have earned less attention and have remained poorly investigated. Although a series of investigations already revealed promising beneficial health effects and drug delivery properties, adequate (pre)clinical studies are rare. This fact might be caused by a lack of sources with appropriate qualities. Our study introduces plant cell suspension culture as a new and well controllable source for plant EVs. Plant cells, cultured in vitro, release EVs into the growth medium which could be harvested for pharmaceutical applications. In this investigation we characterized EVs and nanovesicles from distinct sources. Our findings regarding secondary metabolites indicate that these might not be packaged into EVs in an active manner but enriched in the membrane when lipophilic enough, since apparently lipophilic compounds were associated with nanovesicles while more hydrophilic structures were not consistently found. In addition, protein identification revealed a possible explanation for the mechanism of EV cell wall passage in plants, since cell wall hydrolases like 1,3-β-glucosidases, pectinesterases, polygalacturonases, β-galactosidases and β-xylosidase/α-L-arabinofuranosidase 2-like are present in plant EVs and nanovesicles which might facilitate cell wall transition. Further on, the identified proteins indicate that plant cells secrete EVs using similar mechanisms as animal cells to release exosomes and microvesicles.

Although animal-derived extracellular vesicles (EVs) are moving increasingly into scientific focus, EVs from other kingdoms remain underestimated and our knowledge of them is still expandable, probably due to the lack of an easy and broadly executable isolation, purification and visualization method. Using differential centrifugation with subsequent agarose gel electrophoresis, we were able to simplify the terms of EV isolation. EVs from Nicotiana tabacum L., Vinca minor L., and Viscum album L. were purified, even though they did not migrate into the gel matrix. If 3,3- Dihexyloxacarbocyanine iodide (DiOC ${}_6$ ) is added to the specimen in excess, membranous components can already be detected by eye, or with higher sensitivity, using a UV transilluminator. The sample preparation can be adjusted to the EV species of interest. Moreover, EVs are separated from small charged contaminants and dye excess, because these impurities can pass the gel matrix, while EVs themselves are retained in the pocket. Significantly, we isolated EVs from dried plant material, which is—to our knowledge—the first proof that EVs are stable enough to overcome the drying process of plant material.