Computational and statistical analyses of amino acid usage and physico-chemical properties of the twelve late embryogenesis abundant protein classes

Late Embryogenesis Abundant Proteins Contribute to the Resistance of Toxoplasma gondii Oocysts against Environmental Stresses

Toxoplasma gondii oocysts, which are shed in large quantities in the feces from infected felines, are very stable in the environment, resistant to most inactivation procedures, and highly infectious. The oocyst wall provides an important physical barrier for sporozoites contained inside oocysts, protecting them from many chemical and physical stressors, including most inactivation procedures. Furthermore, sporozoites can withstand large temperature changes, even freeze-thawing, as well as desiccation, high salinity, and other environmental insults; however, the genetic basis for this environmental resistance is unknown. Here, we show that a cluster of four genes encoding Late Embryogenesis Abundant (LEA)-related proteins are required to provide Toxoplasma sporozoites resistance to environmental stresses. Toxoplasma LEA-like genes (TgLEAs) exhibit the characteristic features of intrinsically disordered proteins, explaining some of their properties. Our in vitro biochemical experiments using recombinant TgLEA proteins show that they have cryoprotective effects on the oocyst-resident lactate dehydrogenase enzyme and that induced expression in E. coli of two of them leads to better survival after cold stress. Oocysts from a strain in which the four LEA genes were knocked out en bloc were significantly more susceptible to high salinity, freezing, and desiccation compared to wild-type oocysts. We discuss the evolutionary acquisition of LEA-like genes in Toxoplasma and other oocyst-producing apicomplexan parasites of the Sarcocystidae family and discuss how this has likely contributed to the ability of sporozoites within oocysts to survive outside the host for extended periods. Collectively, our data provide a first molecular detailed view on a mechanism that contributes to the remarkable resilience of oocysts against environmental stresses. IMPORTANCE Toxoplasma gondii oocysts are highly infectious and may survive in the environment for years. Their resistance against disinfectants and irradiation has been attributed to the oocyst and sporocyst walls by acting as physical and permeability barriers. However, the genetic basis for their resistance against stressors like changes in temperature, salinity, or humidity, is unknown. We show that a cluster of four genes encoding Toxoplasma Late Embryogenesis Abundant (TgLEA)-related proteins are important for this resistance to environmental stresses. TgLEAs have features of intrinsically disordered proteins, explaining some of their properties. Recombinant TgLEA proteins show cryoprotective effects on the parasite's lactate dehydrogenase, an abundant enzyme in oocysts, and expression in E. coli of two TgLEAs has a beneficial effect on growth after cold stress. Moreover, oocysts from a strain lacking all four TgLEA genes were more susceptible to high salinity, freezing, and desiccation compared to wild-type oocysts, highlighting the importance of the four TgLEAs for oocyst resilience.

Genome-wide identification and analysis of LEA_2 gene family in alfalfa (Medicago sativa L.) under aluminum stress

Late embryonic development abundant proteins (LEAs) are a large family of proteins commonly existing in plants. LEA_2 is the largest subfamily in the LEA, it plays an important role in plant resistance to abiotic stress. In order to explore the characteristics of LEA_2 gene family members in alfalfa (Medicago sativa L.), 155 members of LEA_2 (MsLEA_2) family were identified from alfalfa genome. Bioinformatics analysis was conducted from the aspects of phylogenetic relationship, chromosome distribution, chromosome colinearity, physical and chemical properties, motif composition, exon-intron structure, cis-element and so on. Expression profiles of MsLEA_2 gene were obtained based on Real-time fluorescent quantitative PCR (qRT-PCR) analysis and previous RNA-seq data under aluminum (Al) stress. Bioinformatics results were shown that the MsLEA_2 genes are distributed on all 32 chromosomes. Among them, 85 genes were present in the gene clusters, accounting for 54.83%, and chromosome Chr7.3 carries the largest number of MsLEA_2 (19 LEA_2 genes on Chr7.3). Chr7.3 has a unique structure of MsLEA_2 distribution, which reveals a possible special role of Chr7.3 in ensuring the function of MsLEA_2. Transcriptional structure analysis revealed that the number of exons in each gene varies from 1 to 3, and introns varies from 0 to 2. Cis-element analysis identified that the promoter region of MsLEA_2 is rich in ABRE, MBS, LTR, and MeJARE, indicating MsLEA_2 has stress resistance potential under abiotic stress. RNA-seq data and qRT-PCR analyses showed that most of the MsLEA_2 members were up-regulated when alfalfa exposed to Al stress. This study revealed that phylogenetic relationship and possible function of LEA_ 2 gene in alfalfa, which were helpful for the functional analysis of LEA_ 2 proteins in the future and provided a new theoretical basis for improving Al tolerance of alfalfa.

LEAfing through literature: late embryogenesis abundant proteins coming of age-achievements and perspectives

To deal with increasingly severe periods of dehydration related to global climate change, it becomes increasingly important to understand the complex strategies many organisms have developed to cope with dehydration and desiccation. While it is undisputed that late embryogenesis abundant (LEA) proteins play a key role in the tolerance of plants and many anhydrobiotic organisms to water limitation, the molecular mechanisms are not well understood. In this review, we summarize current knowledge of the physiological roles of LEA proteins and discuss their potential molecular functions. As these are ultimately linked to conformational changes in the presence of binding partners, post-translational modifications, or water deprivation, we provide a detailed summary of current knowledge on the structure-function relationship of LEA proteins, including their disordered state in solution, coil to helix transitions, self-assembly, and their recently discovered ability to undergo liquid-liquid phase separation. We point out the promising potential of LEA proteins in biotechnological and agronomic applications, and summarize recent advances. We identify the most relevant open questions and discuss major challenges in establishing a solid understanding of how these intriguing molecules accomplish their tasks as cellular sentinels at the limits of surviving water scarcity.

