Isolation of a large thaumatin-like antifungal protein from seeds of the Kweilin chestnut Castanopsis chinensis

Genome-wide analysis and characterization of the TaTLP gene family in wheat and functional characterization of the TaTLP44 in response to Rhizoctonia cerealis

Wheat sharp eyespot is a soil-borne disease caused by Rhizoctonia cerealis, which occurs in many countries worldwide and significantly reduces the yield. Thaumatin-like protein (TLP), also known as PR5, is a member of the pathogen response protein family and plays an essential role in plant resistance to pathogen infection. In this study, 131 TaTLP genes were identified from the wheat genome, of which 38 TaTLPs were newly discovered. The TaTLP gene family contains many tandem duplications and fragment duplications, which is a major pathway for gene amplification. Besides, we also analyzed the physicochemical properties, gene structure and promoter cis-acting regulatory elements of all the TaTLP genes. In addition, the expression patterns of nine TaTLPs in response to R. cerealis were analyzed by RT-qPCR. Six TaTLP proteins expressed in vitro had no significant inhibitory effect on R. cerealis, suggesting that these TaTLP proteins may function in other ways. Finally, we performed gene silencing of TaTLP44 in wheat, which increased the expression of some defense-associated genes and improved resistance to R. cerealis. In summary, we systematically analyzed TaTLP family members and demonstrated that TaTLP44 negatively regulates the resistance to R. cerealis by controlling expression of defense-associated genes. These results provide new insights into the functional mechanism of TaTLP proteins.

Towards Biological Control of Aspergillus carbonarius and Botrytis cinerea in Grapevine Berries and Transcriptomic Changes of Genes Encoding Pathogenesis-Related (PR) Proteins

Grapevine bunch rot, caused by Botrytis cinerea and Aspergillus carbonarius, causes important economic losses every year in grape production. In the present study, we examined the plant protective activity of the biological control agents, Paenibacillus alvei K165, Blastobotrys sp. FP12 and Arthrobacter sp. FP15 against B. cinerea and A. carbonarius on grapes. The in vitro experiments showed that strain K165 significantly reduced the growth of both fungi, while FP15 restricted the growth of A. carbonarius and FP12 was ineffective. Following the in vitro experiments, we conducted in planta experiments on grape berries. It was shown that K165, FP12 and FP15 reduced A. carbonarius rot severity by 81%, 57% and 37%, respectively, compared to the control, whereas, in the case of B. cinerea, the only protective treatment was that with K165, which reduced rot by 75%. The transcriptomic analysis of the genes encoding the pathogenesis-related proteins PR2, PR3, PR4 and PR5 indicates the activation of multiple defense responses involved in the biocontrol activity of the examined biocontrol agents.

Characterization of black spot resistance in diploid roses with QTL detection, meta-analysis and candidate-gene identification

Two environmentally stable QTLs linked to black spot disease resistance in the Rosa wichurana genetic background were detected, in different connected populations, on linkage groups 3 and 5. Co-localization between R-genes and defense response genes was revealed via meta-analysis. The widespread rose black spot disease (BSD) caused by the hemibiotrophic fungus Diplocarpon rosae Wolf. is efficiently controlled with fungicides. However, in the actual context of reducing agrochemical use, the demand for rose bushes with higher levels of resistance has increased. Qualitative resistance conferred by major genes (Rdr genes) has been widely studied but quantitative resistance to BSD requires further investigation. In this study, segregating populations connected through the BSD resistant Rosa wichurana male parent were phenotyped for disease resistance over several years and locations. A pseudo-testcross approach was used, resulting in six parental maps across three populations. A total of 45 individual QTLs with significant effect on BSD resistance were mapped on the male maps (on linkage groups (LG) B3, B4, B5 and B6), and 12 on the female maps (on LG A1, A2, A3, A4 and A5). Two major regions linked to BSD resistance were identified on LG B3 and B5 of the male maps and were integrated into a consensus map built from all three of the male maps. A meta-analysis was used to narrow down the confidence intervals of individual QTLs from three populations by generating meta-QTLs. Two 'hot spots' or meta-QTLs were found per LG, enabling reduction of the confidence interval to 10.42 cM for B3 and 11.47 cM for B5. An expert annotation of NBS-LRR encoding genes of the genome assembly of Hibrand et al. was performed and used to explore potential co-localization with R-genes. Co-localization with defense response genes was also investigated.

TLPdb: A Resource for Thaumatin-Like Proteins

Antifungal proteins and peptides have drawn the attention of numerous plant biologists and Clinicians, owing to their potential value in protecting commercial crops as well as preventing fungal infections in humans. Various proteins and peptides, such as glucanases, chitinases, chitinase-like proteins, lectins, peroxidases, defensins, and lipid transfer proteins have antifungal activities. Thaumatin is a protein from a West African plant Thaumatococcus danielli that is sweet in taste but does not exhibit antifungal activities. Despite the structural similarities between thaumatins and thaumatin-like proteins (TLPs), TLPs are not sweet in taste, unlike thaumatins. We developed a thaumatin-like protein database of various organisms. TLPs are pathogenesis-related proteins (PR) with molecular masses of 20-26 kDa. The amino acid residues of TLPs involved in an antifungal activity remain obscure and make it hard to receive comprehensive information on TLPs. The biggest problem in the wine industry is white haze, an undesirable feature of high-quality wine. Hence, the problem may be figured out with the easy accessibility of amino acid sequences and to generate infest resistant crops. Overall, we aimed to produce a freely accessible TLP database ( https://tlpdb.cftri.com ) that would provide substantive information in understanding the mechanistic facet of TLPs. Briefly, TLPdb contains sequences, structures, and amino acid compositions of validated, published TLP protein sequences (from the plant, fungal as well as animal sources). Thus, this work may yield valuable information that may be useful in understanding the mechanistic aspects of TLP activity and in the evolution of antifungal proteins and fungal resistant crops. TLPdb is a comprehensive thaumatin-like protein resource database of various organisms. The database can serve as a unique Bioinformatics tool for understanding the TLPs. This further may help in understanding and the development of fungal resistant crops. TLPdb is freely available at https://tlpdb.cftri.com .

