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Sweany RR, Cary JW, Jaynes JM, Rajasekaran K. Broad-Spectrum Antimicrobial Activity of Synthetic Peptides GV185 and GV187. PLANT DISEASE 2023; 107:3211-3221. [PMID: 36947838 DOI: 10.1094/pdis-11-22-2572-re] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Optimizing synthetic antimicrobial peptides for safe and enhanced activity against fungal and bacterial pathogens is useful for genetic engineering of plants for resistance to plant pathogens and their associated mycotoxins. Nine synthetic peptides modeled after lytic peptides tachyplesin 1, D4E1 from cecropin A, and protegrin 1 were added to germinated spores of fungal species Aspergillus flavus, Rhizopus stolonifer, Fusarium oxysporum f. sp. vasinfectum, F. verticillioides, F. graminearum, Claviceps purpurea, Verticillium dahliae, and Thielaviopsis basicola and bacterial cultures of Pseudomonas syringae pv. tabaci and Xanthomonas campestris pv. campestris at different doses and inhibitory dose response curves, and were modeled to assess antimicrobial activity. Peptides GV185 and GV187, modified from tachyplesin 1, had superior abilities to inhibit fungal and bacterial growth (50% inhibitory concentrations [IC50] ranging from 0.1 to 8.7 µM). R. stolonifer (IC50 = 8.1 µM), A. flavus (IC50 = 3.1 µM), and F. graminearum (IC50 = 2.2 µM) were less inhibited by GV185 and GV187 than all the remaining fungi (IC50 = 1.4 µM) and bacteria (IC50 = 0.1 µM). Of the remaining peptides, GV193, GV195, and GV196 (IC50 range of 0.9 to 6.6 µM) inhibited fungal growth of A. flavus, F. verticillioides, and F. graminearum less than GV185 and GV187 (IC50 range of 0.8 to 3.9 µM), followed by GV197 (IC50 range of 0.8 to 9.1 µM), whereas GV190 and GV192 inhibited poorly (IC50 range of 28.2 to 36.6 µM and 15.5 to 19.4 µM, respectively) and GV198 stimulated growth. GV185 and GV187 had slightly weaker hydrophobic and cationic residues than other tachyplesin 1 modified peptides but still had unexpectedly high lytic activity. Germinated fungal spores of R. stolonifer and F. graminearum exposed to these two peptides and D4E1 and AGM182 appeared wrinkled, with perforations near potential cytoplasmic leakage, which provided evidence of plasma membrane and cell wall lysis. We conclude that peptides GV185 and GV187 are promising candidates for genetic engineering of crops for resistance to plant-pathogenic bacteria and fungi, including A. flavus and aflatoxin contamination.
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Affiliation(s)
- Rebecca R Sweany
- Food and Feed Safety Research Unit, Southern Regional Research Center, United States Department of Agriculture-Agricultural Research Service, New Orleans, LA 70124
| | - Jeffrey W Cary
- Food and Feed Safety Research Unit, Southern Regional Research Center, United States Department of Agriculture-Agricultural Research Service, New Orleans, LA 70124
| | - Jesse M Jaynes
- Genvor, LLC, Dallas, TX 75240
- College of Agriculture, Environment and Nutrition Sciences, and College of Arts and Sciences, Tuskegee University, Tuskegee, AL 36088
| | - Kanniah Rajasekaran
- Food and Feed Safety Research Unit, Southern Regional Research Center, United States Department of Agriculture-Agricultural Research Service, New Orleans, LA 70124
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Abstract
Plant disease control requires novel approaches to mitigate the spread of and losses caused by current, emerging, and re-emerging diseases and to adapt plant protection to global climate change and the restrictions on the use of conventional pesticides. Currently, disease management relies mainly on biopesticides, which are required for the sustainable use of plant-protection products. Functional peptides are candidate biopesticides because they originate from living organisms or are synthetic analogs and provide novel mechanisms of action against plant pathogens. Hundreds of compounds exist that cover an extensive range of activities against viruses, bacteria and phytoplasmas, fungi and oomycetes, and nematodes. Natural sources, chemical synthesis, and biotechnological platforms may provide peptides at large scale for the industry and growers. The main challenges for their use in plant disease protection are (a) the requirement of stability in the plant environment and counteracting resistance in pathogen populations, (b) the need to develop suitable formulations to increase their shelf life and methods of application, (c) the selection of compounds with acceptable toxicological profiles, and (d) the high cost of production for agricultural purposes. In the near future, it is expected that several functional peptides will be commercially available for plant disease control, but more effort is needed to validate their efficacy at the field level and fulfill the requirements of the regulatory framework.