In silico functional annotation of hypothetical proteins from the Bacillus paralicheniformis strain Bac84 reveals proteins with biotechnological potentials and adaptational functions to extreme environments

Members of the Bacillus genus are industrial cell factories due to their capacity to secrete significant quantities of biomolecules with industrial applications. The Bacillus paralicheniformis strain Bac84 was isolated from the Red Sea and it shares a close evolutionary relationship with Bacillus licheniformis. However, a significant number of proteins in its genome are annotated as functionally uncharacterized hypothetical proteins. Investigating these proteins' functions may help us better understand how bacteria survive extreme environmental conditions and to find novel targets for biotechnological applications. Therefore, the purpose of our research was to functionally annotate the hypothetical proteins from the genome of B. paralicheniformis strain Bac84. We employed a structured in-silico approach incorporating numerous bioinformatics tools and databases for functional annotation, physicochemical characterization, subcellular localization, protein-protein interactions, and three-dimensional structure determination. Sequences of 414 hypothetical proteins were evaluated and we were able to successfully attribute a function to 37 hypothetical proteins. Moreover, we performed receiver operating characteristic analysis to assess the performance of various tools used in this present study. We identified 12 proteins having significant adaptational roles to unfavorable environments such as sporulation, formation of biofilm, motility, regulation of transcription, etc. Additionally, 8 proteins were predicted with biotechnological potentials such as coenzyme A biosynthesis, phenylalanine biosynthesis, rare-sugars biosynthesis, antibiotic biosynthesis, bioremediation, and others. Evaluation of the performance of the tools showed an accuracy of 98% which represented the rationality of the tools used. This work shows that this annotation strategy will make the functional characterization of unknown proteins easier and can find the target for further investigation. The knowledge of these hypothetical proteins' potential functions aids B. paralicheniformis strain Bac84 in effectively creating a new biotechnological target. In addition, the results may also facilitate a better understanding of the survival mechanisms in harsh environmental conditions.

The acyclotide ribe 31 from Rinorea bengalensis has selective cytotoxicity and potent insecticidal properties in Drosophila

Cyclotides and acyclic versions of cyclotides (acyclotides) are peptides involved in plant defense. These peptides contain a cystine knot motif formed by three interlocked disulfide bonds, with the main difference between the two classes being the presence or absence of a cyclic backbone, respectively. The insecticidal activity of cyclotides is well documented, but no study to date explores the insecticidal activity of acyclotides. Here, we present the first in vivo evaluation of the insecticidal activity of acyclotides from Rinorea bengalensis on the vinegar fly Drosophila melanogaster. Of a group of structurally comparable acyclotides, ribe 31 showed the most potent toxicity when fed to D. melanogaster. We screened a range of acyclotides and cyclotides and found their toxicity toward human red blood cells was substantially lower than toward insect cells, highlighting their selectivity and potential for use as bioinsecticides. Our confocal microscopy experiments indicated their cytotoxicity is likely mediated via membrane disruption. Furthermore, our surface plasmon resonance studies suggested ribe 31 preferentially binds to membranes containing phospholipids with phosphatidyl-ethanolamine headgroups. Despite having an acyclic backbone, we determined the three-dimensional NMR solution structure of ribe 31 is similar to that of cyclotides. In summary, our results suggest that, with further optimization, ribe 31 could have applications as an insecticide due to its potent in vivo activity against D. melanogaster. More broadly, this work advances the field by demonstrating that acyclotides are more common than previously thought, have potent insecticidal activity, and have the advantage of potentially being more easily manufactured than cyclotides.

In-silico design of an immunoinformatics based multi-epitope vaccine against Leishmania donovani

BACKGROUND

Visceral Leishmaniasis (VL) is a fatal vector-borne parasitic disorder occurring mainly in tropical and subtropical regions. VL falls under the category of neglected tropical diseases with growing drug resistance and lacking a licensed vaccine. Conventional vaccine synthesis techniques are often very laborious and challenging. With the advancement of bioinformatics and its application in immunology, it is now more convenient to design multi-epitope vaccines comprising predicted immuno-dominant epitopes of multiple antigenic proteins. We have chosen four antigenic proteins of Leishmania donovani and identified their T-cell and B-cell epitopes, utilizing those for in-silico chimeric vaccine designing. The various physicochemical characteristics of the vaccine have been explored and the tertiary structure of the chimeric construct is predicted to perform docking studies and molecular dynamics simulations.

RESULTS

The vaccine construct is generated by joining the epitopes with specific linkers. The predicted tertiary structure of the vaccine has been found to be valid and docking studies reveal the construct shows a high affinity towards the TLR-4 receptor. Population coverage analysis shows the vaccine can be effective on the majority of the world population. In-silico immune simulation studies confirms the vaccine to raise a pro-inflammatory response with the proliferation of activated T and B cells. In-silico codon optimization and cloning of the vaccine nucleic acid sequence have also been achieved in the pET28a vector.

CONCLUSION

The above bioinformatics data support that the construct may act as a potential vaccine. Further wet lab synthesis of the vaccine and in vivo works has to be undertaken in animal model to confirm vaccine potency.

Cloning and function analysis of a Saussurea involucrata LEA4 gene

Late embryogenesis abundant proteins (LEA) help adapt to adverse low-temperature environments. The Saussurea involucrate SiLEA4, which encodes a membrane protein, was significantly up-regulated in response to low temperature stress. Escherichia coli expressing SiLEA4 showed enhanced low-temperature tolerance, as evident from the significantly higher survival numbers and growth rates at low temperatures. Moreover, tomato strains expressing SiLEA4 had significantly greater freezing resistance, due to a significant increase in the antioxidase activities and proline content. Furthermore, they had higher yields due to higher water utilization and photosynthetic efficiency under the same water and fertilizer conditions. Thus, expressing SiLEA4 has multiple advantages: (1) mitigating chilling injury, (2) increasing yields, and (3) water-saving, which also indicates the great potential of the SiLEA4 for breeding applications.

Late Embryogenesis Abundant (LEA)5 Regulates Translation in Mitochondria and Chloroplasts to Enhance Growth and Stress Tolerance

The late embryogenesis abundant (LEA)5 protein is predominantly expressed in Arabidopsis leaves in the dark, the levels of LEA5 transcripts decreasing rapidly upon illumination. LEA5 is important in plant responses to environmental stresses but the mechanisms involved have not been elucidated. We therefore explored LEA5 functions in Arabidopsis mutants (lea5) and transgenic Arabidopsis plants constitutively expressing LEA5 (OEX 2-5), as well as in transgenic barley lines expressing the Arabidopsis LEA5 gene. The OEX 2-5 plants grew better than controls and lea5 mutants in the presence of the prooxidants methyl viologen and menadione. Confocal microscopy of Arabidopsis mesophyll protoplasts expressing a LEA5-YFP fusion protein demonstrated that LEA5 could be localized to chloroplasts as well as mitochondria in Arabidopsis protoplasts. Tandem affinity purification (TAP) analysis revealed LEA5 interacts with the chloroplast DEAD-box ATP-dependent RNA helicase 22 (RH22) in Arabidopsis cells. Split YFP analysis confirmed the interaction between RH22 and LEA5 in chloroplasts. The abundance of translated protein products in chloroplasts was decreased in transgenic Arabidopsis plants and increased in lea5 knockout mutants. Conversely, the abundance of translated mitochondrial protein products was increased in OEX 2-5 plants and decreased in lea5 mutants. Mitochondrial electron transport rates were higher in the OEX 2-5 plants than the wild type. The transformed barley lines expressing the Arabidopsis LEA5 had increased seed yields, but they showed a greater drought-induced inhibition of photosynthesis than controls. Taken together, these data demonstrate that LEA5 regulates organellar translation, in order to enhance respiration relative to photosynthesis in response to stress.

