The effect of Fusarium culmorum infection and deoxynivalenol (DON) application on proteome response in barley cultivars Chevron and Pedant

TcSERPIN, an inhibitor that interacts with cocoa defense proteins and has biotechnological potential against human pathogens

In plants, serpins are a superfamily of serine and cysteine protease inhibitors involved in stress and defense mechanisms, with potential for controlling agricultural pests, making them important biotechnological tools. The objective of this study was to characterize a serpin from Theobroma cacao, called TcSERPIN, to identify its endogenous targets and determine its function and biotechnological potential. TcSERPIN has 390 amino acid residues and shows conservation of the main active site, RCL. Cis-elements related to light, stress, hormones, anaerobic induction, cell cycle regulation and defense have been identified in the gene's regulatory region. TcSERPIN transcripts are accumulated in different tissues of Theobroma cacao. Furthermore, in plants infected with Moniliophtora perniciosa and Phytophthora palmivora, the expression of TcSERPIN was positively regulated. The protein spectrum, rTcSERPIN, reveals a typical β-sheet pattern and is thermostable at pH 8, but loses its structure with temperature increases above 66°C at pH 7. At the molar ratios of 0.65 and 0.49, rTcSERPIN inhibited 55 and 28% of the activity of papain from Carica papaya and trypsin from Sus scrofa, respectively. The protease trap containing immobilized rTcSERPIN captured endogenous defense proteins from cocoa extracts that are related to metabolic pathways, stress and defense. The evaluation of the biotechnological potential against geohelminth larvae showed that rTcSERPIN and rTcCYS4 (Theobroma cacao cystatin 4) reduced the movement of larvae after 24 hours. The results of this work show that TcSERPIN has ideal biochemical characteristics for biotechnological applications, as well as potential for studies of resistance to phytopathogens of agricultural crops.

Plant Serpins: Potential Inhibitors of Serine and Cysteine Proteases with Multiple Functions

Plant serpins are a superfamily of protein inhibitors that have been continuously studied in different species and have great biotechnological potential. However, despite ongoing studies with these inhibitors, the biological role of this family in the plant kingdom has not yet been fully clarified. In order to obtain new insights into the potential of plant serpins, this study presents the first systematic review of the topic, whose main objective was to scrutinize the published literature to increase knowledge about this superfamily. Using keywords and the eligibility criteria defined in the protocol, we selected studies from the Scopus, PubMed, and Web of Science databases. According to the eligible studies, serpins inhibit different serine and non-serine proteases from plants, animals, and pathogens, and their expression is affected by biotic and abiotic stresses. Moreover, serpins like AtSerpin1, OSP-LRS, MtSer6, AtSRP4, AtSRP5, and MtPiI4, act in resistance and are involved in stress-induced cell death in the plant. Also, the system biology analysis demonstrates that serpins are related to proteolysis control, cell regulation, pollen development, catabolism, and protein dephosphorylation. The information systematized here contributes to the design of new studies of plant serpins, especially those aimed at exploring their biotechnological potential.

Untargeted Metabolomics Reveals a Multi-Faceted Resistance Response to Fusarium Head Blight Mediated by the Thinopyrum elongatum Fhb7E Locus Transferred via Chromosome Engineering into Wheat

The Thinopyrum elongatum Fhb7E locus has been proven to confer outstanding resistance to Fusarium Head Blight (FHB) when transferred into wheat, minimizing yield loss and mycotoxin accumulation in grains. Despite their biological relevance and breeding implications, the molecular mechanisms underlying the resistant phenotype associated with Fhb7E have not been fully uncovered. To gain a broader understanding of processes involved in this complex plant-pathogen interaction, we analysed via untargeted metabolomics durum wheat (DW) rachises and grains upon spike inoculation with Fusarium graminearum (Fg) and water. The employment of DW near-isogenic recombinant lines carrying or lacking the Th. elongatum chromosome 7E region including Fhb7E on their 7AL arm, allowed clear-cut distinction between differentially accumulated disease-related metabolites. Besides confirming the rachis as key site of the main metabolic shift in plant response to FHB, and the upregulation of defence pathways (aromatic amino acid, phenylpropanoid, terpenoid) leading to antioxidants and lignin accumulation, novel insights were revealed. Fhb7E conferred constitutive and early-induced defence response, in which specific importance of polyamine biosynthesis, glutathione and vitamin B6 metabolisms, along with presence of multiple routes for deoxynivalenol detoxification, was highlighted. The results suggested Fhb7E to correspond to a compound locus, triggering a multi-faceted plant response to Fg, effectively limiting Fg growth and mycotoxin production.