Structure-Activity-Relationship and Mechanistic Insights for Anti-HIV Natural Products

Acquired Immunodeficiency Syndrome (AIDS), which chiefly originatesfroma retrovirus named Human Immunodeficiency Virus (HIV), has impacted about 70 million people worldwide. Even though several advances have been made in the field of antiretroviral combination therapy, HIV is still responsible for a considerable number of deaths in Africa. The current antiretroviral therapies have achieved success in providing instant HIV suppression but with countless undesirable adverse effects. Presently, the biodiversity of the plant kingdom is being explored by several researchers for the discovery of potent anti-HIV drugs with different mechanisms of action. The primary challenge is to afford a treatment that is free from any sort of risk of drug resistance and serious side effects. Hence, there is a strong demand to evaluate drugs derived from plants as well as their derivatives. Several plants, such as Andrographis paniculata, Dioscorea bulbifera, Aegle marmelos, Wistaria floribunda, Lindera chunii, Xanthoceras sorbifolia and others have displayed significant anti-HIV activity. Here, weattempt to summarize the main results, which focus on the structures of most potent plant-based natural products having anti-HIV activity along with their mechanisms of action and IC50 values, structure-activity-relationships and important key findings.

Differential interaction of the dark septate endophyte Cadophora sp. and fungal pathogens in vitro and in planta

Dark septate endophytes (DSEs) present a group of widespread root-colonizing fungi. The role of these endophytes in ecosystems and their interactions with plant pathogens are not well understood. In the current study, we assessed the antagonistic potential of the model DSE Cadophora sp. against the tomato soilborne pathogens Rhizoctonia solani, Pythium aphanidermatum and Verticillium dahliae. To investigate their interactions, we conducted in vitro assays followed by a greenhouse experiments in which tomato plants were inoculated with different combinations of the DSE and pathogens. RNA accumulation of selected tomato pathogenesis-related genes and of Cadophora sp. genes with putative antifungal function was analyzed. Cadophora sp. inhibited the growth of the fungal pathogens in vitro and vice versa; a negative impact of the pathogens on the growth of the DSE was also detected. In roots, however, this mutual negative interaction could not be observed. Expression analyses of plant genes could not explain this differential effect, but among the Cadophora sp. genes analyzed, a gene coding for a chalcone synthase was downregulated in planta. The data indicate that plants can change the interaction between fungi and, therefore, in vitro detected antagonism does not necessarily reflect the situation inside the plant.

Mining the effector repertoire of the biotrophic fungal pathogen Ustilago hordei during host and non-host infection

The success of plant-pathogenic fungi mostly relies on their arsenal of virulence factors which are expressed and delivered into the host tissue during colonization. The biotrophic fungal pathogen Ustilago hordei causes covered smut disease on both barley and oat. In this study, we combined cytological, genomics and molecular biological methods to achieve a better understanding of the molecular interactions in the U. hordei-barley pathosystem. Microscopic analysis revealed that U. hordei densely colonizes barley leaves on penetration, in particular the vascular system. Transcriptome analysis of U. hordei at different stages of host infection revealed differential expression of the transcript levels of 273 effector gene candidates. Furthermore, U. hordei transcriptionally activates core effector genes which may suppress even non-host early defence responses. Based on expression profiles and novelty of sequences, knockout studies of 14 effector candidates were performed in U. hordei, which resulted in the identification of four virulence factors required for host colonization. Yeast two-hybrid screening identified potential barley targets for two of the effectors. Overall, this study provides a first systematic analysis of the effector repertoire of U. hordei and identifies four effectors (Uvi1-Uvi4) as virulence factors for the infection of barley.

Gene Cloning, Expression, and Antifungal Activities of Permatin from Naked Oat (Avena nuda)

Thaumatin-like proteins (TLPs) are the products of a large, highly complex gene family involved in host defense. TLPs also belong to the pathogenesis-related family 5 (PR-5) of plant defense proteins. Most TLPs exhibit potential antifungal activities, and their accumulation in the plant is related to many physiological processes. In this study, a gene encoding TLP named permatin with an open reading frame of 678 bp encoding a protein of 225 amino acids with a calculated molecular mass of 23.5 kDa was cloned from naked oat leaves. Phylogenetic analysis revealed that permatin shares high homology with a number of other TLPs among diverse taxa. Model of structure by homology modeling showed that permatin consists of an acidic cleft region consistent with most TLPs. Recombinant NusA-permatin was overexpressed in Escherichia coli strain BL21 and purified by Heparin column combined with Sephacryl S-200 column. The protein exhibited antifungal activity to Fusarium oxysporum (half maximal inhibitory concentration, IC₅₀ = 21.42 μM). Morphological observation showed that NusA-permatin can induce mycelium deformation of F. oxysporum, the cell membrane is blurred, and the diaphragm is not obvious. NusA-permatin also causes membrane permeabilization and reactive oxygen species accumulation in the mycelium of F. oxysporum. Permatin may play an important role in the disease resistance responses of plants against pathogen attacks through its antifungal activity.

