Toxins

2005 KiB

Open AccessArticle

Spatial Patterns of Aflatoxin Levels in Relation to Ear-Feeding Insect Damage in Pre-Harvest Corn

by Xinzhi Ni, Jeffrey P. Wilson, G. David Buntin, Baozhu Guo, Matthew D. Krakowsky, R. Dewey Lee, Ted E. Cottrell, Brian T. Scully, Alisa Huffaker and Eric A. Schmelz

Toxins 2011, 3(7), 920-931; https://doi.org/10.3390/toxins3070920 - 21 Jul 2011

Cited by 41 | Viewed by 8838

Abstract

Key impediments to increased corn yield and quality in the southeastern US coastal plain region are damage by ear-feeding insects and aflatoxin contamination caused by infection of Aspergillus flavus. Key ear-feeding insects are corn earworm, Helicoverpa zea, fall armyworm, Spodoptera frugiperda [...] Read more.

Key impediments to increased corn yield and quality in the southeastern US coastal plain region are damage by ear-feeding insects and aflatoxin contamination caused by infection of Aspergillus flavus. Key ear-feeding insects are corn earworm, Helicoverpa zea, fall armyworm, Spodoptera frugiperda, maize weevil, Sitophilus zeamais, and brown stink bug, Euschistus servus. In 2006 and 2007, aflatoxin contamination and insect damage were sampled before harvest in three 0.4-hectare corn fields using a grid sampling method. The feeding damage by each of ear/kernel-feeding insects (i.e., corn earworm/fall armyworm damage on the silk/cob, and discoloration of corn kernels by stink bugs), and maize weevil population were assessed at each grid point with five ears. The spatial distribution pattern of aflatoxin contamination was also assessed using the corn samples collected at each sampling point. Aflatoxin level was correlated to the number of maize weevils and stink bug-discolored kernels, but not closely correlated to either husk coverage or corn earworm damage. Contour maps of the maize weevil populations, stink bug-damaged kernels, and aflatoxin levels exhibited an aggregated distribution pattern with a strong edge effect on all three parameters. The separation of silk- and cob-feeding insects from kernel-feeding insects, as well as chewing (i.e., the corn earworm and maize weevil) and piercing-sucking insects (i.e., the stink bugs) and their damage in relation to aflatoxin accumulation is economically important. Both theoretic and applied ramifications of this study were discussed by proposing a hypothesis on the underlying mechanisms of the aggregated distribution patterns and strong edge effect of insect damage and aflatoxin contamination, and by discussing possible management tactics for aflatoxin reduction by proper management of kernel-feeding insects. Future directions on basic and applied research related to aflatoxin contamination are also discussed. Full article

(This article belongs to the Special Issue Aflatoxins 2011)

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Figure 1
Ecological interactions among insect pests and aflatoxin contamination in corn ears between flowering and harvest in the Southeastern Coastal Plain Region of the U.S. Full article ">Figure 2
The spatial distribution patterns (i.e., aggregated distribution and edge effect) of corn earworm (CEW) damage (A), the number of maize weevils (B), percentage of stink bug-damaged kernels (C), and aflatoxin levels (ppb) (D) in the corn field at pre-harvest in 2006. Aflatoxin levels (ppb) (D) were not to corn earworm damage (A) (r = 0.1, P = 0.37, n = 76), but positively correlated to the number of maize weevils (B) (r = 0.25, P = 0.03, n = 76), and the percentage of stink bug-damaged kernels (C) (r = 0.36, P = 0.001, n = 76). Full article ">Figure 3
The spatial patterns (i.e., aggregated distribution, and edge effect) of the number of maize weevils in the corn fields on the three research farms at preharvest in 2007. (A) Belflower Farm, (B) Gibbs Farm, and (C) Lang Farm. The grid size was the same in all three fields, although the grid size was smaller in the graph. Full article ">Figure 4
The spatial patterns (i.e., aggregated distribution, and edge effect) of the stink bug-discolored kernels (%) in the corn fields on the three research farms at preharvest in 2007. in the corn fields on the three farms in 2007; (A) Belflower Farm, (B) Gibbs Farm, and (C) Lang Farm. The grid size was the same in all three fields, although the grid size was smaller in the graph. Full article ">Figure 5
The spatial patterns (i.e., aggregated distribution, and edge effect) of the aflatoxin contamination (ppb) in the corn samples on the three research farms at preharvest in 2007. (A) Belflower Farm, (B) Gibbs Farm, and (C) Lang Farm. The grid size was the same in all three fields, although the grid size was smaller in the graph. Full article ">