Proteomic responses of two spring wheat cultivars to the combined water deficit and aphid (Metopolophium dirhodum) treatments

In the field, plants usually have to face the combined effects of abiotic and biotic stresses. In our study, two spring wheat cultivars-Septima and Quintus-were subjected to three water regimes [70%, 50%, and 40% soil water capacity (SWC)], aphid (Metopolophium dirhodum) infestation, or the combination of both stresses, i.e., water deficit (50%, 40% SWC) and aphids. The study has a 2 × 3 × 2 factorial design with three biological replicates. In the present study, the results of proteomic analysis using 2D-DIGE followed by MALDI-TOF/TOF protein identification are presented. Water deficit but also aphid infestation led to alterations in 113 protein spots including proteins assigned to a variety of biological processes ranging from signaling via energy metabolism, redox regulation, and stress and defense responses to secondary metabolism indicating a long-term adaptation to adverse conditions. The absence of specific proteins involved in plant response to herbivorous insects indicates a loss of resistance to aphids in modern wheat cultivars during the breeding process and is in accordance with the "plant vigor hypothesis." Septima revealed enhanced tolerance with respect to Quintus as indicated by higher values of morphophysiological characteristics (fresh aboveground biomass, leaf length, osmotic potential per full water saturation) and relative abundance of proteins involved in mitochondrial respiration and ATP biosynthesis.

Proteome-Wide Response of Dormant Caryopses of the Weed, Avena fatua, After Colonization by a Seed-Decay Isolate of Fusarium avenaceum

Promoting seed decay is an ecological approach to reducing weed persistence in the soil seedbank. Previous work demonstrated that Fusarium avenaceum F.a.1 decays dormant Avena fatua (wild oat) caryopses and induces several defense enzyme activities in vitro. The objectives of this study were to obtain a global perspective of proteins expressed after F.a.1-caryopsis colonization by conducting proteomic evaluations on (i) leachates, soluble extrinsic (seed-surface) proteins released upon washing caryopses in buffer and (ii) proteins extracted from whole caryopses; interactions with aluminum (Al) were also evaluated in the latter study because soil acidification and associated metal toxicity are growing problems. Of the 119 leachate proteins classified as defense/stress, 80 were induced or repressed. Defense/stress proteins were far more abundant in A. fatua (35%) than in F.a.1 (12%). Avena defense/stress proteins were also the most highly regulated category, with 30% induced and 35% repressed by F.a.1. Antifungal proteins represented 36% of Avena defense proteins and were the most highly regulated, with 36% induced and 37% repressed by F.a.1. These results implicate selective regulation of Avena defense proteins by F.a.1. Fusarium proteins were also highly abundant in the leachates, with 10% related to pathogenicity, 45% of which were associated with host cell wall degradation. In whole caryopsis extracts, fungal colonization generally resulted in induction of a similar set of Avena proteins in the presence and absence of Al. Results advance the hypothesis that seed decay pathogens elicit intricate and dynamic biochemical responses in dormant seeds.