A thaumatin-like genomic sequence identification in Vitis vinifera l., stormy wines and musts based on direct pcr

Direct polymerase chain reaction method was use to amplify a thaumatin-like sequence of Vitis vinifera L. in grapes as well as in stormy wines and musts. Thaumatin-like proteins (TLPs) of Vitis vinifera possess beside its function in abiotic and biotic stress response another one - they are able to cause protein haze in wine unless removed prior to bottling. Direct PCR is an approach where omission of DNA extraction is typical prior the amplification of the target site of plant genome. Crude extract or small pieces of plant tissues are used in the analysis directly without steps of extraction and purification of gDNA. The biological material that was used in analysis was collected during August - October 2017 in local stores and winery Sabo and comprises from cultivars Iršai, Muškát, Savignon Blanc, Svätovavrinecké, Dornfelder and Pálava. Direct PCR was performed by a cutted piece of grape tissue and a dilution buffer was use in 1:2 for stormy wine or must, respectively. Direct amplification of thaumatin-like protein sequence of Vitis vinifera was performed along with the control reactions with the primers for conserved region of plant chloroplast. Possitive amplification of thaumatin-like allergen sequence resulted in 570 bp amplicon. The most abundant amplicons were amplified in stormy wines, followed by musts and the amplicons from grapes were weaker when comparing them to others. The amplicon specificity checking of obtained PCR product of thaumatin-like allergen was performed by restriction cleavage by Psi I and resulted in restriction amplicons of the 80 bp, 81 bp, 94 bp and 315 bp in length. Confirmation of the amplicon specificity by restriction cleavage support the potential of direct PCR to become a reproducible method that will be fully applicable in routine analysis of not only plant genomes in the future, but it was demonstrated, that it works in liquids, too. 

Bark and wood tissues of American elm exhibit distinct responses to Dutch elm disease

Tolerance to Dutch elm disease (DED) has been linked to the rapid and/or high induction of disease-responsive genes after infection with the fungus Ophiostoma novo-ulmi. Although the fungal infection by O. novo-ulmi primarily takes places in xylem vessels, it is still unclear how xylem contributes to the defense against DED. Taking advantage of the easy separation of wood and bark tissues in young American elm saplings, here we show that most disease-responsive genes exhibited higher expression in wood compared to bark tissues after fungal infection. On the other hand, the stress-related phytohormones were generally more abundant in the bark compared to wood tissues. However, only endogenous levels of jasmonates (JAs), but not salicylic acid (SA) and abscisic acid (ABA) increased in the inoculated tissues. This, along with the upregulation of JA-biosynthesis genes in inoculated bark and core tissues further suggest that phloem and xylem might contribute to the de novo biosynthesis of JA after fungal infection. The comparison between two tolerant elm varieties, 'Valley Forge' and 'Princeton,' also indicated that tolerance against DED might be mediated by different mechanisms in the xylem. The present study sheds some light on the amplitude and kinetics of defense responses produced in the xylem and phloem in response to DED.

Analysis of the grape (Vitis vinifera L.) thaumatin-like protein (TLP) gene family and demonstration that TLP29 contributes to disease resistance

Thaumatin-like protein (TLP) is present as a large family in plants, and individual members play different roles in various responses to biotic and abiotic stresses. Here we studied the role of 33 putative grape (Vitis vinifera L.) TLP genes (VvTLP) in grape disease resistance. Heat maps analysis compared the expression profiles of 33 genes in disease resistant and susceptible grape species infected with anthracnose (Elsinoe ampelina), powdery mildew (Erysiphe necator) or Botrytis cinerea. Among these 33 genes, the expression level of TLP29 increased following the three pathogens inoculations, and its homolog from the disease resistant Chinese wild grape V. quinquangularis cv. 'Shang-24', was focused for functional studies. Over-expression of TLP29 from grape 'Shang-24' (VqTLP29) in Arabidopsis thaliana enhanced its resistance to powdery mildew and the bacterium Pseudomonas syringae pv. tomato DC3000, but decreased resistance to B. cinerea. Moreover, the stomatal closure immunity response to pathogen associated molecular patterns was strengthened in the transgenic lines. A comparison of the expression profiles of various resistance-related genes after infection with different pathogens indicated that VqTLP29 may be involved in the salicylic acid and jasmonic acid/ethylene signaling pathways.

Plant antifungal proteins and their applications in agriculture

Fungi are far more complex organisms than viruses or bacteria and can develop numerous diseases in plants that cause loss of a substantial portion of the crop every year. Plants have developed various mechanisms to defend themselves against these fungi which include the production of low-molecular-weight secondary metabolites and proteins and peptides with antifungal activity. In this review, families of plant antifungal proteins (AFPs) including defensins, lectins, and several others will be summarized. Moreover, the application of AFPs in agriculture will also be analyzed.