394 KiB

Open AccessArticle

Protein-Bound Uremic Toxins: New Insight from Clinical Studies

by Sophie Liabeuf, Tilman B. Drüeke and Ziad A. Massy

Toxins 2011, 3(7), 911-919; https://doi.org/10.3390/toxins3070911 - 20 Jul 2011

Cited by 100 | Viewed by 10302

Abstract

The uremic syndrome is attributed to the progressive retention of a large number of compounds which, under normal conditions, are excreted by healthy kidneys. The compounds are called uremic toxins when they interact negatively with biological functions. The present review focuses on a [...] Read more.

The uremic syndrome is attributed to the progressive retention of a large number of compounds which, under normal conditions, are excreted by healthy kidneys. The compounds are called uremic toxins when they interact negatively with biological functions. The present review focuses on a specific class of molecules, namely the family of protein-bound uremic toxins. Recent experimental studies have shown that protein-bound toxins are involved not only in the progression of chronic kidney disease (CKD), but also in the generation and aggravation of cardiovascular disease. Two protein-bound uremic retention solutes, namely indoxyl sulfate and p-cresyl sulfate, have been shown to play a prominent role. However, although these two molecules belong to the same class of molecules, exert toxic effects on the cardiovascular system in experimental animals, and accumulate in the serum of patients with CKD they may have different clinical impacts in terms of cardiovascular disease and other complications. The principal aim of this review is to evaluate the effect of p-cresyl sulfate and indoxyl sulfate retention on CKD patient outcomes, based on recent clinical studies. Full article

(This article belongs to the Special Issue Uremic Toxins)

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420 KiB

Open AccessArticle

Isolation and Biochemical Characterization of Rubelase, a Non-Hemorrhagic Elastase from Crotalus ruber ruber (Red Rattlesnake) Venom

by Yumiko Komori, Kaname Sakai, Katsuyoshi Masuda and Toshiaki Nikai

Toxins 2011, 3(7), 900-910; https://doi.org/10.3390/toxins3070900 - 19 Jul 2011

Cited by 9 | Viewed by 6315

Abstract

A novel non-hemorrhagic basic metalloprotease, rubelase, was isolated from the venom of Crotalus ruber ruber. Rubelase hydrolyzes succinyl-L-alanyl-L-alanyl-L-alanyl p-nitroanilide (STANA), a specific substrate for elastase, and the hydrolytic activity was inhibited by chelating agents. It also hydrolyzes collagen and fibrinogen. However, [...] Read more.

A novel non-hemorrhagic basic metalloprotease, rubelase, was isolated from the venom of Crotalus ruber ruber. Rubelase hydrolyzes succinyl-L-alanyl-L-alanyl-L-alanyl p-nitroanilide (STANA), a specific substrate for elastase, and the hydrolytic activity was inhibited by chelating agents. It also hydrolyzes collagen and fibrinogen. However, hemorrhagic activity was not observed. By ESI/Q-TOF and MALDI/TOF mass spectrometry combined with Edman sequencing procedure, the molecular mass of rubelase was determined to be 23,266 Da. Although its primary structure was similar to rubelysin (HT-2), a hemorrhagic metalloprotease isolated from the same snake venom, the circumstances surrounding putative zinc binding domain HEXXHXXGXXH were found to be different when the three-dimensional computer models of both metalloproteases were compared. The cytotoxic effects of rubelase and rubelysin on cultured endothelial and smooth muscle cells were also different, indicating that the substitution of several amino acid residues causes the changes of active-site conformation and cell preference. Full article