Questing functions and structures of hypothetical proteins from Campylobacter jejuni: a computer-aided approach

Campylobacter jejuni (C. jejuni) is considered to be one of the most frequent causes of bacterial gastroenteritis globally, especially in young children. The genome of C. jejuni contains many proteins with unknown functions termed as hypothetical proteins (HPs). These proteins might have essential biological role to show the full spectrum of this bacterium. Hence, our study aimed to determine the functions of HPs, pertaining to the genome of C. jejuni. An in-silico work flow integrating various tools were performed for functional assignment, three-dimensional structure determination, domain architecture predictors, subcellular localization, physicochemical characterization, and protein-protein interactions (PPIs). Sequences of 267 HPs of C. jejuni were analyzed and successfully attributed the function of 49 HPs with higher confidence. Here, we found proteins with enzymatic activity, transporters, binding and regulatory proteins as well as proteins with biotechnological interest. Assessment of the performance of various tools used in this analysis revealed an accuracy of 95% using receiver operating characteristic (ROC) curve analysis. Functional and structural predictions and the results from ROC analyses provided the validity of in-silico tools used in the present study. The approach used for this analysis leads us to assign the function of unknown proteins and relate them with the functions that have already been described in previous literature.

Structural and Functional Characterization of the ABA-Water Deficit Stress Domain from Wheat and Barley: An Intrinsically Disordered Domain behind the Versatile Functions of the Plant Abscissic Acid, Stress and Ripening Protein Family

The ASR protein family has been discovered thirty years ago in many plant species and is involved in the tolerance of various abiotic stresses such as dehydration, salinity and heat. Despite its importance, nothing is known about the conserved ABA-Water Deficit Stress Domain (ABA-WDS) of the ASR gene family. In this study, we characterized two ABA-WDS domains, isolated from durum wheat (TtABA-WDS) and barley (HvABA-WDS). Bioinformatics analysis shows that they are both consistently predicted to be intrinsically disordered. Hydrodynamic and circular dichroism analysis indicate that both domains are largely disordered but belong to different structural classes, with HvABA-WDS and TtABA-WDS adopting a PreMolten Globule-like (PMG-like) and a Random Coil-like (RC-like) conformation, respectively. In the presence of the secondary structure stabilizer trifluoroethanol (TFE) or of increasing glycerol concentrations, which mimics dehydration, the two domains acquire an α-helical structure. Interestingly, both domains are able to prevent heat- and dehydration-induced inactivation of the enzyme lactate dehydrogenase (LDH). Furthermore, heterologous expression of TtABA-WDS and HvABA-WDS in the yeast Saccharomyces cerevisiae improves its tolerance to salt, heat and cold stresses. Taken together our results converge to show that the ABA-WDS domain is an intrinsically disordered functional domain whose conformational plasticity could be instrumental to support the versatile functions attributed to the ASR family, including its role in abiotic stress tolerance. Finally, and after validation in the plant system, this domain could be used to improve crop tolerance to abiotic stresses.

The in vitro structure and functions of the disordered late embryogenesis abundant three proteins

Late embryogenesis abundant (LEA) proteins are produced during seed embryogenesis and in vegetative tissue in response to various abiotic stressors. A correlation has been established between LEA expression and stress tolerance, yet their precise biochemical mechanism remains elusive. LEA proteins are very rich in hydrophilic amino acids, and they have been found to be intrinsically disordered proteins (IDPs) in vitro. Here, we perform biochemical and structural analyses of the four LEA3 proteins from Arabidopsis thaliana (AtLEA3). We show that the LEA3 proteins are disordered in solution but have regions with propensity for order. All LEA3 proteins were effective cryoprotectants of LDH in the freeze/thaw assays, while only one member, AtLEA3-4, was shown to bind Cu²⁺ and Fe³⁺ ions with micromolar affinity. As well, only AtLEA3-4 showed binding and a gain in α-helicity in the presence of the membrane mimic dodecylphosphocholine (DPC). We explored this interaction in greater detail using ¹⁵ N-heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance, and demonstrate that two sets of conserved motifs present in AtLEA3-4 are involved in the interaction with the DPC micelles, which themselves gain α-helical structure.

Identification of novel seed longevity genes related to oxidative stress and seed coat by genome-wide association studies and reverse genetics

Seed longevity is a polygenic trait of relevance for agriculture and for understanding the effect of environment on the ageing of biological systems. In order to identify novel longevity genes, we have phenotyped the natural variation of 270 ecotypes of the model plant, Arabidopsis thaliana, for natural ageing and for three accelerated ageing methods. Genome-wide analysis, using publicly available single-nucleotide polymorphisms (SNPs) data sets, identified multiple genomic regions associated with variation in seed longevity. Reverse genetics of 20 candidate genes in Columbia ecotype resulted in seven genes positive for seed longevity (PSAD1, SSLEA, SSTPR, DHAR1, CYP86A8, MYB47 and SPCH) and five negative ones (RBOHD, RBOHE, RBOHF, KNAT7 and SEP3). In this uniform genetic background, natural and accelerated ageing methods provided similar results for seed-longevity in knock-out mutants. The NADPH oxidases (RBOHs), the dehydroascorbate reductase (DHAR1) and the photosystem I subunit (PSAD1) highlight the important role of oxidative stress on seed ageing. The cytochrome P-450 hydroxylase, CYP86A8, and the transcription factors, MYB47, KNAT7 and SEP3, support the protecting role of the seed coat during seed ageing.