Characterization of a pathogen induced thaumatin-like protein gene AdTLP from Arachis diogoi, a wild peanut

Peanut (Arachis hypogaea L) is one of the widely cultivated and leading oilseed crops of the world and its yields are greatly affected by various biotic and abiotic stresses. Arachis diogoi, a wild relative of peanut, is an important source of genes for resistance against various stresses that affect peanut. In our previous study a thaumatin-like protein gene was found to be upregulated in a differential expression reverse transcription PCR (DDRT-PCR) study using the conidial spray of the late leaf spot pathogen, Phaeoisariopsis personata. In the present study, the corresponding full length cDNA was cloned using RACE-PCR and has been designated as AdTLP. It carried an open reading frame of 726 bp potentially capable of encoding a polypeptide of 241 amino acids with 16 conserved cysteine residues. The semi-quantitative RT-PCR analysis showed that the transcript level of AdTLP increased upon treatment with the late leaf spot pathogen of peanut, P. personata and various hormone treatments indicating its involvement in both, biotic and abiotic stresses. The antifungal activity of the purified recombinant protein was checked against different fungal pathogens, which showed enhanced anti-fungal activity compared to many other reported TLP proteins. The recombinant AdTLP-GFP fusion protein was found to be predominantly localized to extracellular spaces. Transgenic tobacco plants ectopically expressing AdTLP showed enhanced resistance to fungal pathogen, Rhizoctonia solani. The seedling assays showed enhanced tolerance of AdTLP transgenic plants against salt and oxidative stress. The transcript analysis of various defense related genes highlighted constitutively higher level expression of PR1a, PI-I and PI-II genes in transgenic plants. These results suggest that the AdTLP is a good candidate gene for enhancing stress resistance in crop plants.

Antimicrobial peptides: key components of the innate immune system

Life-threatening infectious diseases are on their way to cause a worldwide crisis, as treating them effectively is becoming increasingly difficult due to the emergence of antibiotic resistant strains. Antimicrobial peptides (AMPs) form an ancient type of innate immunity found universally in all living organisms, providing a principal first-line of defense against the invading pathogens. The unique diverse function and architecture of AMPs has attracted considerable attention by scientists, both in terms of understanding the basic biology of the innate immune system, and as a tool in the design of molecular templates for new anti-infective drugs. AMPs are gene-encoded short (<100 amino acids), amphipathic molecules with hydrophobic and cationic amino acids arranged spatially, which exhibit broad spectrum antimicrobial activity. AMPs have been the subject of natural evolution, as have the microbes, for hundreds of millions of years. Despite this long history of co-evolution, AMPs have not lost their ability to kill or inhibit the microbes totally, nor have the microbes learnt to avoid the lethal punch of AMPs. AMPs therefore have potential to provide an important breakthrough and form the basis for a new class of antibiotics. In this review, we would like to give an overview of cationic antimicrobial peptides, origin, structure, functions, and mode of action of AMPs, which are highly expressed and found in humans, as well as a brief discussion about widely abundant, well characterized AMPs in mammals, in addition to pharmaceutical aspects and the additional functions of AMPs.

Bactericidal activity identified in 2S Albumin from sesame seeds and in silico studies of structure-function relations

Pathogenic bacteria constitute an important cause of hospital-acquired infections. However, the misuse of available bactericidal agents has led to the appearance of antibiotic-resistant strains. Thus, efforts to seek new antimicrobials with different action mechanisms would have an enormous impact. Here, a novel antimicrobial protein (SiAMP2) belonging to the 2S albumin family was isolated from Sesamum indicum kernels and evaluated against several bacteria and fungi. Furthermore, in silico analysis was conducted in order to identify conserved residues through other 2S albumin antimicrobial proteins (2S-AMPs). SiAMP2 specifically inhibited Klebsiella sp. Specific regions in the molecule surface where cationic (RR/RRRK) and hydrophobic (MEYWPR) residues are exposed and conserved were proposed as being involved in antimicrobial activity. This study reinforces the hypothesis that plant storage proteins might also play as pathogen protection providing an insight into the mechanism of action for this novel 2S-AMP and evolutionary relations between antimicrobial activity and 2S albumins.

Osmotin from Calotropis procera latex: new insights into structure and antifungal properties

This study aimed at investigating the structural properties and mechanisms of the antifungal action of CpOsm, a purified osmotin from Calotropis procera latex. Fluorescence and CD assays revealed that the CpOsm structure is highly stable, regardless of pH levels. Accordingly, CpOsm inhibited the spore germination of Fusarium solani in all pH ranges tested. The content of the secondary structure of CpOsm was estimated as follows: α-helix (20%), β-sheet (33%), turned (19%) and unordered (28%), RMSD 1%. CpOsm was stable at up to 75°C, and thermal denaturation (T(m)) was calculated to be 77.8°C. This osmotin interacted with the negatively charged large unilamellar vesicles (LUVs) of 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-rac-1-glycerol (POPG), inducing vesicle permeabilization by the leakage of calcein. CpOsm induced the membrane permeabilization of spores and hyphae from Fusarium solani, allowing for propidium iodide uptake. These results show that CpOsm is a stable protein, and its antifungal activity involves membrane permeabilization, as property reported earlier for other osmotins and thaumatin-like proteins.

A novel antifungal peptide from foxtail millet seeds

BACKGROUND

Antifungal proteins (AFP) help plants to combat phytopathogenic fungi and thus protect plants from the devastating damage caused by fungal infections and prevent massive economic losses. To date, several proteins with antibacterial and/or antifungal properties have been isolated and characterized from different plant species and tissues; however, there are no reports concerning the antifungal peptide from foxtail millet seeds.