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Isolation of rubelase from Crotalus r. ruber venom by chromatography. (A) HW-50 gel filtration. Crotalus r. ruber crude venom (69 mg) was applied to a column (1.5 × 100 cm) equilibrated with 0.01 M Tris-HCl buffer (pH 7.2) containing 0.01 M NaCl. Fractions of 3.0 mL were collected at a flow rate of 10.8 mL/h; (B) CM-cellulose column chromatography. The enzyme (fraction 6) was applied to a column (1.5 × 45 cm) equilibrated with the same buffer, and eluted with a linear gradient from 0.01 to 0.5 M NaCl. Full article ">Figure 2
ESI/Q-TOF mass spectra of rubelase from Crotalus r. ruber venom. SDS-polyacrylamide gel electrophoresis (insert). Full article ">Figure 3
Comparison of the amino acid sequence of rubelase with several low molecular weight metalloproteinases from snake venoms. <E denotes L-pyroglutamic acid. The putative zinc binding ligand and the catalytic domain are indicated by ▲. Full article ">Figure 4
Cytotoxic effects of rubelase and rubelysin on cultured cells. (A) HUVEC: human umbilical vein endothelial cells; (B) HPAEC: human pulmonary artery endothelial cells; (C) HASMC: human aortic smooth muscle cells. Rubelase and rubelysin were added to the cells at various concentrations. After incubation for 18 h, viable cells were counted using the colorimetric method. The results shown represent the average of five experiments. The absorbance of cultured cells incubated with saline or crude venom (10 µg) was defined as control and (cytotoxic) positive control *, respectively. Full article ">Figure 5
Fluorescence micrographs of HPAEC (×60) after incubation with rubelase and rubelysin. Control cells (A); and the cells incubated with rubelase (B); and rubelysin (C). Full article ">Figure 6
Molecular models of rubelase and rubelysin with the zinc binding site and substituted amino acid residues (A); and views of the surrounding structure of the zinc binding site (B). Full article ">

425 KiB

Open AccessArticle

G_i/o Protein-Dependent and -Independent Actions of Pertussis Toxin (PTX)

by Supachoke Mangmool and Hitoshi Kurose

Toxins 2011, 3(7), 884-899; https://doi.org/10.3390/toxins3070884 - 15 Jul 2011

Cited by 151 | Viewed by 31774

Abstract

Pertussis toxin (PTX) is a typical A-B toxin. The A-protomer (S1 subunit) exhibits ADP-ribosyltransferase activity. The B-oligomer consists of four subunits (S2 to S5) and binds extracellular molecules that allow the toxin to enter the cells. The A-protomer ADP-ribosylates the α subunits of [...] Read more.

Pertussis toxin (PTX) is a typical A-B toxin. The A-protomer (S1 subunit) exhibits ADP-ribosyltransferase activity. The B-oligomer consists of four subunits (S2 to S5) and binds extracellular molecules that allow the toxin to enter the cells. The A-protomer ADP-ribosylates the α subunits of heterotrimeric G_i/o proteins, resulting in the receptors being uncoupled from the G_i/o proteins. The B-oligomer binds proteins expressed on the cell surface, such as Toll-like receptor 4, and activates an intracellular signal transduction cascade. Thus, PTX modifies cellular responses by at least two different signaling pathways; ADP-ribosylation of the Gα_i/o proteins by the A-protomer (G_i/o protein-dependent action) and the interaction of the B-oligomer with cell surface proteins (G_i/o protein-independent action). Full article

(This article belongs to the Special Issue Novel Properties of Well-Characterized Toxins)

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Figure 1
Pertussis toxin (PTX) structural organization. PTX contains five different subunits that are arranged in a typical A-B structure. The A-protomer contains an enzymatically active S1 subunit that is on the top of B-oligomer. The B-oligomer is composed of two dimers, S2-S4 and S3-S4 dimers, which are held together by the S5 subunit. Full article ">Figure 2
Schematic diagram of the ADP-ribosylation of α subunit of heterotrimeric Gi/o protein by pertussis toxin (PTX). PTX catalyzes the cleavage of the C-N bond between a carbon atom of ribose and a nitrogen atom of nicotinamide, and transfers the ADP-ribosyl moiety to an acceptor molecule. Full article ">Figure 3
Uncoupling of Gαi/o proteins from their cognate G protein-coupled receptor (GPCR). Activation of GPCRs leads to dissociation of heterotrimeric G protein complex into Gαi/o and βγ subunit. The exchange of GTP from GDP results in activation of the inhibitory G protein (Gαi/o), thereby inhibiting adenylyl cyclase (AC) activity. When the A-protomer of PTX penetrates into the host cells, the Gαi/o is ADP-ribosylated at cysteine residue resulting in inactivation of Gαi/o. The inhibitory effect of Gαi/o on AC activity results in the elevation of intracellular cAMP levels, leading to activation of the cAMP-mediated signaling pathway. This enhanced pathway by PTX is recognized as the Gi/o protein-dependent pathway. Full article ">Figure 4
Gi/o protein-dependent and -independent effects of PTX. Following the binding of PTX to host cells, the A-protomer penetrates through the cell membrane. A-protomer is dissociated from B-oligomer and released into the cytoplasm. A-protomer then catalyzes the ADP-ribosylation of Gαi/o that leads to uncoupling of Gαi/o from its cognate inhibitory GPCRs. The inhibitory effect of Gαi/o on AC activity is then halted, resulting in accumulation of cAMP. This action of PTX results in disruption of cellular function through cAMP-mediated signaling pathway (Gi/o protein-dependent effects). In a separate pathway, the B-oligomer binds to and interacts with several targeted proteins on the plasma membrane, leading to the induction of the biological responses that are independent of ADP-ribosylation of Gαi/o protein (Gi/o protein-independent effects). Full article ">