Conserved sequence motifs in the abiotic stress response protein late embryogenesis abundant 3

LEA3 proteins, a family of abiotic stress proteins, are defined by the presence of a tryptophan-containing motif, which we name the W-motif. We use Pfam LEA3 sequences to search the Phytozome database to create a W-motif definition and a LEA3 sequence dataset. A comprehensive analysis of these sequences revealed four N-terminal motifs, as well as two previously undiscovered C-terminal motifs that contain conserved acidic and hydrophobic residues. The general architecture of the LEA3 sequences consisted of an N-terminal motif with a potential mitochondrial transport signal and the twin-arginine motif cut-site, followed by a W-motif and often a C-terminal motif. Analysis of species distribution of the motifs showed that one architecture was found exclusively in Commelinids, while two were distributed fairly evenly over all species. The physiochemical properties of the different architectures showed clustering in a relatively narrow range compared to the previously studied dehydrins. The evolutionary analysis revealed that the different sequences grouped into clades based on architecture, and that there appear to be at least two distinct groups of LEA3 proteins based on their architectures and physiochemical properties. The presence of LEA3 proteins in non-vascular plants but their absence in algae suggests that LEA3 may have arisen in the evolution of land plants.

Characteristics, dynamics and mechanisms of actions of some major stress-induced biomacromolecules; addressing Artemia as an excellent biological model

Stress tolerance is one of the most prominent and interesting topics in biology since many macro- and micro-adaptations have evolved in resistant organisms that are worth studying. When it comes to confronting various environmental stressors, the extremophile Artemia is unrivaled in the animal kingdom. In the present review, the evolved molecular and cellular basis of stress tolerance in resistant biological systems are described, focusing on Artemia cyst as an excellent biological model. The main purpose of the review is to discuss how the structure and physicochemical characteristics of protective factors such as late embryogenesis abundant proteins (LEAPs), small heat shock proteins (sHSPs) and trehalose are related to their functions and by which mechanisms, they exert their functions. In addition, some metabolic depressors in Artemia encysted embryos are also mentioned, indirectly playing important roles in stress tolerance. Importantly, a great deal of attention is given to the LEAPs, exhibiting distinctive folding behaviors and mechanisms of actions. For instance, molecular shield function, chaperone-like activity, moonlighting property, sponging and snorkeling capabilities of the LEAPs are delineated here. Moreover, the molecular interplay between some of these factors is mentioned, leading to their synergistic effects. Interestingly, Artemia life cycle adapts to environmental conditions. Diapause is the defense mode of this life cycle, safeguarding Artemia encysted embryos against various environmental stressors. Communicated by Ramaswamy H. Sarma.

Common Functions of Disordered Proteins across Evolutionary Distant Organisms

Intrinsically disordered proteins and regions typically lack a well-defined structure and thus fall outside the scope of the classic sequence–structure–function relationship. Hence, classic sequence- or structure-based bioinformatic approaches are often not well suited to identify homology or predict the function of unknown intrinsically disordered proteins. Here, we give selected examples of intrinsic disorder in plant proteins and present how protein function is shared, altered or distinct in evolutionary distant organisms. Furthermore, we explore how examining the specific role of disorder across different phyla can provide a better understanding of the common features that protein disorder contributes to the respective biological mechanism.

Structural properties and cellular expression of AfrLEA6, a group 6 late embryogenesis abundant protein from embryos of Artemia franciscana

Late embryogenesis abundant (LEA) proteins are intrinsically disordered proteins (IDPs) commonly found in anhydrobiotic organisms and are frequently correlated with desiccation tolerance. Herein we report new findings on AfrLEA6, a novel group 6 LEA protein from embryos of Artemia franciscana. Assessment of secondary structure in aqueous and dried states with circular dichroism (CD) reveals 89% random coil in the aqueous state, thus supporting classification of AfrLEA6 as an IDP. Removal of water from the protein by drying or exposure to trifluoroethanol (a chemical de-solvating agent) promotes a large gain in secondary structure of AfrLEA6, predominated by α-helix and exhibiting minimal β-sheet structure. We evaluated the impact of physiological concentrations (up to 400 mM) of the disaccharide trehalose on the folding of LEA proteins in solution. CD spectra for AfrLEA2, AfrLEA3m, and AfrLEA6 are unaffected by this organic solute noted for its ability to drive protein folding. AfrLEA6 exhibits its highest concentration in vivo during embryonic diapause, drops acutely at diapause termination, and then declines during development to undetectable values at the larval stage. Maximum cellular titer of AfrLEA6 was 10-fold lower than for AfrLEA2 or AfrLEA3, both group 3 LEA proteins. Acute termination of diapause with H2O2 (a far more effective terminator than desiccation in this Great Salt Lake, UT, population) fostered a rapid 38% decrease in AfrLEA6 content of embryos. While the ultimate mechanism of diapause termination is unknown, disruption of key macromolecules could initiate physiological signaling events necessary for resumption of development and metabolism.

Preferential adsorption to air-water interfaces: a novel cryoprotective mechanism for LEA proteins

Late embryogenesis abundant (LEA) proteins comprise a diverse family whose members play a key role in abiotic stress tolerance. As intrinsically disordered proteins, LEA proteins are highly hydrophilic and inherently stress tolerant. They have been shown to stabilise multiple client proteins under a variety of stresses, but current hypotheses do not fully explain how such broad range stabilisation is achieved. Here, using neutron reflection and surface tension experiments, we examine in detail the mechanism by which model LEA proteins, AavLEA1 and ERD10, protect the enzyme citrate synthase (CS) from aggregation during freeze–thaw. We find that a major contributing factor to CS aggregation is the formation of air bubbles during the freeze–thaw process. This greatly increases the air–water interfacial area, which is known to be detrimental to folded protein stability. Both model LEA proteins preferentially adsorb to this interface and compete with CS, thereby reducing surface-induced aggregation. This novel surface activity provides a general mechanism by which diverse members of the LEA protein family might function to provide aggregation protection that is not specific to the client protein.

