SGnn: A Web Server for the Prediction of Prion-Like Domains Recruitment to Stress Granules Upon Heat Stress

catGRANULE 2.0: accurate predictions of liquid-liquid phase separating proteins at single amino acid resolution

Liquid-liquid phase separation (LLPS) enables the formation of membraneless organelles, essential for cellular organization and implicated in diseases. We introduce catGRANULE 2.0 ROBOT, an algorithm integrating physicochemical properties and AlphaFold-derived structural features to predict LLPS at single-amino-acid resolution. The method achieves high performance and reliably evaluates mutation effects on LLPS propensity, providing detailed predictions of how specific mutations enhance or inhibit phase separation. Supported by experimental validations, including microscopy data, it predicts LLPS across diverse organisms and cellular compartments, offering valuable insights into LLPS mechanisms and mutational impacts. The tool is freely available at https://tools.tartaglialab.com/catgranule2 and https://doi.org/10.5281/zenodo.14205831 .

Rational Tuning of the Concentration-independent Enrichment of Prion-like Domains in Stress Granules

Stress granules (SGs) are large ribonucleoprotein assemblies that form in response to acute stress in eukaryotes. SG formation is thought to be initiated by liquid-liquid phase separation (LLPS) of key proteins and RNA. These molecules serve as a scaffold for recruitment of client molecules. LLPS of scaffold proteins in vitro is highly concentration-dependent, yet biomolecular condensates in vivo contain hundreds of unique proteins, most of which are thought to be clients rather than scaffolds. Many proteins that localize to SGs contain low-complexity, prion-like domains (PrLDs) that have been implicated in LLPS and SG recruitment. The degree of enrichment of proteins in biomolecular condensates such as SGs can vary widely, but the underlying basis for these differences is not fully understood. Here, we develop a toolkit of model PrLDs to examine the factors that govern efficiency of PrLD recruitment to stress granules. Recruitment was highly sensitive to amino acid composition: enrichment in SGs could be tuned through subtle changes in hydrophobicity. By contrast, SG recruitment was largely insensitive to PrLD concentration at both a population level and single-cell level. These observations point to a model wherein PrLDs are enriched in SGs through either simple solvation effects or interactions that are effectively non-saturable even at high expression levels.

In silico analysis of fungal prion-like proteins for elucidating their role in plant-fungi interactions

Prion-like proteins (PrLPs) have emerged as beneficial molecules with implications in adaptive responses. These proteins possess a conserved prion-like domain (PrLD) which is an intrinsically disordered region capable of adopting different conformations upon perceiving external stimuli. Owing to changes in protein conformation, functional characteristics of proteins harboring PrLDs get altered thereby, providing a unique mode of protein-based regulation. Since PrLPs are ubiquitous in nature and involved in diverse functions, through this study, we aim to explore the role of such domains in yet another important physiological process viz. plant-microbe interactions to get insights into the mechanisms dictating cross-kingdom interactions. We have evaluated the presence and functions of PrLPs in 18 different plant-associated fungi of agricultural importance to unravel their role in plant-microbe interactions. Of the 241,997 proteins scanned, 3,820 (~ 1.6%) were identified as putative PrLPs with pathogenic fungi showing significantly higher PrLP density than their beneficial counterparts. Further, through GO enrichment analysis, we could predict several PrLPs from pathogenic fungi to be involved in virulence and formation of stress granules. Notably, PrLPs involved in (retro)transposition were observed exclusively in pathogenic fungi. We even analyzed publicly available data for the expression alterations of fungal PrLPs upon their interaction with their respective hosts which revealed perturbation in the levels of some PrLP-encoding genes during interactions with plants. Overall, our work sheds light into the probable role of prion-like candidates in plant-fungi interaction, particularly in context of pathogenesis, paving way for more focused studies for validating their role.

Liquid-liquid phase separation in plants: Advances and perspectives from model species to crops

Membraneless biomolecular condensates play important roles in both normal biological activities and responses to environmental stimuli in living organisms. Liquid‒liquid phase separation (LLPS) is an organizational mechanism that has emerged in recent years to explain the formation of biomolecular condensates. In the past decade, advances in LLPS research have contributed to breakthroughs in disease fields. By contrast, although LLPS research in plants has progressed over the past 5 years, it has been concentrated on the model plant Arabidopsis, which has limited relevance to agricultural production. In this review, we provide an overview of recently reported advances in LLPS in plants, with a particular focus on photomorphogenesis, flowering, and abiotic and biotic stress responses. We propose that many potential LLPS proteins also exist in crops and may affect crop growth, development, and stress resistance. This possibility presents a great challenge as well as an opportunity for rigorous scientific research on the biological functions and applications of LLPS in crops.

