Amyloids are protein aggregates with a highly ordered spatial structure giving them unique physicochemical properties. Different amyloids not only participate in the development of numerous incurable diseases but control vital functions in archaea, bacteria and eukarya. Plants are a poorly studied systematic group in the field of amyloid biology. Amyloid properties have not yet been demonstrated for plant proteins under native conditions in vivo. Here we show that seeds of garden pea Pisum sativum L. contain amyloid-like aggregates of storage proteins, the most abundant one, 7S globulin Vicilin, forms bona fide amyloids in vivo and in vitro. Full-length Vicilin contains 2 evolutionary conserved β-barrel domains, Cupin-1.1 and Cupin-1.2, that self-assemble in vitro into amyloid fibrils with similar physicochemical properties. However, Cupin-1.2 fibrils unlike Cupin-1.1 can seed Vicilin fibrillation. In vivo, Vicilin forms amyloids in the cotyledon cells that bind amyloid-specific dyes and possess resistance to detergents and proteases. The Vicilin amyloid accumulation increases during seed maturation and wanes at germination. Amyloids of Vicilin resist digestion by gastrointestinal enzymes, persist in canned peas, and exhibit toxicity for yeast and mammalian cells. Our finding for the first time reveals involvement of amyloid formation in the accumulation of storage proteins in plant seeds.

Bacillus thuringiensis (Bt), a natural pathogen of different invertebrates, primarily insects, is widely used as a biological control agent. While Bt-based preparations are claimed to be safe for non-target organisms due to the immense host specificity of the bacterium, the growing evidence witnesses the distant consequences of their application for natural communities. For instance, upon introduction to soil habitats, Bt strains can affect indigenous microorganisms, such as bacteria and fungi, and further establish complex relationships with local plants, ranging from a mostly beneficial demeanor, to pathogenesis-like plant colonization. By exerting a direct effect on target insects, Bt can indirectly affect other organisms in the food chain. Furthermore, they can also exert an off-target activity on various soil and terrestrial invertebrates, and the frequent acquisition of virulence factors unrelated to major insecticidal toxins can extend the Bt host range to vertebrates, including humans. Even in the absence of direct detrimental effects, the exposure to Bt treatment may affect non-target organisms by reducing prey base and its nutritional value, resulting in delayed alleviation of their viability. The immense phenotypic plasticity of Bt strains, coupled with the complexity of ecological relationships they can engage in, indicates that further assessment of future Bt-based pesticides’ safety should consider multiple levels of ecosystem organization and extend to a wide variety of their inhabitants.

Bacillus thuringiensis (Bt) is a Gram-positive soil bacteria that infects invertebrates, predominantly of Arthropoda phylum. Due to its immense host range Bt has become a leading producer of biopesticides applied both in biotechnology and agriculture. Cytotoxic effect of Bt, as well as its host specificity, are commonly attributed either to proteinaceous crystal parasporal toxins (Cry and Cyt) produced by bacteria in a stationary phase or to soluble toxins of Vip and Sip families secreted by vegetative cells. At the same time, numerous non-toxin virulence factors of Bt have been discovered, including metalloproteases, chitinases, aminopolyol antibiotics and nucleotide-mimicking moieties. These agents act at each stage of the B. thuringiensis invasion and contribute to cytotoxic properties of Bt strains enhancing toxin activity, ensuring host immune response evasion and participating in extracellular matrix degeneration. In this review we attempt to classify Bt virulence factors unrelated to major groups of protein toxins and discuss their putative role in the establishment of Bt specificity to various groups of insects.

Amyloids are unbranched protein fibrils with a characteristic spatial structure. Although the amyloids were first described as protein deposits that are associated with the diseases, today it is becoming clear that these protein fibrils play multiple biological roles that are essential for different organisms, from archaea and bacteria to humans. The appearance of amyloid, first of all, causes changes in the intracellular quantity of the corresponding soluble protein(s), and at the same time the aggregate can include other proteins due to different molecular mechanisms. The co-aggregation may have different consequences even though usually this process leads to the depletion of a functional protein that may be associated with different diseases. The protein co-aggregation that is related to functional amyloids may mediate important biological processes and change of protein functions. In this review, we survey the known examples of the amyloid-related co-aggregation of proteins, discuss their pathogenic and functional roles, and analyze methods of their studies from bacteria and yeast to mammals. Such analysis allow for us to propose the following co-aggregation classes: (i) titration: deposition of soluble proteins on the amyloids formed by their functional partners, with such interactions mediated by a specific binding site; (ii) sequestration: interaction of amyloids with certain proteins lacking a specific binding site; (iii) axial co-aggregation of different proteins within the same amyloid fibril; and, (iv) lateral co-aggregation of amyloid fibrils, each formed by different proteins.

The term "amyloids" refers to fibrillar protein aggregates with cross-β structure. They have been a subject of intense scrutiny since the middle of the previous century. First, this interest is due to association of amyloids with dozens of incurable human diseases called amyloidoses, which affect hundreds of millions of people. However, during the last decade the paradigm of amyloids as pathogens has changed due to an increase in understanding of their role as a specific variant of quaternary protein structure essential for the living cell. Thus, functional amyloids are found in all domains of the living world, and they fulfill a variety of roles ranging from biofilm formation in bacteria to long-term memory regulation in higher eukaryotes. Prions, which are proteins capable of existing under the same conditions in two or more conformations at least one of which having infective properties, also typically have amyloid features. There are weighty reasons to believe that the currently known amyloids are only a minority of their real number. This review provides a retrospective analysis of stages in the development of amyloid biology that during the last decade resulted, on one hand, in reinterpretation of the biological role of amyloids, and on the other hand, in the development of systems biology of amyloids, or amyloidomics.

Amyloids are protein aggregates consisting of fibrils rich in β-sheets. Growth of amyloid fibrils occurs by the addition of protein molecules to the tip of an aggregate with a concurrent change of a conformation. Thus, amyloids are self-propagating protein conformations. In certain cases these conformations are transmissible / infectious; they are known as prions. Initially, amyloids were discovered as pathological extracellular deposits occurring in different tissues and organs. To date, amyloids and prions have been associated with over 30 incurable diseases in humans and animals. However, a number of recent studies demonstrate that amyloids are also functionally involved in a variety of biological processes, from biofilm formation by bacteria, to long-term memory in animals. Interestingly, amyloid-forming proteins are highly overrepresented among cellular factors engaged in all stages of mRNA life cycle: from transcription and translation, to storage and degradation. Here we review rapidly accumulating data on functional and pathogenic amyloids associated with mRNA processing, and discuss possible significance of prion and amyloid networks in the modulation of key cellular functions.