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Affiliation(s)
- Emilio Montesinos
- Institute of Food and Agricultural Technology, Plant Pathology-CIDSAV, University of Girona, Girona, Spain;
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3
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Heterologous expression of antimicrobial peptides S-thanatin and bovine lactoferricin in the marine diatom Phaeodactylum tricornutum enhances native antimicrobial activity against Gram-negative bacteria. ALGAL RES 2022. [DOI: 10.1016/j.algal.2022.102927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Dash R, Bhattacharjya S. Thanatin: An Emerging Host Defense Antimicrobial Peptide with Multiple Modes of Action. Int J Mol Sci 2021; 22:ijms22041522. [PMID: 33546369 PMCID: PMC7913509 DOI: 10.3390/ijms22041522] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 01/28/2021] [Accepted: 02/01/2021] [Indexed: 12/11/2022] Open
Abstract
Antimicrobial peptides (AMPs) possess great potential for combating drug-resistant bacteria. Thanatin is a pathogen-inducible single-disulfide-bond-containing β-hairpin AMP which was first isolated from the insect Podisus maculiventris. The 21-residue-long thanatin displays broad-spectrum activity against both Gram-negative and Gram-positive bacteria as well as against various species of fungi. Remarkably, thanatin was found to be highly potent in inhibiting the growth of bacteria and fungi at considerably low concentrations. Although thanatin was isolated around 25 years ago, only recently has there been a pronounced interest in understanding its mode of action and activity against drug-resistant bacteria. In this review, multiple modes of action of thanatin in killing bacteria and in vivo activity, therapeutic potential are discussed. This promising AMP requires further research for the development of novel molecules for the treatment of infections caused by drug resistant pathogens.
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Affiliation(s)
- Rachita Dash
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore;
- Department of Systems and Computational Biology, School of Life Sciences, University of Hyderabad, Hyderabad, Telangana 500046, India
| | - Surajit Bhattacharjya
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore;
- Correspondence:
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5
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Soni P, Gangurde SS, Ortega-Beltran A, Kumar R, Parmar S, Sudini HK, Lei Y, Ni X, Huai D, Fountain JC, Njoroge S, Mahuku G, Radhakrishnan T, Zhuang W, Guo B, Liao B, Singam P, Pandey MK, Bandyopadhyay R, Varshney RK. Functional Biology and Molecular Mechanisms of Host-Pathogen Interactions for Aflatoxin Contamination in Groundnut ( Arachis hypogaea L.) and Maize ( Zea mays L.). Front Microbiol 2020; 11:227. [PMID: 32194520 PMCID: PMC7063101 DOI: 10.3389/fmicb.2020.00227] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 01/30/2020] [Indexed: 12/26/2022] Open
Abstract
Aflatoxins are secondary metabolites produced by soilborne saprophytic fungus Aspergillus flavus and closely related species that infect several agricultural commodities including groundnut and maize. The consumption of contaminated commodities adversely affects the health of humans and livestock. Aflatoxin contamination also causes significant economic and financial losses to producers. Research efforts and significant progress have been made in the past three decades to understand the genetic behavior, molecular mechanisms, as well as the detailed biology of host-pathogen interactions. A range of omics approaches have facilitated better understanding of the resistance mechanisms and identified pathways involved during host-pathogen interactions. Most of such studies were however undertaken in groundnut and maize. Current efforts are geared toward harnessing knowledge on host-pathogen interactions and crop resistant factors that control aflatoxin contamination. This study provides a summary of the recent progress made in enhancing the understanding of the functional biology and molecular mechanisms associated with host-pathogen interactions during aflatoxin contamination in groundnut and maize.