Structural properties and enzyme stabilization function of the intrinsically disordered LEA_4 protein TdLEA3 from wheat

Late Embryogenesis Abundant (LEA) proteins are mostly predicted to be intrinsically disordered proteins (IDPs) that are induced under conditions of cellular dehydration. Their functions, however, are largely unexplored and also their structure and interactions with potential target molecules have only recently been investigated in a small number of proteins. Here, we have characterized the wheat LEA protein TdLEA3, which has sequence homology with the group of LEA_4 proteins that are characterized by the 11-mer repeat motif TAQAAKEKAXE. TdLEA3 has five repeats of this imperfectly conserved 11-mer amino acid motif. To investigate the structure of the protein, we used circular dichroism (CD) and Fourier-transform infrared (FTIR) spectroscopy. The data show that TdLEA3 was largely disordered under fully hydrated conditions and acquired α-helical structure upon drying and in the presence of trifluoroethanol (TFE). Moreover, the addition of increasing glycerol concentrations to the protein solution induced a progressive gain in α-helix content. Activity assays indicated that TdLEA3 was able to prevent the inactivation of lactate dehydrogenase (LDH) under heat, dehydration-rehydration and freeze-thaw treatments. In addition, TdLEA3 reduced aggregate formation in the enzyme during these treatments.

Dehydration-induced proteomic landscape of mitochondria in chickpea reveals large-scale coordination of key biological processes

Mitochondria play crucial roles in regulating multiple biological processes particularly electron transfer and energy metabolism in eukaryotic cells. Exposure to water-deficit or dehydration may affect mitochondrial function, and dehydration response may dictate cell fate decisions. iTRAQ-based quantitative proteome of a winter legume, chickpea, demonstrated the central metabolic alterations in mitochondria, presumably involved in dehydration adaptation. Three-week-old chickpea seedlings were subjected to progressive dehydration and the magnitude of dehydration-induced compensatory physiological responses was monitored in terms of physicochemical characteristics and mitochondrial architecture. The proteomics analysis led to the identification of 40 dehydration-responsive proteins whose expressions were significantly modulated by dehydration. The differentially expressed proteins were implicated in different metabolic processes, with obvious functional tendencies toward purine-thiamine metabolic network, pathways of carbon fixation and oxidative phosphorylation. The linearity of dehydration-induced proteome alteration was examined with transcript abundance of randomly selected candidates under multivariate stress conditions. The differentially regulated proteins were validated through sequence analysis. An extensive sequence based localization prediction revealed >62.5% proteins to be mitochondrial resident by, at least, one prediction algorithm. The results altogether provide intriguing insights into the dehydration-responsive metabolic pathways and useful clues to identify crucial proteins linked to stress tolerance. BIOLOGICAL SIGNIFICANCE: Investigation on plant mitochondrial proteome is of significance because it would allow a better understanding of mitochondrial function in plant adaptation to stress. Mitochondria are the unique organelles, which play a crucial role in energy metabolism and cellular homeostasis, particularly when exposed to stress conditions. Chickpea is one of the cultivated winter legumes, which enriches soil nitrogen and has very low water footprint and thus contributes to fortification of sustainable agriculture. We therefore examined the dehydration-responsive mitochondrial proteome landscape of chickpea and queried whether molecular interplay of mitochondrial proteins modulate dehydration tolerance. A total of 40 dehydration-induced mitochondrial proteins were identified, predicted to be involved in key metabolic processes. Our future efforts would focus on understanding both posttranslational modification and processing for comprehensive characterization of mitochondrial protein function. This approach will facilitate mining of more biomarkers linked to the tolerance trait and contribute to crop adaptation to climate change.

Analysis of pcC13-62 promoters predicts a link between cis-element variations and desiccation tolerance in Linderniaceae

Reproductive structures of plants (e.g. seeds) and vegetative tissues of resurrection plants can tolerate desiccation. Many genes encoding desiccation-related proteins (DRPs) have been identified in the resurrection plant Craterostigma plantagineum, but the function of these genes remains mainly hypothetical. Here, the importance of the DRP gene pcC13-62 for desiccation tolerance is evaluated by analysing its expression in C. plantagineum and in the closely related desiccation-tolerant species Lindernia brevidens and the desiccation-sensitive species Lindernia subracemosa. Quantitative analysis revealed that pcC13-62 transcripts accumulate at a much lower level in desiccation-sensitive species than in desiccation-tolerant species. The study of pcC13-62 promoters from these species demonstrated a correlation between promoter activity and gene expression levels, suggesting transcriptional regulation of gene expression. Comparison of promoter sequences identified a dehydration-responsive element motif in the promoters of tolerant species that is required for dehydration-induced β-glucuronidase (GUS) accumulation. We hypothesize that variations in the regulatory sequences of the pcC13-62 gene occurred to establish pcC13-62 expression in vegetative tissues, which might be required for desiccation tolerance. The pcC13-62 promoters could also be activated by salt stress in Arabidopsis thaliana plants stably transformed with promoter::GUS constructs.

Structural disorder and induced folding within two cereal, ABA stress and ripening (ASR) proteins

Abscisic acid (ABA), stress and ripening (ASR) proteins are plant-specific proteins involved in plant response to multiple abiotic stresses. We previously isolated the ASR genes and cDNAs from durum wheat (TtASR1) and barley (HvASR1). Here, we show that HvASR1 and TtASR1 are consistently predicted to be disordered and further confirm this experimentally. Addition of glycerol, which mimics dehydration, triggers a gain of structure in both proteins. Limited proteolysis showed that they are highly sensitive to protease degradation. Addition of 2,2,2-trifluoroethanol (TFE) however, results in a decreased susceptibility to proteolysis that is paralleled by a gain of structure. Mass spectrometry analyses (MS) led to the identification of a protein fragment resistant to proteolysis. Addition of zinc also induces a gain of structure and Hydrogen/Deuterium eXchange-Mass Spectrometry (HDX-MS) allowed identification of the region involved in the disorder-to-order transition. This study is the first reported experimental characterization of HvASR1 and TtASR1 proteins, and paves the way for future studies aimed at unveiling the functional impact of the structural transitions that these proteins undergo in the presence of zinc and at achieving atomic-resolution conformational ensemble description of these two plant intrinsically disordered proteins (IDPs).