2024 KiB

Open AccessReview

Immunotoxins and Anticancer Drug Conjugate Assemblies: The Role of the Linkage between Components

by Franco Dosio, Paola Brusa and Luigi Cattel

Toxins 2011, 3(7), 848-883; https://doi.org/10.3390/toxins3070848 - 14 Jul 2011

Cited by 148 | Viewed by 17933

Abstract

Immunotoxins and antibody-drug conjugates are protein-based drugs combining a target-specific binding domain with a cytotoxic domain. Such compounds are potentially therapeutic against diseases including cancer, and several clinical trials have shown encouraging results. Although the targeted elimination of malignant cells is an elegant [...] Read more.

Immunotoxins and antibody-drug conjugates are protein-based drugs combining a target-specific binding domain with a cytotoxic domain. Such compounds are potentially therapeutic against diseases including cancer, and several clinical trials have shown encouraging results. Although the targeted elimination of malignant cells is an elegant concept, there are numerous practical challenges that limit conjugates’ therapeutic use, including inefficient cellular uptake, low cytotoxicity, and off-target effects. During the preparation of immunoconjugates by chemical synthesis, the choice of the hinge component joining the two building blocks is of paramount importance: the conjugate must remain stable in vivo but must afford efficient release of the toxic moiety when the target is reached. Vast efforts have been made, and the present article reviews strategies employed in developing immunoconjugates, focusing on the evolution of chemical linkers. Full article

(This article belongs to the Special Issue Immunotoxins)

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708 KiB

Open AccessArticle

Adapting Yeast as Model to Study Ricin Toxin A Uptake and Trafficking

by Björn Becker and Manfred J. Schmitt

Toxins 2011, 3(7), 834-847; https://doi.org/10.3390/toxins3070834 - 5 Jul 2011

Cited by 6 | Viewed by 8576

Abstract

The plant A/B toxin ricin represents a heterodimeric glycoprotein belonging to the family of ribosome inactivating proteins, RIPs. Its toxicity towards eukaryotic cells results from the depurination of 28S rRNA due to the N-glycosidic activity of ricin toxin A chain, RTA. Since [...] Read more.

The plant A/B toxin ricin represents a heterodimeric glycoprotein belonging to the family of ribosome inactivating proteins, RIPs. Its toxicity towards eukaryotic cells results from the depurination of 28S rRNA due to the N-glycosidic activity of ricin toxin A chain, RTA. Since the extention of RTA by a mammalian-specific endoplasmic reticulum (ER) retention signal (KDEL) significantly increases RTA in vivo toxicity against mammalian cells, we here analyzed the phenotypic effect of RTA carrying the yeast-specific ER retention motif HDEL. Interestingly, such a toxin (RTA^HDEL) showed a similar cytotoxic effect on yeast as a corresponding RTA^KDEL variant on HeLa cells. Furthermore, we established a powerful yeast bioassay for RTA in vivo uptake and trafficking which is based on the measurement of dissolved oxygen in toxin-treated spheroplast cultures of S. cerevisiae. We show that yeast spheroplasts are highly sensitive against external applied RTA and further demonstrate that its toxicity is greatly enhanced by replacing the C-terminal KDEL motif by HDEL. Based on the RTA resistant phenotype seen in yeast knock-out mutants defective in early steps of endocytosis (∆end3) and/or in RTA depurination activity on 28S rRNA (∆rpl12B) we feel that the yeast-based bioassay described in this study is a powerful tool to dissect intracellular A/B toxin transport from the plasma membrane through the endosomal compartment to the ER. Full article