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Affiliation(s)
- Pooja Soni
- International Crops Research Institute for the Semi-Arid Tropics, Hyderabad, India
| | - Sunil S. Gangurde
- International Crops Research Institute for the Semi-Arid Tropics, Hyderabad, India
| | | | - Rakesh Kumar
- International Crops Research Institute for the Semi-Arid Tropics, Hyderabad, India
| | - Sejal Parmar
- International Crops Research Institute for the Semi-Arid Tropics, Hyderabad, India
| | - Hari K. Sudini
- International Crops Research Institute for the Semi-Arid Tropics, Hyderabad, India
| | - Yong Lei
- Oil Crops Research Institute, Chinese Academy of Agricultural Sciences, Wuhan, China
| | - Xinzhi Ni
- Crop Genetics and Breeding Research Unit, United States Department of Agriculture – Agriculture Research Service, Tifton, GA, United States
| | - Dongxin Huai
- Oil Crops Research Institute, Chinese Academy of Agricultural Sciences, Wuhan, China
| | - Jake C. Fountain
- Department of Plant Pathology, University of Georgia, Tifton, GA, United States
| | - Samuel Njoroge
- International Crops Research Institute for the Semi-Arid Tropics, Lilongwe, Malawi
| | - George Mahuku
- International Institute of Tropical Agriculture, Dar es Salaam, Tanzania
| | | | - Weijian Zhuang
- Oil Crops Research Institute, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Baozhu Guo
- Crop Protection and Management Research Unit, United States Department of Agriculture – Agricultural Research Service, Tifton, GA, United States
| | - Boshou Liao
- Oil Crops Research Institute, Chinese Academy of Agricultural Sciences, Wuhan, China
| | - Prashant Singam
- Department of Genetics, Osmania University, Hyderabad, India
| | - Manish K. Pandey
- International Crops Research Institute for the Semi-Arid Tropics, Hyderabad, India
| | | | - Rajeev K. Varshney
- International Crops Research Institute for the Semi-Arid Tropics, Hyderabad, India
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Study on Antiviral Activity of Two Recombinant Antimicrobial Peptides Against Tobacco Mosaic Virus. Probiotics Antimicrob Proteins 2019; 11:1370-1378. [PMID: 30887308 DOI: 10.1007/s12602-019-09539-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Antimicrobial peptides (AMPs) are generally small peptides with less than 50 amino acid residues, which have been considered as the first line of defense system in plants and animals. These small cationic peptides belong to a family of antimicrobials that are multifunctional effectors of innate immunity. The direct antimicrobial activity of AMPs against different bacteria, viruses, fungi, and parasites has been confirmed in different studies. In this study, the antiviral activity of two recombinant AMPs named thanatin and lactoferricin+lactoferrampin was evaluated against Tobacco mosaic virus (TMV) using half-leaf and leaf disk methods under in vivo and in vitro condition, respectively. The obtained result indicated that both recombinant AMPs have shown an antiviral activity against TMV. Compared to the chimeric lactoferricin+lactoferrampin, recombinant thanatin showed a higher rate of antiviral activity against TMV. Three types of effects, including protective, curative, and inactivation, were evaluated during an antiviral activity test. In the present study, the antiviral activity of two recombinant AMPs is represented for the first time: thanatin and chimeric lactoferricin+lactoferrampin against TMV as a viral plant pathogen.