Potential functions of LEA proteins from the brine shrimp Artemia franciscana - anhydrobiosis meets bioinformatics

Late embryogenesis abundant (LEA) proteins are a large group of anhydrobiosis-associated intrinsically disordered proteins, which are commonly found in plants and some animals. The brine shrimp Artemia franciscana is the only known animal that expresses LEA proteins from three, and not only one, different groups in its anhydrobiotic life stage. The reason for the higher complexity in the A. franciscana LEA proteome (LEAome), compared with other anhydrobiotic animals, remains mostly unknown. To address this issue, we have employed a suite of bioinformatics tools to evaluate the disorder status of the Artemia LEAome and to analyze the roles of intrinsic disorder in functioning of brine shrimp LEA proteins. We show here that A. franciscana LEA proteins from different groups are more similar to each other than one originally expected, while functional differences among members of group three are possibly larger than commonly anticipated. Our data show that although these proteins are characterized by a large variety of forms and possible functions, as a general strategy, A. franciscana utilizes glassy matrix forming LEAs concurrently with proteins that more readily interact with binding partners. It is likely that the function(s) of both types, the matrix-forming and partner-binding LEA proteins, are regulated by changing water availability during desiccation.

Involvement of C-Terminal Histidines in Soybean PM1 Protein Oligomerization and Cu2+ Binding

Late embryogenesis abundant (LEA) proteins are widely distributed among plant species, where they contribute to abiotic stress tolerance. LEA proteins can be classified into seven groups according to conserved sequence motifs. The PM1 protein from soybean, which belongs to the Pfam LEA_1 group, has been shown previously to be at least partially natively unfolded, to bind metal ions and potentially to stabilize proteins and membranes. Here, we investigated the role of the PM1 C-terminal domain and in particular the multiple histidine residues in this half of the protein. We constructed recombinant plasmids expressing full-length PM1 and two truncated forms, PM1-N and PM1-C, which represent the N- and C-terminal halves of the protein, respectively. Immunoblotting and cross-linking experiments showed that full-length PM1 forms oligomers and high molecular weight (HMW) complexes in vitro and in vivo, while PM1-C, but not PM1-N, also formed oligomers and HMW complexes in vitro. When the histidine residues in PM1 and PM1-C were chemically modified, oligomerization was abolished, suggesting that histidines play a key role in this process. Furthermore, we demonstrated that high Cu2+ concentrations promote oligomerization and induce PM1 and PM1-C to form HMW complexes. Therefore, we speculate that PM1 proteins not only maintain ion homeostasis in the cytoplasm, but also potentially stabilize and protect other proteins during abiotic stress by forming a large, oligomeric molecular shield around biological targets.

Peptide-protein interactions within human hair keratins

We selected 1235 decapeptides from human hair proteins encoded by human genes of keratins and keratin associated proteins. The peptides were linked to glass arrays and screened for their affinity towards a solution of human hair extracted keratin fraction. Based on the physicochemical properties of the peptides, ten variables were studied: content of different types of amino acid side chains (cysteine, hydrophobic, polar, basic, acidic, aromatic rings, amide, alcohol side chains), isoelectric point, and net charge. We found differences statistically significant on the binding affinity of peptides based on their content of cysteine, hydrophobic and polar amino acids, mainly containing alcohols. These results point to the formation of hydrophobic interactions and disulfide bonds between small peptides and human hair keratins as the main driving forces for the interaction of possible cosmetic peptides, namely designed to strength human hair. As so, our results enlighten the nature of the interaction of keratin based materials with human hair, which are claimed to enhance hair fiber strength, and enable a more directed and sustained hair care peptide design.

SmLEA2, a gene for late embryogenesis abundant protein isolated from Salvia miltiorrhiza, confers tolerance to drought and salt stress in Escherichia coli and S. miltiorrhiza

Abiotic stresses, such as drought and high salinity, are major factors that limit plant growth and productivity. Late embryogenesis abundant (LEA) proteins are members of a diverse, multigene family closely associated with tolerance to abiotic stresses in numerous organisms. We examined the function of SmLEA2, previously isolated from Salvia miltiorrhiza, in defense responses to drought and high salinity. Phylogenetic analysis indicated that SmLEA2 belongs to the LEA_2 subfamily. Its overexpression in Escherichia coli improved growth performance when compared with the control under salt and drought stresses. We further characterized its roles in S. miltiorrhiza through overexpression and RNAi-mediated silencing. In response to drought and salinity treatments, transgenic plants overexpressing SmLEA2 exhibited significantly increased superoxide dismutase activity, reduced levels of lipid peroxidation, and more vigorous growth than empty-vector control plants did. However, transgenic lines in which expression was suppressed showed the opposite results. Our data demonstrate that SmLEA2 plays an important role in the abiotic stress response and its overexpression in transgenic S. miltiorrhiza improves tolerance to excess salt and drought conditions.

Insights on Structure and Function of a Late Embryogenesis Abundant Protein from Amaranthus cruentus: An Intrinsically Disordered Protein Involved in Protection against Desiccation, Oxidant Conditions, and Osmotic Stress

Late embryogenesis abundant (LEA) proteins are part of a large protein family that protect other proteins from aggregation due to desiccation or osmotic stresses. Recently, the Amaranthus cruentus seed proteome was characterized by 2D-PAGE and one highly accumulated protein spot was identified as a LEA protein and was named AcLEA. In this work, AcLEA cDNA was cloned into an expression vector and the recombinant protein was purified and characterized. AcLEA encodes a 172 amino acid polypeptide with a predicted molecular mass of 18.34 kDa and estimated pI of 8.58. Phylogenetic analysis revealed that AcLEA is evolutionarily close to the LEA3 group. Structural characteristics were revealed by nuclear magnetic resonance and circular dichroism methods. We have shown that recombinant AcLEA is an intrinsically disordered protein in solution even at high salinity and osmotic pressures, but it has a strong tendency to take a secondary structure, mainly folded as α-helix, when an inductive additive is present. Recombinant AcLEA function was evaluated using Escherichia coli as in vivo model showing the important protection role against desiccation, oxidant conditions, and osmotic stress. AcLEA recombinant protein was localized in cytoplasm of Nicotiana benthamiana protoplasts and orthologs were detected in seeds of wild and domesticated amaranth species. Interestingly AcLEA was detected in leaves, stems, and roots but only in plants subjected to salt stress. This fact could indicate the important role of AcLEA protection during plant stress in all amaranth species studied.