Membrane Proteins and Proteomics of Cronobacter sakazakii Cells: Reliable Method for Identification and Subcellular Localization

Members of the genus Cronobacter are responsible for severe infections in infants and immunosuppressed individuals. Although several virulence factors have been described, many proteins involved in the pathogenesis of such infections have not yet been mapped. This study is the first to fractionate Cronobacter sakazakii cells into outer membrane, inner membrane, periplasmic, and cytosolic fractions as the basis for improved proteome mapping. A novel method was designed to prepare the fractionated samples for protein identification. The identification was performed via one-dimensional electrophoresis-liquid chromatography electrospray ionization tandem mass spectrometry. To determine the subcellular localization of the identified proteins, we developed a novel Python-based script (Subcelloc) that combines three web-based tools, PSORTb 3.0.2, CELLO 2.5, and UniProtKB. Applying this approach enabled us to identify 1,243 C. sakazakii proteins, which constitutes 28% of all predicted proteins and 49% of all theoretically expressed outer membrane proteins. These results represent a significant improvement on previous attempts to map the C. sakazakii proteome and could provide a major step forward in the identification of Cronobacter virulence factors. IMPORTANCE Cronobacter spp. are opportunistic pathogens that can cause rare and, in many cases, life-threatening infections, such as meningitis, necrotizing enterocolitis, and sepsis. Such infections are mainly linked to the consumption of contaminated powdered infant formula, with Cronobacter sakazakii clonal complex 4 considered the most frequent agent of serious neonatal infection. However, the pathogenesis of diseases caused by these bacteria remains unclear; in particular, the proteins involved throughout the process have not yet been mapped. To help address this, we present an improved method for proteome mapping that emphasizes the isolation and identification of membrane proteins. Specific focus was placed on the identification of the outer membrane proteins, which, being exposed to the surface of the bacterium, directly participate in host-pathogen interaction.

Plant proteomic research for improvement of food crops under stresses: a review

Crop improvement approaches have been changed due to technological advancements in traditional plant-breeding methods. Abiotic and biotic stresses limit plant growth and development, which ultimately lead to reduced crop yield. Proteins encoded by genomes have a considerable role in the endurance and adaptation of plants to different environmental conditions. Biotechnological applications in plant breeding depend upon the information generated from proteomic studies. Proteomics has a specific advantage to contemplate post-translational modifications, which indicate the functional effects of protein modifications on crop production. Subcellular proteomics helps in exploring the precise cellular responses and investigating the networking among subcellular compartments during plant development and biotic/abiotic stress responses. Large-scale mass spectrometry-based plant proteomic studies with a more comprehensive overview are now possible due to dramatic improvements in mass spectrometry, sample preparation procedures, analytical software, and strengthened availability of genomes for numerous plant species. Development of stress-tolerant or resilient crops is essential to improve crop productivity and growth. Use of high throughput techniques with advanced instrumentation giving efficient results made this possible. In this review, the role of proteomic studies in identifying the stress-response processes in different crops is summarized. Advanced techniques and their possible utilization on plants are discussed in detail. Proteomic studies accelerate marker-assisted genetic augmentation studies on crops for developing high yielding stress-tolerant lines or varieties under stresses.

Proteomics Reveals the Changes that Contribute to Fusarium Head Blight Resistance in Wheat

Fusarium head blight (FHB) is a devastating disease of wheat, causing yield losses and quality reduction as a result of mycotoxin production. In this study, iTRAQ (isobaric tags for relative and absolute quantification)-labeling-based mass spectrometry was employed to characterize the proteome in wheat cultivars Xinong 538 and Zhoumai 18 with contrasting levels of FHB resistance as a means to elucidate the molecular mechanisms contributing to FHB resistance. A total of 13,669 proteins were identified in the two cultivars 48 h after Fusarium graminearum inoculation. Among these, 2,505 unique proteins exclusively accumulated in Xinong 538 (resistant) and 887 proteins in Zhoumai 18 (susceptible). Gene Ontology enrichment analysis showed that most differentially accumulated proteins (DAPs) from both cultivars were assigned to the following categories: metabolic process, single-organism process, cellular process, and response to stimulus. Kyoto Encyclopedia of Genes and Genomes analysis showed that a greater number of proteins belonging to different metabolic pathways were identified in Xinong 538 compared with Zhoumai 18. Specifically, DAPs from the FHB-resistant cultivar Xinong 538 populated categories of metabolic pathways related to plant-pathogen interaction. These DAPs might play a critical role in defense responses exhibited by Xinong 538. DAPs from both genotypes were assigned to all wheat chromosomes except chromosome 6B, with approximately 30% mapping to wheat chromosomes 2B, 3B, 5B, and 5D. Twenty single nucleotide polymorphism markers, flanking DAPs on chromosomes 1B, 3B, 5B, and 6A, overlapped with the location of earlier mapped FHB-resistance quantitative trait loci. The data provide evidence for the involvement of several DAPs in the early stages of the FHB-resistance response in wheat; however, further functional characterization of candidate proteins is warranted.