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Morais TP, Zaini PA, Chakraborty S, Gouran H, Carvalho CP, Almeida-Souza HO, Souza JB, Santos PS, Goulart LR, Luz JMQ, Nascimento R, Dandekar AM. The plant-based chimeric antimicrobial protein SlP14a-PPC20 protects tomato against bacterial wilt disease caused by Ralstonia solanacearum. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2019; 280:197-205. [PMID: 30823998 DOI: 10.1016/j.plantsci.2018.11.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 11/01/2018] [Accepted: 11/26/2018] [Indexed: 06/09/2023]
Abstract
Cecropin-B (CecB) is a peptide with well-established antimicrobial properties against different phytopathogenic bacteria. Despite modest action against Ralstonia solanacearum, its animal source limits the acceptance in transgenic applications. To overcome this, we selected eight alpha-helical (AH) cationic peptides derived from plant protein sequences and investigated their antimicrobial properties against R. solanacearum. Remarkably, PPC20 (a linear AH-peptide present in phosphoenolpyruvate carboxylase) has a three-fold lower lethal dose on R. solanacearum than CecB and lower toxicity to human intestinal epithelial cells. Linking PPC20 to SlP14a (part of a pathogenesis-related protein) established an apoplast-targeted protein providing a means of secreting and stabilizing the antimicrobial peptide in the plant compartment colonized by the pathogen. SlP14a is also a potential antimicrobial, homologous to a human elastase which likely targets outer membrane proteins in Gram-negative bacteria. Recombinant SlP14a-PPC20 showed antibacterial activity against R. solanacearum in vitro, making it a promising candidate for plant protection. This was confirmed with genetically-modified tomato plants engineered to express SlP14a-PPC20, in which bacterial populations in stems were reduced compared to inoculated wild-type control plants. Disease symptoms were also markedly less severe in SlP14a-PPC20-expressing plants, demonstrating a viable strategy to improve resistance against bacterial wilt in tomato.
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Affiliation(s)
- Tâmara P Morais
- Institute of Agricultural Sciences, University of Uberlândia, Uberlândia, 38410-337, MG, Brazil; Institute of Genetics and Biochemistry, University of Uberlândia, Uberlândia, 38400-902, MG, Brazil
| | - Paulo A Zaini
- Department of Plant Sciences, University of California, Davis, 95616, CA, USA
| | - Sandeep Chakraborty
- Department of Plant Sciences, University of California, Davis, 95616, CA, USA
| | - Hossein Gouran
- Department of Plant Sciences, University of California, Davis, 95616, CA, USA
| | - Camila P Carvalho
- Department of Plant Pathology, University of São Paulo, Piracicaba, SP, 13418-900 Brazil
| | - Hebréia O Almeida-Souza
- Institute of Genetics and Biochemistry, University of Uberlândia, Uberlândia, 38400-902, MG, Brazil
| | - Jessica B Souza
- Institute of Genetics and Biochemistry, University of Uberlândia, Uberlândia, 38400-902, MG, Brazil
| | - Paula S Santos
- Institute of Genetics and Biochemistry, University of Uberlândia, Uberlândia, 38400-902, MG, Brazil
| | - Luiz R Goulart
- Institute of Genetics and Biochemistry, University of Uberlândia, Uberlândia, 38400-902, MG, Brazil; Department of Plant Sciences, University of California, Davis, 95616, CA, USA
| | - José M Q Luz
- Institute of Agricultural Sciences, University of Uberlândia, Uberlândia, 38410-337, MG, Brazil
| | - Rafael Nascimento
- Institute of Genetics and Biochemistry, University of Uberlândia, Uberlândia, 38400-902, MG, Brazil; Department of Plant Sciences, University of California, Davis, 95616, CA, USA
| | - Abhaya M Dandekar
- Department of Plant Sciences, University of California, Davis, 95616, CA, USA.