(This article belongs to the Special Issue Ricin Toxin)

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Figure 1
(A) Schematic outline of ricin toxin A (RTA) variants used in this study.In each fusion protein, the type of endoplasmic reticulum (ER) retention signal fused to RTA (K/HDEL) and the total size (in bp) is indicated. Length of the (His)6-tag and the mammalian- or yeast-specific ER retention motifs are also shown. RTA fusions were cloned into pET24a(+) and expressed in E. coli; (B) RTA purification by Ni2+-NTA chromatography.Purified samples (15‑25 µg) were analyzed by SDS‑PAGE and Coomassie staining. Lane 1: PAGE Ruler prestained (Fermentas); Lane 2: unmodified RTA; Lane 3: RTAHDEL; Lane 4: RTAKDEL. Full article ">Figure 2
RTA containing a mammalian- or yeast-specific ER retention signal is toxic to HeLa cells. (A) XTT based cell viability assay of HeLa cells. Cells were incubated in the presence of 12 µg of the indicated RTA variant and controls for 48h (buffer control set to 100%). Each experiment was performed in triplicate (n = 3) and standard deviation (red bar) and p-values (*p< 0.05) are indicated; (B) Trypan blue staining of HeLa cells treated with 12 µg of each toxin variant after an incubation of 24 (black) or 48 (white) hours. Schemata show HeLa cell viability in % and the standard deviation for each sample (red bar). Each measurement was performed twice (n = 2). For p‑value calculation, RTA-treated samples were compared to the negative control (*p < 0.05; **p < 0.01); (C) Phase contrast microscopy of RTA treated HeLa cells after 48 h (10,000 magnification). Cells were incubated in the presence of 12 µg of the indicated RTA protein fusion. Full article ">Figure 3
RTA toxicity against yeast spheroplasts. Dissolved oxygen concentration was measured for intact wild-type cells (WT) and spheroplasts in the presence of the indicated RTA variant. All experiments were performed in triplicate (n = 3) at 30 °C and 120 rpm over 16 h. (A) Intact wild-type yeast cells treated with 50 µg of the indicated RTA variant; (B,C) Same experiment performed on yeast spheroplasts in the presence of 50 or 3 µg RTA; (D) Spheroplasts treated with 50 µg RTA before and after heat-inactivation; (E,F) Yeast spheroplasts of a Δrpl12B or Δend3 mutant in the presence of 50 µg of the indicated RTA variant. Full article ">Figure 4
PI fluorescence of RTA-treated intact cells and yeast spheroplasts. Propidium iodide (PI) fluorescence intensity of yeast spheroplasts and intact cells after treatment with the indicated RTA variant. In the positive control (set to 100%), cells were heat-inactivated at 95 °C for 20 min. In each case, cells were incubated in the presence of 12 µg of the indicated RTA variant for 24 h (mean average of five independent experiments; standard deviation (red bar) and p-values (*p< 0.05, **p< 0.01) are indicated). Full article ">

640 KiB

Open AccessArticle

Comparative ¹H NMR Metabolomic Urinalysis of People Diagnosed with Balkan Endemic Nephropathy, and Healthy Subjects, in Romania and Bulgaria: A Pilot Study

by Peter Mantle, Mirela Modalca, Andrew Nicholls, Calin Tatu, Diana Tatu and Draga Toncheva

Toxins 2011, 3(7), 815-833; https://doi.org/10.3390/toxins3070815 - 4 Jul 2011

Cited by 13 | Viewed by 7698

Abstract

¹H NMR spectroscopy of urine has been applied to exploring metabolomic differences between people diagnosed with Balkan endemic nephropathy (BEN), and treated by haemodialysis, and those without overt renal disease in Romania and Bulgaria. Convenience sampling was made from patients receiving haemodialysis [...] Read more.