Phase separations in oncogenesis, tumor progressions and metastasis: a glance from hallmarks of cancer

Liquid-liquid phase separation (LLPS) is a novel principle for interpreting precise spatiotemporal coordination in living cells through biomolecular condensate (BMC) formation via dynamic aggregation. LLPS changes individual molecules into membrane-free, droplet-like BMCs with specific functions, which coordinate various cellular activities. The formation and regulation of LLPS are closely associated with oncogenesis, tumor progressions and metastasis, the specific roles and mechanisms of LLPS in tumors still need to be further investigated at present. In this review, we comprehensively summarize the conditions of LLPS and identify mechanisms involved in abnormal LLPS in cancer processes, including tumor growth, metastasis, and angiogenesis from the perspective of cancer hallmarks. We have also reviewed the clinical applications of LLPS in oncologic areas. This systematic summary of dysregulated LLPS from the different dimensions of cancer hallmarks will build a bridge for determining its specific functions to further guide basic research, finding strategies to intervene in LLPS, and developing relevant therapeutic approaches.

Exploring cryptic amyloidogenic regions in prion-like proteins from plants

Prion-like domains (PrLDs) are intrinsically disordered regions (IDRs) of low sequence complexity with a similar composition to yeast prion domains. PrLDs-containing proteins have been involved in different organisms' regulatory processes. Regions of moderate amyloid propensity within IDRs have been shown to assemble autonomously into amyloid fibrils. These sequences tend to be rich in polar amino acids and often escape from the detection of classical bioinformatics screenings that look for highly aggregation-prone hydrophobic sequence stretches. We defined them as cryptic amyloidogenic regions (CARs) and recently developed an integrated database that collects thousands of predicted CARs in IDRs. CARs seem to be evolutionary conserved among disordered regions because of their potential to stablish functional contacts with other biomolecules. Here we have focused on identifying and characterizing CARs in prion-like proteins (pCARs) from plants, a lineage that has been poorly studied in comparison with other prionomes. We confirmed the intrinsic amyloid potential for a selected pCAR from Arabidopsis thaliana and explored functional enrichments and compositional bias of pCARs in plant prion-like proteins.

Evolution of sequence traits of prion-like proteins linked to amyotrophic lateral sclerosis (ALS)

Prions are proteinaceous particles that can propagate an alternative conformation to further copies of the same protein. They have been described in mammals, fungi, bacteria and archaea. Furthermore, across diverse organisms from bacteria to eukaryotes, prion-like proteins that have similar sequence characters are evident. Such prion-like proteins have been linked to pathomechanisms of amyotrophic lateral sclerosis (ALS) in humans, in particular TDP43, FUS, TAF15, EWSR1 and hnRNPA2. Because of the desire to study human disease-linked proteins in model organisms, and to gain insights into the functionally important parts of these proteins and how they have changed across hundreds of millions of years of evolution, we analyzed how the sequence traits of these five proteins have evolved across eukaryotes, including plants and metazoa. We discover that the RNA-binding domain architecture of these proteins is deeply conserved since their emergence. Prion-like regions are also deeply and widely conserved since the origination of the protein families for FUS, TAF15 and EWSR1, and since the last common ancestor of metazoa for TDP43 and hnRNPA2. Prion-like composition is uncommon or weak in any plant orthologs observed, however in TDP43 many plant proteins have equivalent regions rich in other amino acids (namely glycine and tyrosine and/or serine) that may be linked to stress granule recruitment. Deeply conserved low-complexity domains are identified that likely have functional significance.

Landscape of biomolecular condensates in heat stress responses

High temperature is one of the abiotic stresses that plants face and acts as a major constraint on crop production and food security. Plants have evolved several mechanisms to overcome challenging environments and respond to internal and external stimuli. One significant mechanism is the formation of biomolecular condensates driven by liquid-liquid phase separation. Biomolecular condensates have received much attention in the past decade, especially with regard to how plants perceive temperature fluctuations and their involvement in stress response and tolerance. In this review, we compile and discuss examples of plant biomolecular condensates regarding their composition, localization, and functions triggered by exposure to heat. Bioinformatic tools can be exploited to predict heat-induced biomolecular condensates. As the field of biomolecular condensates has emerged in the study of plants, many intriguing questions have arisen that have yet to be solved. Increased knowledge of biomolecular condensates will help in securing crop production and overcoming limitations caused by heat stress.

In-Silico Analysis of pH-Dependent Liquid-Liquid Phase Separation in Intrinsically Disordered Proteins

Intrinsically disordered proteins (IDPs) are essential players in the assembly of biomolecular condensates during liquid–liquid phase separation (LLPS). Disordered regions (IDRs) are significantly exposed to the solvent and, therefore, highly influenced by fluctuations in the microenvironment. Extrinsic factors, such as pH, modify the solubility and disorder state of IDPs, which in turn may impact the formation of liquid condensates. However, little attention has been paid to how the solution pH influences LLPS, despite knowing that this process is context-dependent. Here, we have conducted a large-scale in-silico analysis of pH-dependent solubility and disorder in IDRs known to be involved in LLPS (LLPS-DRs). We found that LLPS-DRs present maximum solubility around physiological pH, where LLPS often occurs, and identified significant differences in solubility and disorder between proteins that can phase-separate by themselves or those that require a partner. We also analyzed the effect of mutations in the resulting solubility profiles of LLPS-DRs and discussed how, as a general trend, LLPS-DRs display physicochemical properties that permit their LLPS at physiologically relevant pHs.