Characterization of OsLEA1a and its inhibitory effect on the resistance of E. coli to diverse abiotic stresses

OsLEA1a is a late embryogenesis abundant (LEA) protein gene from Oryza sativa L, which contains an open reading frame of 282-bp that encodes a putative polypeptide of 93 amino acids. OsLEA1a protein contains abundant of Lys, Ala, Glu, Asp, Gly, Arg and Leu, but depleted in Cys, His, Phe, Trp and Tyr residues; and is strongly hydrophilic. OsLEA1a includes six helical domains and a β-sheet domain. Real-time PCR analysis showed that OsLEA1a was expressed in roots, leaves and panicles of rice, with no or only a few transcripts in stem tissues, and remained at a relatively higher level in leaves during the tillering period, the heading period, the filling period and the full ripe period. To make sense of OsLEA1a functions, TrxA-OsLEA1a fusion protein expression vector and OsLEA1a protein expression vector were transformed into Escherichia coli DL21 (DE3), respectively. The accumulation of the TrxA-OsLEA1a fusion protein or OsLEA1a protein interfered with the resistance of E. coli to high salinity, metal ions, hyperosmotic, oxidation, heat and freeze-thaw stresses. The purified TrxA-OsLEA1a fusion protein reduced stabilization of LDH and increased damage of diverse abiotic stresses to LDH. The findings suggested that the OsLEA1a may confor antibacterial activity under abiotic stresses.

Group 3 LEA protein model peptides protect enzymes against desiccation stress

We tested whether model peptides for group 3 late embryogenesis abundant (G3LEA) proteins, which we developed previously, are capable of maintaining the catalytic activities of enzymes dried in their presence. Three different peptides were compared: 1) PvLEA-22, which consists of two tandem repeats of the 11-mer motif found in G3LEA proteins from an African sleeping chironomid; 2) PvLEA-44, which is made of four tandem repeats of the same 11-mer motif; and 3) a peptide whose amino acid composition is the same as that of PvLEA-22, but whose sequence is scrambled. We selected two enzymes, lactate dehydrogenase (LDH) and β-d-galactosidase (BDG), as targets because they have different isoelectric point (pI) values, in the alkaline and acidic range, respectively. While these enzymes were almost inactivated when dried alone, their catalytic activity was preserved at ≥70% of native levels in the presence of any of the above three peptides. This degree of protection is comparable to that conferred by several full-length G3LEA proteins, as reported previously for LDH. Interestingly, the protective activity of the peptides was enhanced slightly when they were mixed with trehalose, especially when the molar content of the peptides was low. On the basis of these results, the G3LEA model peptides show promise as protectants for the dry preservation of enzymes/proteins with a wide range of pI values.

Stress tolerance during diapause and quiescence of the brine shrimp, Artemia

Oviparously developing embryos of the brine shrimp, Artemia, arrest at gastrulation and are released from females as cysts before entering diapause, a state of dormancy and stress tolerance. Diapause is terminated by an external signal, and growth resumes if conditions are permissible. However, if circumstances are unfavorable, cysts enter quiescence, a dormant stage that continues as long as adverse conditions persist. Artemia embryos in diapause and quiescence are remarkably resistant to environmental and physiological stressors, withstanding desiccation, cold, heat, oxidation, ultraviolet radiation, and years of anoxia at ambient temperature when fully hydrated. Cysts have adapted to stress in several ways; they are surrounded by a rigid cell wall impermeable to most chemical compounds and which functions as a shield against ultraviolet radiation. Artemia cysts contain large amounts of trehalose, a non-reducing sugar thought to preserve membranes and proteins during desiccation by replacing water molecules and/or contributing to vitrification. Late embryogenesis abundant proteins similar to those in seeds and other anhydrobiotic organisms are found in cysts, and they safeguard cell organelles and proteins during desiccation. Artemia cysts contain abundant amounts of p26, a small heat shock protein, and artemin, a ferritin homologue, both ATP-independent molecular chaperones important in stress tolerance. The evidence provided in this review supports the conclusion that it is the interplay of these protective elements that make Artemia one of the most stress tolerant of all metazoan organisms.

PHYSICO2: an UNIX based standalone procedure for computation of physicochemical, window-dependent and substitution based evolutionary properties of protein sequences along with automated block preparation tool, version 2

Automated genome sequencing procedure is enriching the sequence database very fast. To achieve a balance between the entry of sequences in the database and their analyses, efficient software is required. In this end PHYSICO2, compare to earlier PHYSICO and other public domain tools, is most efficient in that it i] extracts physicochemical, window-dependent and homologousposition-based-substitution (PWS) properties including positional and BLOCK-specific diversity and conservation, ii] provides users with optional-flexibility in setting relevant input-parameters, iii] helps users to prepare BLOCK-FASTA-file by the use of Automated Block Preparation Tool of the program, iv] performs fast, accurate and user-friendly analyses and v] redirects itemized outputs in excel format along with detailed methodology. The program package contains documentation describing application of methods. Overall the program acts as efficient PWS-analyzer and finds application in sequence-bioinformatics.

AVAILABILITY

PHYSICO2: is freely available at http://sourceforge.net/projects/physico2/ along with its documentation at https://sourceforge.net/projects/physico2/files/Documentation.pdf/download for all users.

Variability within a pea core collection of LEAM and HSP22, two mitochondrial seed proteins involved in stress tolerance

LEAM, a late embryogenesis abundant protein, and HSP22, a small heat shock protein, were shown to accumulate in the mitochondria during pea (Pisum sativum L.) seed development, where they are expected to contribute to desiccation tolerance. Here, their expression was examined in seeds of 89 pea genotypes by Western blot analysis. All genotypes expressed LEAM and HSP22 in similar amounts. In contrast with HSP22, LEAM displayed different isoforms according to apparent molecular mass. Each of the 89 genotypes harboured a single LEAM isoform. Genomic and RT-PCR analysis revealed four LEAM genes differing by a small variable indel in the coding region. These variations were consistent with the apparent molecular mass of each isoform. Indels, which occurred in repeated domains, did not alter the main properties of LEAM. Structural modelling indicated that the class A α-helix structure, which allows interactions with the mitochondrial inner membrane in the dry state, was preserved in all isoforms, suggesting functionality is maintained. The overall results point out the essential character of LEAM and HSP22 in pea seeds. LEAM variability is discussed in terms of pea breeding history as well as LEA gene evolution mechanisms.