¹H NMR spectroscopy of urine has been applied to exploring metabolomic differences between people diagnosed with Balkan endemic nephropathy (BEN), and treated by haemodialysis, and those without overt renal disease in Romania and Bulgaria. Convenience sampling was made from patients receiving haemodialysis in hospital and healthy controls in their village. Principal component analysis clustered healthy controls from both countries together. Bulgarian BEN patients clustered separately from controls, though in the same space. However, Romanian BEN patients not only also clustered away from controls but also clustered separately from the BEN patients in Bulgaria. Notably, the urinary metabolomic data of two people sampled as Romanian controls clustered within the Romanian BEN group. One of these had been suspected of incipient symptoms of BEN at the time of selection as a ‘healthy’ control. This implies, at first sight, that metabolomic analysis can be predictive of impending morbidity before conventional criteria can diagnose BEN. Separate clustering of BEN patients from Romania and Bulgaria could indicate difference in aetiology of this particular silent renal atrophy in different geographic foci across the Balkans. Full article

(This article belongs to the Special Issue Uremic Toxins)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
Comparisons of urinary creatinine concentrations in sample groups sourced in Bulgaria and Romania showing dominance of lower values for people diagnosed with BEN. Illustration of Bulgarian data omitted one exceptionally high value (42.5 mmol/L) for a control subject, which otherwise distorts the graphical format. The three lowest values for the Romanian controls were from subjects who had recently been drinking. Full article ">Figure 2
PLS-DA scores plot of the urinary data from Romanian and Bulgarian BEN patients, familial/regional control subjects and subjects with other forms of kidney disease. Full article ">Figure 3
Scores plot of the first two components showing the separation of the samples from the Romanian BEN subjects compared to all other groups. Full article ">Figure 4
Scores plot of the second and third components with the Romanian BEN samples removed from the visualisation showing the clustering each of the other groups. Full article ">Figure 5
Scene at rear of house of former BEN patient in Erghevita, Romania showing re-growth of the dominant weed Aristolochia clematitis. May 2004. Full article ">

165 KiB

Open AccessReview

Trichothecenes: From Simple to Complex Mycotoxins

by Susan P. McCormick, April M. Stanley, Nicholas A. Stover and Nancy J. Alexander

Toxins 2011, 3(7), 802-814; https://doi.org/10.3390/toxins3070802 - 1 Jul 2011

Cited by 397 | Viewed by 25437

Abstract

As the world’s population grows, access to a safe food supply will continue to be a global priority. In recent years, the world has experienced an increase in mycotoxin contamination of grains due to climatic and agronomic changes that encourage fungal growth during [...] Read more.

As the world’s population grows, access to a safe food supply will continue to be a global priority. In recent years, the world has experienced an increase in mycotoxin contamination of grains due to climatic and agronomic changes that encourage fungal growth during cultivation. A number of the molds that are plant pathogens produce trichothecene mycotoxins, which are known to cause serious human and animal toxicoses. This review covers the types of trichothecenes, their complexity, and proposed biosynthetic pathways of trichothecenes. Full article

(This article belongs to the Special Issue Trichothecenes)

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414 KiB

Open AccessArticle

Ricin Trafficking in Plant and Mammalian Cells

by J. Michael Lord and Robert A. Spooner

Toxins 2011, 3(7), 787-801; https://doi.org/10.3390/toxins3070787 - 30 Jun 2011

Cited by 63 | Viewed by 10084

Abstract

Ricin is a heterodimeric plant protein that is potently toxic to mammalian and many other eukaryotic cells. It is synthesized and stored in the endosperm cells of maturing Ricinus communis seeds (castor beans). The ricin family has two major members, both, lectins, collectively [...] Read more.

Ricin is a heterodimeric plant protein that is potently toxic to mammalian and many other eukaryotic cells. It is synthesized and stored in the endosperm cells of maturing Ricinus communis seeds (castor beans). The ricin family has two major members, both, lectins, collectively known as Ricinus communis agglutinin ll (ricin) and Ricinus communis agglutinin l (RCA). These proteins are stored in vacuoles within the endosperm cells of mature Ricinus seeds and they are rapidly broken down by hydrolysis during the early stages of post-germinative growth. Both ricin and RCA traffic within the plant cell from their site of synthesis to the storage vacuoles, and when they intoxicate mammalian cells they traffic from outside the cell to their site of action. In this review we will consider both of these trafficking routes. Full article

(This article belongs to the Special Issue Ricin Toxin)

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398 KiB

Open AccessArticle

Transcriptional Profiles Uncover Aspergillus flavus-Induced Resistance in Maize Kernels

by Meng Luo, Robert L. Brown, Zhi-Yuan Chen, Abebe Menkir, Jiujiang Yu and Deepak Bhatnagar

Toxins 2011, 3(7), 766-786; https://doi.org/10.3390/toxins3070766 - 29 Jun 2011

Cited by 29 | Viewed by 7751

Abstract

Aflatoxin contamination caused by the opportunistic pathogen A. flavus is a major concern in maize production prior to harvest and through storage. Previous studies have highlighted the constitutive production of proteins involved in maize kernel resistance against A. flavus’ infection. However, little [...] Read more.