RESULTS

An antifungal peptide with a molecular mass of 26.9 kDa was isolated from dry seeds of the foxtail millet (Setaria italica (L.) Beauv.), using a procedure that involved four chromatographic steps. The antifungal peptide was adsorbed on CM-Sepharose, Affi-gel blue gel and Superdex 75. It was further purified by C(18) reverse-phase high-performance liquid chromatography and submitted for analysis of peptide mass fingerprint. The Mascot peptide mass fingerprint of the isolated protein hit no existing protein (score >60), and it was proved to be a novel antifungal peptide. It inhibited mycelial growth in Alternaria alternate with an IC(50) of 1.3 µmol L(-1) , and it also exhibited antifungal activity against Trichoderma viride, Botrytis cinerea and Fusarium oxysporum. Transmission electron microscopy of mold forms of Alternaria alternate after incubation with 20 µg mL(-1) of the antifungal protein for 48 h revealed marked ultrastructural changes in the fungus.

CONCLUSION

A novel antifungal peptide with high potency was isolated from foxtail millet seeds.

Osmotin purified from the latex of Calotropis procera: biochemical characterization, biological activity and role in plant defense

A protein, similar to osmotin- and thaumatin-like proteins, was purified from Calotropis procera (Ait.) R.Br latex. The isolation procedure required two cation exchange chromatography steps on 50mM Na-acetate buffer (pH 5.0) CM-Sepharose Fast Flow and 25 mM Na-phosphate buffer (pH 6.0) Resource-S, respectively. The protein purity was confirmed by an unique N-terminal sequence [ATFTIRNNCPYTIWAAAVPGGGRRLNSGGTWTINVAPGTA]. The osmotin (CpOsm) appeared as a single band (20,100 Da) in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and as two spots in two-dimensional electrophoresis (pI 8.9 and 9.1). Both polypeptides were further identified by mass spectrometry as two osmotin isoforms with molecular masses of 22,340 and 22,536 Da. The CpOsm exerted antifungal activity against Fusarium solani (IC₅₀=67.0 μg mL⁻¹), Neurospora sp. (IC₅₀=57.5 μg mL⁻¹) and Colletotrichum gloeosporioides (IC₅₀=32.1 μg mL⁻¹). However, this activity was lost when the protein was previously treated with a reducing agent (DTT, Dithiothreitol) suggesting the presence of disulfide bounds stabilizing the protein. The occurrence of osmotin in latex substantiates the defensive role of these fluids.

Purification and characterization of a CkTLP protein from Cynanchum komarovii seeds that confers antifungal activity

BACKGROUND

Cynanchum komarovii Al Iljinski is a desert plant that has been used as analgesic, anthelminthic and antidiarrheal, but also as a herbal medicine to treat cholecystitis in people. We have found that the protein extractions from C. komarovii seeds have strong antifungal activity. There is strong interest to develop protein medication and antifungal pesticides from C. komarovii for pharmacological or other uses.

METHODOLOGY/PRINCIPAL FINDINGS

An antifungal protein with sequence homology to thaumatin-like proteins (TLPs) was isolated from C. komarovii seeds and named CkTLP. The three-dimensional structure prediction of CkTLP indicated the protein has an acid cleft and a hydrophobic patch. The protein showed antifungal activity against fungal growth of Verticillium dahliae, Fusarium oxysporum, Rhizoctonia solani, Botrytis cinerea and Valsa mali. The full-length cDNA was cloned by RT-PCR and RACE-PCR according to the partial protein sequences obtained by nanoESI-MS/MS. The real-time PCR showed the transcription level of CkTLP had a significant increase under the stress of abscisic acid (ABA), salicylic acid (SA), methyl jasmonate (MeJA), NaCl and drought, which indicates that CkTLP may play an important role in response to abiotic stresses. Histochemical staining showed GUS activity in almost the whole plant, especially in cotyledons, trichomes and vascular tissues of primary root and inflorescences. The CkTLP protein was located in the extracellular space/cell wall by CkTLP::GFP fusion protein in transgenic Arabidopsis. Furthermore, over-expression of CkTLP significantly enhanced the resistance of Arabidopsis against V. dahliae.

CONCLUSIONS/SIGNIFICANCE

The results suggest that the CkTLP is a good candidate protein or gene for contributing to the development of disease-resistant crops.

Proteomic profiling of proteins associated with the rejuvenation of Sequoia sempervirens (D. Don) Endl

Background

Restoration of rooting competence is important for rejuvenation in Sequoia sempervirens (D. Don) Endl and is achieved by repeatedly grafting Sequoia shoots after 16 and 30 years of cultivation in vitro.

Results

Mass spectrometry-based proteomic analysis revealed three proteins that differentially accumulated in different rejuvenation stages, including oxygen-evolving enhancer protein 2 (OEE2), glycine-rich RNA-binding protein (RNP), and a thaumatin-like protein. OEE2 was found to be phosphorylated and a phosphopeptide (YEDNFDGNSNVSVMVpTPpTDK) was identified. Specifically, the protein levels of OEE2 increased as a result of grafting and displayed a higher abundance in plants during the juvenile and rejuvenated stages. Additionally, SsOEE2 displayed the highest expression levels in Sequoia shoots during the juvenile stage and less expression during the adult stage. The expression levels also steadily increased during grafting.

Conclusion

Our results indicate a positive correlation between the gene and protein expression patterns of SsOEE2 and the rejuvenation process, suggesting that this gene is involved in the rejuvenation of Sequoia sempervirens.

The superfamily of thaumatin-like proteins: its origin, evolution, and expression towards biological function

Thaumatin-like proteins (TLPs) are the products of a large, highly complex gene family involved in host defence and a wide range of developmental processes in fungi, plants, and animals. Despite their dramatic diversification in organisms, TLPs appear to have originated in early eukaryotes and share a well-defined TLP domain. Nonetheless, determination of the roles of individual members of the TLP superfamily remains largely undone. This review summarizes recent advances made in elucidating the varied TLP activities related to host resistance to pathogens and other physiological processes. Also discussed is the current state of knowledge on the origins and types of TLPs, regulation of gene expression, and potential biotechnological applications for TLPs.