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8
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Ojiambo PS, Battilani P, Cary JW, Blum BH, Carbone I. Cultural and Genetic Approaches to Manage Aflatoxin Contamination: Recent Insights Provide Opportunities for Improved Control. PHYTOPATHOLOGY 2018; 108:1024-1037. [PMID: 29869954 DOI: 10.1094/phyto-04-18-0134-rvw] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Aspergillus flavus is a morphologically complex species that can produce the group of polyketide derived carcinogenic and mutagenic secondary metabolites, aflatoxins, as well as other secondary metabolites such as cyclopiazonic acid and aflatrem. Aflatoxin causes aflatoxicosis when aflatoxins are ingested through contaminated food and feed. In addition, aflatoxin contamination is a major problem, from both an economic and health aspect, in developing countries, especially Asia and Africa, where cereals and peanuts are important food crops. Earlier measures for control of A. flavus infection and consequent aflatoxin contamination centered on creating unfavorable environments for the pathogen and destroying contaminated products. While development of atoxigenic (nonaflatoxin producing) strains of A. flavus as viable commercial biocontrol agents has marked a unique advance for control of aflatoxin contamination, particularly in Africa, new insights into the biology and sexuality of A. flavus are now providing opportunities to design improved atoxigenic strains for sustainable biological control of aflatoxin. Further, progress in the use of molecular technologies such as incorporation of antifungal genes in the host and host-induced gene silencing, is providing knowledge that could be harnessed to develop germplasm that is resistant to infection by A. flavus and aflatoxin contamination. This review summarizes the substantial progress that has been made to understand the biology of A. flavus and mitigate aflatoxin contamination with emphasis on maize. Concepts developed to date can provide a basis for future research efforts on the sustainable management of aflatoxin contamination.
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Affiliation(s)
- Peter S Ojiambo
- First and fifth authors: Center for Integrated Fungal Research, Department of Entomology and Plant Pathology, North Carolina State University, Raleigh 27695; second author: Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy; third author: U.S. Department of Agriculture-Agriculture Research Service, SRRC, New Orleans, LA 70124; and fourth author: Department of Plant Pathology, University of Arkansas, Fayetteville 72701
| | - Paola Battilani
- First and fifth authors: Center for Integrated Fungal Research, Department of Entomology and Plant Pathology, North Carolina State University, Raleigh 27695; second author: Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy; third author: U.S. Department of Agriculture-Agriculture Research Service, SRRC, New Orleans, LA 70124; and fourth author: Department of Plant Pathology, University of Arkansas, Fayetteville 72701
| | - Jeffrey W Cary
- First and fifth authors: Center for Integrated Fungal Research, Department of Entomology and Plant Pathology, North Carolina State University, Raleigh 27695; second author: Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy; third author: U.S. Department of Agriculture-Agriculture Research Service, SRRC, New Orleans, LA 70124; and fourth author: Department of Plant Pathology, University of Arkansas, Fayetteville 72701
| | - Burt H Blum
- First and fifth authors: Center for Integrated Fungal Research, Department of Entomology and Plant Pathology, North Carolina State University, Raleigh 27695; second author: Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy; third author: U.S. Department of Agriculture-Agriculture Research Service, SRRC, New Orleans, LA 70124; and fourth author: Department of Plant Pathology, University of Arkansas, Fayetteville 72701
| | - Ignazio Carbone
- First and fifth authors: Center for Integrated Fungal Research, Department of Entomology and Plant Pathology, North Carolina State University, Raleigh 27695; second author: Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy; third author: U.S. Department of Agriculture-Agriculture Research Service, SRRC, New Orleans, LA 70124; and fourth author: Department of Plant Pathology, University of Arkansas, Fayetteville 72701