Aflatoxin contamination caused by the opportunistic pathogen A. flavus is a major concern in maize production prior to harvest and through storage. Previous studies have highlighted the constitutive production of proteins involved in maize kernel resistance against A. flavus’ infection. However, little is known about induced resistance nor about defense gene expression and regulation in kernels. In this study, maize oligonucleotide arrays and a pair of closely-related maize lines varying in aflatoxin accumulation were used to reveal the gene expression network in imbibed mature kernels in response to A. flavus’ challenge. Inoculated kernels were incubated 72 h via the laboratory-based Kernel Screening Assay (KSA), which highlights kernel responses to fungal challenge. Gene expression profiling detected 6955 genes in resistant and 6565 genes in susceptible controls; 214 genes induced in resistant and 2159 genes induced in susceptible inoculated kernels. Defense related and regulation related genes were identified in both treatments. Comparisons between the resistant and susceptible lines indicate differences in the gene expression network which may enhance our understanding of the maize-A. flavus interaction. Full article

(This article belongs to the Special Issue Aflatoxins 2011)

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Functional categories of differentially expressed genes in the comparison of noninoculated Eyl25(R) with noninoculated Eyl31(S). 1 biological process unknown; 2 catabolism; 3 cell fate and development; 4 metabolism; 5 protein bio-synthesis; 6 protein fate; 7 response to stress; 8 signal transduction; 9 transcription; 10 transport. Full article ">Figure 2
Survey of differentially expressed genes in A. flavus inoculated Eyl25(R) and Eyl31(S) kernels after 72 h incubation. Full article ">Figure 3
Proportion of differentially expressed genes among functional categories in the comparison among A. flavus challenged Eyl25(R), Eyl31(S), and noninoculated controls. 1 biological process unknown; 2 catabolism; 3 cell fate and development; 4 metabolism; 5 protein biosynthesis; 6 protein fate; 7 response to stress; 8 signal trans-duction; 9 transcription; 10 transport. T = inoculated; C = noninoculated. Full article ">Figure 4
Proportion of differentially expressed genes among functional categories in the comparison of inoculated Eyl25(R) with inoculated Eyl31(S). 1 biological process unknown; 2 catabolism; 3 cell fate and development; 4 metabolism; 5 protein biosynthesis; 6 protein fate; 7 response to stress; 8 signal transduction; 9 transcription; 10 transport. Full article ">Figure 5
Venn diagram analysis for defense related genes for A. flavus-inoculated experiments involving Eyl25(R) and Eyl31(S). Full article ">

409 KiB

Open AccessArticle

A Public Platform for the Verification of the Phenotypic Effect of Candidate Genes for Resistance to Aflatoxin Accumulation and Aspergillus flavus Infection in Maize

by Marilyn L. Warburton, William Paul Williams, Leigh Hawkins, Susan Bridges, Cathy Gresham, Jonathan Harper, Seval Ozkan, J. Erik Mylroie and Xueyan Shan

Toxins 2011, 3(7), 754-765; https://doi.org/10.3390/toxins3070754 - 24 Jun 2011

Cited by 9 | Viewed by 7806

Abstract

A public candidate gene testing pipeline for resistance to aflatoxin accumulation or Aspergillus flavus infection in maize is presented here. The pipeline consists of steps for identifying, testing, and verifying the association of selected maize gene sequences with resistance under field conditions. Resources [...] Read more.