Campesin, a thermostable antifungal peptide with highly potent antipathogenic activities

An 9.4-kDa antifungal peptide designated as campesin was isolated from seeds of the cabbage Brassica campestris. The isolation procedure involved affinity chromatography on Affi-gel blue gel, ion exchange chromatography on Q-Sepharose and Mono S, and gel filtration on Superdex 75 and Superdex Peptide. The peptide was adsorbed on the first three chromatographic media. It exerted an inhibitory action on mycelial growth including Fusarium oxysporum and Mycosphaerella arachidicola, with an IC(50) of 5.1 microM and 4.4 microM, respectively. The peptide was characterized by remarkable thermostability and pH stability. It inhibited proliferation of HepG2 and MCF cancer cells with an IC(50) of 6.4 microM and 1.8 microM, and the activity of HIV-1 reverse transcriptase with an IC(50) of 3.2 microM. It demonstrated lysolecithin binding activity.

Isolation and biochemical characterization of a novel leguminous defense peptide with antifungal and antiproliferative potency

Leguminous plants have formed a popular subject of research owing to the abundance of proteins and peptides with important biological activities that they produce. The antifungal proteins and peptides have been purified from a number of leguminous species. However, research continues to discover novel antifungal plant-produced peptides and proteins are being needed, specially those novel ones with both antifungal activity and other significant bioactivities. The objective of this study was to isolate a novel peptide from Phaseolus limensis. A 6.8 kDa peptide designated Limyin, with both antifungal and antiproliferative activity, was isolated from the large lima bean (P. limensis) legumes. The isolation procedure consisted of extraction, precipitation, affinity chromatography on Affi-gel blue gel, ion chromatography on SP-Toyopearl, and gel filtration on Superdex 75. Its N-terminal sequence was determined to be KTCENLATYYRGPCF, showing high homology to defensin and defensin precursors from plants. It potently suppressed mycelial growth in Alternaria alternata, Fusarium solani, and Botrytis cinerea. Its antifungal activity was stable up to 80 degrees C. It showed antiproliferative activity towards tumor cells including human liver hepatoma cells Bel-7402 and neuroblastoma cells SHSY5Y. However, it had no effect on bacteria Staphylococcus aureus and Salmonella. The present findings make a significant addition of the research on leguminous plants.

Hypotin, a novel antipathogenic and antiproliferative protein from peanuts with a sequence similar to those of chitinase precursors

A protein designated Hypotin, with both antifungal and antibacterial activity, was isolated from peanut (Arachis hypogaea) seeds. The isolation procedure included extraction, ammonium sulfate precipitation, affinity chromatography on Affi-gel blue gel, ion chromatography, and gel filtration. The protein exhibited a molecular mass of 30.4 kDa in SDS-polyacrylamide gel electrophoresis under both reducing and nonreducing conditions, indicating that it is a monomeric protein. Its N-terminal sequence was highly homologous to those of chitinases and chitinase precursors from plants. It exerted potent antifungal action toward a variety of fungal species, including Pythium aphanidermatum, Fusarium solani, Physalospora piricola, Alternaria alternata, Botrytis cinerea, and Fusarium oxysporum. In addition, this novel protein exhibited antiproliferative activity against tumor cells. These findings further the progress in the research of leguminous plants.

Protective effects of Castanopsis cuspidate through activation of ERK and NF-kappaB on oxidative cell death induced by hydrogen peroxide

The protective effect of Castanopsis cuspidate var. sieboldii was examined on H2O2-induced cell damage. The ethanol extract of Castanopsis cuspidate was found to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and reduce intracellular reactive oxygen species (ROS) generation, and thus prevent lipid peroxidation and cellular DNA damage induced by H2O2. As a result, Castanopsis extract reduced H2O2-induced cell death of V79-4 cells via inhibition of apoptosis. Castanopsis extract was also found to increase catalase activity and its protein expression. Further molecular mechanistic studies revealed that Castanopsis extract enhanced phosphorylation of extracellular signal regulated kinase (ERK) and activity of nuclear factor kappa B (NF-kappaB). Taken together, the results suggest that Castanopsis extract protects V79-4 cells against oxidative damage by enhancing catalase activity and modulating the ERK and NF-kappaB signal pathway.

An antifungal peptide from red lentil seeds

An antifungal peptide, with a molecular mass of 11 kDa, was isolated from dry seeds of the red lentil (Lens culinaris) using a procedure that involved four chromatographic steps. The antifungal peptide was unadsorbed on DEAE-cellulose, and adsorbed on Affi-gel blue gel and S-Sepharose. The final chromatographic step involved gel filtration by fast protein liquid chromatography on Superdex 75. The antifungal peptide inhibited mycelial growth in Mycosphaerella arachidicola with an IC50 of 36 microM. It also exhibited antifungal activity against Fusarium oxysporum, but there was no inhibitory activity toward tumor cell lines and human immunodeficiency virus type 1 reverse transcriptase (RT).