Comparison of amino acids physico-chemical properties and usage of late embryogenesis abundant proteins, hydrophilins and WHy domain

Late Embryogenesis Abundant proteins (LEAPs) comprise several diverse protein families and are mostly involved in stress tolerance. Most of LEAPs are intrinsically disordered and thus poorly functionally characterized. LEAPs have been classified and a large number of their physico-chemical properties have been statistically analyzed. LEAPs were previously proposed to be a subset of a very wide family of proteins called hydrophilins, while a domain called WHy (Water stress and Hypersensitive response) was found in LEAP class 8 (according to our previous classification). Since little is known about hydrophilins and WHy domain, the cross-analysis of their amino acids physico-chemical properties and amino acids usage together with those of LEAPs helps to describe some of their structural features and to make hypothesis about their function. Physico-chemical properties of hydrophilins and WHy domain strongly suggest their role in dehydration tolerance, probably by interacting with water and small polar molecules. The computational analysis reveals that LEAP class 8 and hydrophilins are distinct protein families and that not all LEAPs are a protein subset of hydrophilins family as proposed earlier. Hydrophilins seem related to LEAP class 2 (also called dehydrins) and to Heat Shock Proteins 12 (HSP12). Hydrophilins are likely unstructured proteins while WHy domain is structured. LEAP class 2, hydrophilins and WHy domain are thus proposed to share a common physiological role by interacting with water or other polar/charged small molecules, hence contributing to dehydration tolerance.

Molecular analysis of the cold tolerant Antarctic nematode, Panagrolaimus davidi

Isolated and established in culture from the Antarctic in 1988, the nematode Panagrolaimus davidi has proven to be an ideal model for the study of adaptation to the cold. Not only is it the best-documented example of an organism surviving intracellular freezing but it is also able to undergo cryoprotective dehydration. As part of an ongoing effort to develop a molecular understanding of this remarkable organism, we have assembled both a transcriptome and a set of genomic scaffolds. We provide an overview of the transcriptome and a survey of genes involved in temperature stress. We also explore, in silico, the possibility that P. davidi will be susceptible to an environmental RNAi response, important for further functional studies.

The ubiquitous distribution of late embryogenesis abundant proteins across cell compartments in Arabidopsis offers tailored protection against abiotic stress

Late embryogenesis abundant (LEA) proteins are hydrophilic, mostly intrinsically disordered proteins, which play major roles in desiccation tolerance. In Arabidopsis thaliana, 51 genes encoding LEA proteins clustered into nine families have been inventoried. To increase our understanding of the yet enigmatic functions of these gene families, we report the subcellular location of each protein. Experimental data highlight the limits of in silico predictions for analysis of subcellular localization. Thirty-six LEA proteins localized to the cytosol, with most being able to diffuse into the nucleus. Three proteins were exclusively localized in plastids or mitochondria, while two others were found dually targeted to these organelles. Targeting cleavage sites could be determined for five of these proteins. Three proteins were found to be endoplasmic reticulum (ER) residents, two were vacuolar, and two were secreted. A single protein was identified in pexophagosomes. While most LEA protein families have a unique subcellular localization, members of the LEA_4 family are widely distributed (cytosol, mitochondria, plastid, ER, and pexophagosome) but share the presence of the class A α-helix motif. They are thus expected to establish interactions with various cellular membranes under stress conditions. The broad subcellular distribution of LEA proteins highlights the requirement for each cellular compartment to be provided with protective mechanisms to cope with desiccation or cold stress.

Twenty years of research on Asr (ABA-stress-ripening) genes and proteins

Investigating how plants cope with different abiotic stresses-mainly drought and extreme temperatures-is pivotal for both understanding the underlying signaling pathways and improving genetically engineered crops. Plant cells are known to react defensively to mild and severe dehydration by initiating several signal transduction pathways that result in the accumulation of different proteins, sugar molecules and lipophilic anti-oxidants. Among the proteins that build up under these adverse conditions are members of the ancestral ASR (ABA-stress-ripening) family, which is conserved in the plant kingdom but lacks orthologs in Arabidopsis. This review provides a comprehensive summary of the state of the art regarding ASRs, going back to the original description and cloning of the tomato ASR cDNA. That seminal discovery sparked worldwide interest amongst research groups spanning multiple fields: biochemistry, cell biology, evolution, physiology and epigenetics. As these proteins function as both chaperones and transcription factors; this review also covers the progress made on relevant molecular features that account for these dual roles-including the recent identification of their target genes-which may inspire future basic research. In addition, we address reports of drought-tolerant ASR-transgenic plants of different species, highlighting the influential work of authors taking more biotechnological approaches.

Multifarious roles of intrinsic disorder in proteins illustrate its broad impact on plant biology

Intrinsically disordered proteins (IDPs) are highly abundant in eukaryotic proteomes. Plant IDPs play critical roles in plant biology and often act as integrators of signals from multiple plant regulatory and environmental inputs. Binding promiscuity and plasticity allow IDPs to interact with multiple partners in protein interaction networks and provide important functional advantages in molecular recognition through transient protein-protein interactions. Short interaction-prone segments within IDPs, termed molecular recognition features, represent potential binding sites that can undergo disorder-to-order transition upon binding to their partners. In this review, we summarize the evidence for the importance of IDPs in plant biology and evaluate the functions associated with intrinsic disorder in five different types of plant protein families experimentally confirmed as IDPs. Functional studies of these proteins illustrate the broad impact of disorder on many areas of plant biology, including abiotic stress, transcriptional regulation, light perception, and development. Based on the roles of disorder in the protein-protein interactions, we propose various modes of action for plant IDPs that may provide insight for future experimental approaches aimed at understanding the molecular basis of protein function within important plant pathways.

Experimental determination of organelle targeting-peptide cleavage sites using transient expression of green fluorescent protein translational fusions

The majority of nuclear-encoded organellar proteins contain a cleavable presequence, which is necessary for protein targeting and import into the correct cellular compartment. Knowledge about targeting-peptide cleavage sites is essential for the structural and functional characterization of the mature organellar proteins as well as for a deeper understanding of the import process. Because of the low consensus and high variability of presequences, bioinformatics of targeting-peptide cleavage fails to predict the length of the targeting peptide with high confidence. Therefore, we have developed a rapid and robust method to experimentally determine the cleavage site of the transit peptide for proteins imported into mitochondria or plastids. The protein precursor with green fluorescent protein (GFP) fused to its C-terminus is transiently expressed in cells (for animal proteins) or protoplasts (for plant proteins), allowing translocation into organelles and removal of the transit peptide. After lysis, the matured protein is immunopurified using an anti-GFP antibody coupled to magnetic beads. The N-terminal amino sequence is then determined by Edman microsequencing or mass spectrometry. The method has been validated using proteins with known targeting-peptide sequences and is suitable for animal and plant organelle-targeted proteins.