A public candidate gene testing pipeline for resistance to aflatoxin accumulation or Aspergillus flavus infection in maize is presented here. The pipeline consists of steps for identifying, testing, and verifying the association of selected maize gene sequences with resistance under field conditions. Resources include a database of genetic and protein sequences associated with the reduction in aflatoxin contamination from previous studies; eight diverse inbred maize lines for polymorphism identification within any maize gene sequence; four Quantitative Trait Loci (QTL) mapping populations and one association mapping panel, all phenotyped for aflatoxin accumulation resistance and associated phenotypes; and capacity for Insertion/Deletion (InDel) and SNP genotyping in the population(s) for mapping. To date, ten genes have been identified as possible candidate genes and put through the candidate gene testing pipeline, and results are presented here to demonstrate the utility of the pipeline. Full article

(This article belongs to the Special Issue Aflatoxins 2011)

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Diagram of the steps in the candidate gene testing pipeline. Researchers interested in submitting gene sequences to be analyzed in the pipeline can contact the corresponding author of this article at the USDA/ARS Corn Host Plant Resistance Research Unit. Full article ">Figure 2
Example of an alignment of the 8 diverse inbred lines and the B73 reference (published genotype) used to find polymorphisms within one amplicon of the p450 candidate gene, and compared to the published reference B73 genome sequence. Boxes identify possible SNP or InDel polymorphisms between the lines that could be tested in the QTL and association mapping populations. Full article ">Figure 3
Example of genotyping available for polymorphisms to be tested in the QTL mapping population. The markers shown here segregate in the expected 1:2:1 pattern for F2 individuals. (A) SNP genotyping showing the genotype of the parents (well A1 and B1), F1 (well A2), and no-template control (well H12, the black spot), as well as four ambiguous (and thus missing) data points (in pink); (B) InDel genotyping showing the parents (two lanes following the molecular weight standard on the top tier of the InDel gel image, as read left to right) and F1 (third lane). Full article ">Figure 4
Examples of linkage maps generated in the F2:3 segregating population Mp715 × T173, showing the location of the gene based markers 1-Cys peroxiredoxin PER1 (PER) and Cytochrome P450 (P450), and previously mapped SSR markers. Both markers map to the expected location based on the location found by BLAST against these sequences in the B73 reference genome. The numbers to the left of the chromosomes are the cM distances calculated between markers by the JoinMap linkage mapping program. Full article ">Figure 5
Phenotypic effect of the SNP marker 262-1 identified within gene TC230106, in three environments (mean aflatoxin levels measured at MSU in 2000, 2001, and 2002) in the mapping population Mp313E × B73, as calculated by QTL cartographer. Full article ">

392 KiB

Open AccessArticle

Gene Expression Profiling and Identification of Resistance Genes to Aspergillus flavus Infection in Peanut through EST and Microarray Strategies

by Baozhu Guo, Natalie D. Fedorova, Xiaoping Chen, Chun-Hua Wan, Wei Wang, William C. Nierman, Deepak Bhatnagar and Jiujiang Yu

Toxins 2011, 3(7), 737-753; https://doi.org/10.3390/toxins3070737 - 24 Jun 2011

Cited by 59 | Viewed by 10787

Abstract

Aspergillus flavus and A. parasiticus infect peanut seeds and produce aflatoxins, which are associated with various diseases in domestic animals and humans throughout the world. The most cost-effective strategy to minimize aflatoxin contamination involves the development of peanut cultivars that are resistant to [...] Read more.

Aspergillus flavus and A. parasiticus infect peanut seeds and produce aflatoxins, which are associated with various diseases in domestic animals and humans throughout the world. The most cost-effective strategy to minimize aflatoxin contamination involves the development of peanut cultivars that are resistant to fungal infection and/or aflatoxin production. To identify peanut Aspergillus-interactive and peanut Aspergillus-resistance genes, we carried out a large scale peanut Expressed Sequence Tag (EST) project which we used to construct a peanut glass slide oligonucleotide microarray. The fabricated microarray represents over 40% of the protein coding genes in the peanut genome. For expression profiling, resistant and susceptible peanut cultivars were infected with a mixture of Aspergillus flavus and parasiticus spores. The subsequent microarray analysis identified 62 genes in resistant cultivars that were up-expressed in response to Aspergillus infection. In addition, we identified 22 putative Aspergillus-resistance genes that were constitutively up-expressed in the resistant cultivar in comparison to the susceptible cultivar. Some of these genes were homologous to peanut, corn, and soybean genes that were previously shown to confer resistance to fungal infection. This study is a first step towards a comprehensive genome-scale platform for developing Aspergillus-resistant peanut cultivars through targeted marker-assisted breeding and genetic engineering. Full article

(This article belongs to the Special Issue Aflatoxins 2011)

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Toxins, Volume 3, Issue 7 (July 2011) – 12 articles , Pages 737-931

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