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Rajasekaran K, Sayler RJ, Sickler CM, Majumdar R, Jaynes JM, Cary JW. Control of Aspergillus flavus growth and aflatoxin production in transgenic maize kernels expressing a tachyplesin-derived synthetic peptide, AGM182. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2018; 270:150-156. [PMID: 29576068 DOI: 10.1016/j.plantsci.2018.02.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 01/28/2018] [Accepted: 02/07/2018] [Indexed: 06/08/2023]
Abstract
Aspergillus flavus is an opportunistic, saprophytic fungus that infects maize and other fatty acid-rich food and feed crops and produces toxic and carcinogenic secondary metabolites known as aflatoxins. Contamination of maize with aflatoxin poses a serious threat to human health in addition to reducing the crop value leading to a substantial economic loss. Here we report designing a tachyplesin1-derived synthetic peptide AGM182 and testing its antifungal activity both in vitro and in planta. In vitro studies showed a five-fold increase in antifungal activity of AGM182 (vs. tachyplesin1) against A. flavus. Transgenic maize plants expressing AGM182 under maize Ubiquitin-1 promoter were produced through Agrobacterium-mediated transformation. PCR products confirmed integration of the AGM182 gene, while RT-PCR of maize RNA confirmed the presence of AGM182 transcripts. Maize kernel screening assay using a highly aflatoxigenic A. flavus strain (AF70) showed up to 72% reduction in fungal growth in the transgenic AGM182 seeds compared to isogenic negative control seeds. Reduced fungal growth in the AGM182 transgenic seeds resulted in a significant reduction in aflatoxin levels (76-98%). The results presented here show the power of computational and synthetic biology to rationally design and synthesize an antimicrobial peptide against A. flavus that is effective in reducing fungal growth and aflatoxin contamination in an economically important food and feed crop such as maize.
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Affiliation(s)
- Kanniah Rajasekaran
- Food and Feed Safety Research Unit, USDA-ARS, Southern Regional Research Center, New Orleans, LA 70124, United States.
| | - Ronald J Sayler
- Department of Plant Pathology, University of Arkansas, Fayetteville, AR 72701, United States
| | - Christine M Sickler
- Food and Feed Safety Research Unit, USDA-ARS, Southern Regional Research Center, New Orleans, LA 70124, United States
| | - Rajtilak Majumdar
- Food and Feed Safety Research Unit, USDA-ARS, Southern Regional Research Center, New Orleans, LA 70124, United States
| | - Jesse M Jaynes
- College of Agriculture, Environment and Nutrition Sciences, Tuskegee University, Tuskegee, AL 36088, United States
| | - Jeffrey W Cary
- Food and Feed Safety Research Unit, USDA-ARS, Southern Regional Research Center, New Orleans, LA 70124, United States
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Bhatnagar D, Rajasekaran K, Gilbert M, Cary J, Magan N. Advances in molecular and genomic research to safeguard food and feed supply from aflatoxin contamination. WORLD MYCOTOXIN J 2018. [DOI: 10.3920/wmj2017.2283] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Worldwide recognition that aflatoxin contamination of agricultural commodities by the fungus Aspergillus flavus is a global problem has significantly benefitted from global collaboration for understanding the contaminating fungus, as well as for developing and implementing solutions against the contamination. The effort to address this serious food and feed safety issue has led to a detailed understanding of the taxonomy, ecology, physiology, genomics and evolution of A. flavus, as well as strategies to reduce or control pre-harvest aflatoxin contamination, including (1) biological control, using atoxigenic aspergilli, (2) proteomic and genomic analyses for identifying resistance factors in maize as potential breeding markers to enable development of resistant maize lines, and (3) enhancing host-resistance by bioengineering of susceptible crops, such as cotton, maize, peanut and tree nuts. A post-harvest measure to prevent the occurrence of aflatoxin contamination in storage is also an important component for reducing exposure of populations worldwide to aflatoxins in food and feed supplies. The effect of environmental changes on aflatoxin contamination levels has recently become an important aspect for study to anticipate future contamination levels. The ability of A. flavus to produce dozens of secondary metabolites, in addition to aflatoxins, has created a new avenue of research for understanding the role these metabolites play in the survival and biodiversity of this fungus. The understanding of A. flavus, the aflatoxin contamination problem, and control measures to prevent the contamination has become a unique example for an integrated approach to safeguard global food and feed safety.