Isolation and characterization of an antifungal peptide with antiproliferative activity from seeds of Phaseolus vulgaris cv. ‘Spotted Bean’

A 7.3-kDa antifungal peptide with an N-terminal sequence exhibiting remarkable homology to defensins from other leguminous plants was isolated from Phaseolus vulgaris cv. 'Spotted Bean'. The isolation procedure involved ion exchange chromatography on O-diethylaminoethyl (DEAE) cellulose, affinity chromatography on Affi-gel blue gel, ion exchange chromatography on SP-Sepharose, and gel filtration by fast protein liquid chromatography on Superdex 75. The peptide was unadsorbed on DEAE-cellulose and adsorbed on Affi-gel blue gel and SP-Sepharose. It exerted an antifungal action on Fusarium oxysporum and Mycosphaerella arachidicola. It inhibited mycelial growth in F. oxysporum with an IC(50) value of 1.8 microM. It suppressed [methyl-(3)H]-thymidine incorporation by leukemia L1210 cells and MBL2 cells with an IC(50) value of 4.0 and 9.0 microM, respectively. There was no effect on HIV-1 reverse transcriptase activity when the peptide was tested up to 0.1 mM.

An antifungal protein from the pea Pisum sativum var. arvense Poir

An antifungal protein with a molecular mass of 11 kDa and a lysine-rich N-terminal sequence was isolated from the seeds of the pea Pisum sativum var. arvense Poir. The antifungal protein was unadsorbed on DEAE-cellulose but adsorbed on Affi-gel blue gel and CM-cellulose. It exerted antifungal activity against Physalospora piricola with an IC50 of 0.62 microM, and also antifungal activity against Fusarium oxysporum and Mycosphaerella arachidicola. It inhibited human immunodeficiency virus type 1 reverse transcriptase with an IC50 of 4.7 microM.

Phylogenetic and structural relationships of the PR5 gene family reveal an ancient multigene family conserved in plants and select animal taxa

Pathogenesis-related group 5 (PR5) plant proteins include thaumatin, osmotin, and related proteins, many of which have antimicrobial activity. The recent discovery of PR5-like (PR5-L) sequences in nematodes and insects raises questions about their evolutionary relationships. Using complete plant genome data and discovery of multiple insect PR5-L sequences, phylogenetic comparisons among plants and animals were performed. All PR5/PR5-L protein sequences were mined from genome data of a member of each of two main angiosperm groups-the eudicots (Arabidoposis thaliana) and the monocots (Oryza sativa)-and from the Caenorhabditis nematode (C. elegans and C. briggsase). Insect PR5-L sequences were mined from EST databases and GenBank submissions from four insect orders: Coleoptera (Diaprepes abbreviatus and Biphyllus lunatus), Orthoptera (Schistocerca gregaria), Hymenoptera (Lysiphlebus testaceipes), and Hemiptera (Toxoptera citricida). Parsimony and Bayesian phylogenetic analyses showed that the PR5 family is paraphyletic in plants, likely arising from 10 genes in a common ancestor to monocots and eudicots. After evolutionary divergence of monocots and eudicots, PR5 genes increased asymmetrically among the 10 clades. Insects and nematodes contain multiple sequences (seven PR5-Ls in nematodes and at least three in some insects) all related to the same plant clade, with nematode and insect sequences separating as two clades. Protein structural homology modeling showed strong similarity among animal and plant PR5/PR5-Ls, with divergence only in surface-exposed loops. Sequence and structural conservation among PR5/PR5-Ls suggests an important and conserved role throughout the evolutionary divergence of the diverse organisms from which they reside.

Naturally derived anti-HIV agents

The urgent need for new anti-HIV/AIDS drugs is a global concern. In addition to obvious economical and commercial hurdles, HIV/AIDS patients are faced with multifarious difficulties associated with the currently approved anti-HIV drugs. Adverse effects, the emergence of drug resistance and the narrow spectrum of activity have limited the therapeutic usefulness of the various reverse transcriptase and protease inhibitors that are currently available on the market. This has driven many scientists to look for new anti-retrovirals with better efficacy, safety and affordability. As has always been the case in the search for cures, natural sources offer great promise. Several natural products, mostly of plant origin have been shown to possess promising activities that could assist in the prevention and/or amelioration of the disease. Many of these anti-HIV agents have other medicinal values as well, which afford them further prospective as novel leads for the development of new drugs that can deal with both the virus and the various disorders that characterize HIV/AIDS. The aim of this review is to report new discoveries and updates pertaining to anti-HIV natural products. In the review anti-HIV agents have been classified according to their chemical classes rather than their target in the HIV replicative cycle, which is the most frequently encountered approach. Perusal of the literature revealed that most of these promising naturally derived anti-HIV compounds are flavonoids, coumarins, terpenoids, alkaloids, polyphenols, polysaccharides or proteins. It is our strong conviction that the results and experiences with many of the anti-HIV natural products will inspire and motivate even more researchers to look for new leads from plants and other natural sources.

Pleurostrin, an antifungal peptide from the oyster mushroom

A 7kDa peptide, with inhibitory activity on mycelial growth in the fungi Fusaerium oxysporum, Mycosphaerella arachidicola and Physalospora piricola, was isolated from fresh fruiting bodies of the oyster mushroom. The isolation procedure entailed extraction with an aqueous buffer, ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel blue gel and gel filtration by fast protein liquid chromatography on Superdex 75. The protein was unadsorbed on DEAE-cellulose and adsorbed on Affi-gel blue gel. It demonstrated an N-terminal sequence different from known antifungal proteins and peptides.