Relationship between the Content of β-D-Glucans and Infection with Fusarium Pathogens in Oat (Avena sativa L.) Plants

In human nutrition, oats (Avena sativa L.) are mainly used for their dietary fiber, β-D-glucans and protein content. The content of β-D-glucans in oat grain is 2-7% and is influenced by genetic and/or environmental factors. High levels of this cell walls polysaccharide are observed in naked grains of cultivated oat. It the work, the relationship between the content of β-D-glucans in oat grain and the infection with Fusarium graminearum (FG) and Fusarium culmorum (FC) was analyzed. The hypothesis was that oats with higher content of β-D-glucans are better protected and the manifestation of artificial inoculation with Fusarium strains is weaker. In the 22 oat samples analyzed, the content of β-D-glucans was 0.71-5.06%. In controls, the average content was 2.15% for hulled and 3.25% for naked grains of cultivated oats. After the infection, a decrease was observed in all, naked, hulled and wild oats. As an evidence of lower rate of infection, statistically significant lower percentage of pathogen DNA (0.39%) and less deoxynivalenol (DON) mycotoxin (FC infection 10.66 mg/kg and FG 4.92 mg/kg) were observed in naked grains compared to hulled where the level of pathogen DNA was 2.09% and the average DON level was 21.95 mg/kg (FC) and 5.52 mg/kg (FG).

Nitrogen deprivation in Fusarium oxysporum promotes mycotoxin production via intermediates in the Krebs cycle and unreported methylmalonyl-CoA mutase activity

INTRODUCTION

Fusarium oxysporum has a high affinity for lignin and cellulose-based substrates and is known to grow in a wide range of environments. It is these properties and its ability to produce mycotoxins that have contributed to its pathogenicity in cereal crops that can affect human and animal health when ingested.

OBJECTIVES

Identify the mechanisms of mycotoxin production and map the functional output of F. oxysporum under varying growth conditions.

METHODS

Liquid and gas-based chromatography coupled with mass spectrometry was used to identify and map the untargeted metabolic pathway of F. oxysporum grown using nitrogen limited and organic/inorganic nitrogen supplemented media.

RESULTS

Over 1300 metabolites were identified, relating to 42 metabolic pathways. Of these, 520 metabolites merged at pyruvate (glycolysis), succinate (Krebs cycle) and aspartate-glutamate metabolic pathways. CoA depletion at the growth stage triggered the initiation of fatty acid and branched amino acid degradation. This in turn activated propionyl CoA carnitine acetyltransferase enzymes, resulting in nitrogen preservation (urea, putrescine and organic acids end-products). CoA then transferred into the TCA cycle via previously unreported β-alanine and propionyl CoA metabolic pathways, the latter likely being a novel methylmalonyl-CoA mutase activity for F. oxysporum.

CONCLUSIONS

The lower supplementation of inorganic nitrogen compounds (≤ 50 mM) and the elimination of nitrates/organic nitrogen sources resulted in TCA autophagy events that boosted mycotoxin-based metabolism and decreased overall F. oxysporum growth. Such knowledge of functional mycotoxin production can be used to supplement agricultural crops and reduce the risk of mycotoxin contamination in human and animal food supplies.