The transcription factor ATAF2 represses the expression of pathogenesis-related genes in Arabidopsis

ATAF2, a member of the plant-specific NAC-domain transcription factor family, is highly induced in leaves at a wound site and is responsive to the wound-related phytohormones methyl jasmonate and salicylic acid, but not to abscisic acid. Overexpression of ATAF2 leads to an increased biomass and yellowing of the leaves, but there is no obvious phenotype in two independent ATAF2 T-DNA insertion lines. At the transcriptome level, ATAF2 overexpression resulted in repression of a number of pathogenesis-related proteins. Conversely, four of these pathogenesis-related transcripts were increased in both ATAF2 knock-out lines. ATAF2 overexpressing plants showed a higher susceptibility to the soil-borne fungal pathogen Fusarium oxysporum. Our results indicate that ATAF2 functions as a repressor of pathogenesis-related proteins in Arabidopsis.

Isolation of trichogin, an antifungal protein from fresh fruiting bodies of the edible mushroom Tricholoma giganteum

An antifungal protein was isolated from the mushroom Tricholoma giganteum var. golden blessings. The protocol included ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel blue gel, ion exchange chromatography on CM-cellulose, and gel filtration by fast protein liquid chromatography on Superdex 75. The antifungal protein, designated trichogin, was unadsorbed on DEAE-cellulose but was adsorbed on Affi-gel blue gel and CM-cellulose. It exhibited antifungal activity against Fusarium oxysporum, Mycosphaerella arachidicola and Physalospora piricola. Trichogin inhibited HIV-1 reverse transcriptase with an IC50 of 83 nM.

Isolation of alliumin, a novel protein with antimicrobial and antiproliferative activities from multiple-cloved garlic bulbs

A protein designated alliumin, with a molecular mass of 13 kDa and an N-terminal sequence similar to a partial sequence of glucanase, and demonstrating antifungal activity against Mycosphaerella arachidicola, but not against Fusarium oxysporum, was isolated from multiple-cloved garlic (Allium sativum) bulbs. The protein, designated as alliumin, was purified using ion exchange chromatography on DEAE-cellulose, CM-cellulose and Mono S, affinity chromatography on Affi-gel blue gel, and gel filtration on Superdex 75. Alliumin was unadsorbed on DEAE-cellulose, but was adsorbed on Affi-gel blue gel, CM-cellulose and Mono S. Its antifungal activity was retained after boiling for 1 h and also after treatment with trypsin or chymotrypsin (1:1, w/w) for 30 min at room temperature. Alliumin was inhibitory to the bacterium Pseudomonas fluorescens and exerted antiproliferative activity toward leukemia L1210 cells. However, it was devoid of ribonuclease activity, protease activity, mitogenic activity toward mouse splenocytes, and antiproliferative activity toward hepatoma Hep G2 cells.

First report of a glutamine-rich antifungal peptide with immunomodulatory and antiproliferative activities from family Amaryllidaceae

This represents the first report of purification of a glutamine-rich antifungal peptide from family Amarylliaceace. The peptide, designated as nartazin, was purified from the bulbs of the Chinese daffodil Narcissus tazetta var. chinensis by means of ion-exchange chromatography and affinity chromatography. Its molecular mass was 7.1kDa, as determined by SDS-PAGE and gel filtration. Nartazin stimulated proliferation of mouse splenocytes and bone marrow cells but inhibited proliferation of leukemia L1210 cells. It also inhibited translation in a cell-free rabbit reticulocyte lysate system. The sequence of its first 20 N-terminal residues was characterized by an abundance of glutamine. The peptide possessed antifungal activity on four phytopathogenic fungi. Its activity was retained after incubation with bovine trypsin and chymotrypsin (enzyme: substrate ratio 1:10 w/w) at 37 degrees C for 1h but was attenuated after treatment with proteinase K. The data revealed its pronounced resistance to proteolytic digestion.

Antifungal proteins and peptides of leguminous and non-leguminous origins

Antifungal proteins and peptides, as their names imply, serve a protective function against fungal invasion. They are produced by a multitude of organisms including leguminous flowering plants, non-leguminous flowering plants, gymnosperms, fungi, bacteria, insects and mammals. The intent of the present review is to focus on the structural and functional characteristics of leguminous, as well as non-leguminous, antifungal proteins and peptides. A spectacular diversity of amino acid sequences has been reported. Some of the antifungal proteins and peptides are classified, based on their structures and/or functions, into groups including chitinases, glucanases, thaumatin-like proteins, thionins, and cyclophilin-like proteins. Some of the well-known proteins such as lectins, ribosome inactivating proteins, ribonucleases, deoxyribonucleases, peroxidases, and protease inhibitors exhibit antifungal activity. Different antifungal proteins may demonstrate different fungal specificities. The mechanisms of antifungal action of only some antifungal proteins including thaumatin-like proteins and chitinases have been elucidated.

Isolation and characterization of a 29-kDa glycoprotein with antifungal activity from bulbs of Urginea indica

In this study an antifungal protein from Urginea indica bulbs was purified to homogeneity by acid precipitation, Diol 300 Gel-filtration, and C(18) reverse phase HPLC. Its molecular mass was estimated to be 29 kDa and periodic acid-Schiff (PAS) staining showed that identified antifungal molecule is a glycoprotein. The neutralization of antifungal activity after periodate oxidation of 29 kDa glycoprotein suggests that the glycan part of the molecule appears to be involved in antifungal activity. N-terminal amino acid sequence of the purified protein was determined as SQLKAXIXDF. This sequence had no sequence similarity with any antifungal proteins. A polyclonal antiserum was raised against purified protein and used in immunolocalization analysis. Results suggest that it is localized to the cell wall of the bulb. Antifungal tests have demonstrated that U. indica protein exerts a fungistatic effect. It completely inhibits the germination of spores and hyphal growth of Fusarium oxysporum.