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Affiliation(s)
- D. Bhatnagar
- US Department of Agriculture, Agricultural Research Service, 1100 Robert E. Lee Boulevard, New Orleans, LA 70124, USA
| | - K. Rajasekaran
- US Department of Agriculture, Agricultural Research Service, 1100 Robert E. Lee Boulevard, New Orleans, LA 70124, USA
| | - M. Gilbert
- US Department of Agriculture, Agricultural Research Service, 1100 Robert E. Lee Boulevard, New Orleans, LA 70124, USA
| | - J.W. Cary
- US Department of Agriculture, Agricultural Research Service, 1100 Robert E. Lee Boulevard, New Orleans, LA 70124, USA
| | - N. Magan
- Applied Mycology Group, Cranfield University, MK45 4DT, Cranfield, United Kingdom
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Majumdar R, Rajasekaran K, Sickler C, Lebar M, Musungu BM, Fakhoury AM, Payne GA, Geisler M, Carter-Wientjes C, Wei Q, Bhatnagar D, Cary JW. The Pathogenesis-Related Maize Seed ( PRms) Gene Plays a Role in Resistance to Aspergillus flavus Infection and Aflatoxin Contamination. FRONTIERS IN PLANT SCIENCE 2017; 8:1758. [PMID: 29089952 PMCID: PMC5651032 DOI: 10.3389/fpls.2017.01758] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 09/25/2017] [Indexed: 05/26/2023]
Abstract
Aspergillus flavus is an opportunistic plant pathogen that colonizes and produces the toxic and carcinogenic secondary metabolites, aflatoxins, in oil-rich crops such as maize (Zea mays ssp. mays L.). Pathogenesis-related (PR) proteins serve as an important defense mechanism against invading pathogens by conferring systemic acquired resistance in plants. Among these, production of the PR maize seed protein, ZmPRms (AC205274.3_FG001), has been speculated to be involved in resistance to infection by A. flavus and other pathogens. To better understand the relative contribution of ZmPRms to A. flavus resistance and aflatoxin production, a seed-specific RNA interference (RNAi)-based gene silencing approach was used to develop transgenic maize lines expressing hairpin RNAs to target ZmPRms. Downregulation of ZmPRms in transgenic kernels resulted in a ∼250-350% increase in A. flavus infection accompanied by a ∼4.5-7.5-fold higher accumulation of aflatoxins than control plants. Gene co-expression network analysis of RNA-seq data during the A. flavus-maize interaction identified ZmPRms as a network hub possibly responsible for regulating several downstream candidate genes associated with disease resistance and other biochemical functions. Expression analysis of these candidate genes in the ZmPRms-RNAi lines demonstrated downregulation (vs. control) of a majority of these ZmPRms-regulated genes during A. flavus infection. These results are consistent with a key role of ZmPRms in resistance to A. flavus infection and aflatoxin accumulation in maize kernels.
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Affiliation(s)
- Rajtilak Majumdar
- Food and Feed Safety Research Unit, United States Department of Agriculture – Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Kanniah Rajasekaran
- Food and Feed Safety Research Unit, United States Department of Agriculture – Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Christine Sickler
- Food and Feed Safety Research Unit, United States Department of Agriculture – Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Matthew Lebar
- Food and Feed Safety Research Unit, United States Department of Agriculture – Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Bryan M. Musungu
- Department of Plant Biology, Southern Illinois University, Carbondale, IL, United States
- Warm Water Aquaculture Unit, United States Department of Agriculture – Agricultural Research Service, Stoneville, MS, United States
| | - Ahmad M. Fakhoury
- Department of Plant, Soil and Agriculture Systems, Southern Illinois University, Carbondale, IL, United States
| | - Gary A. Payne
- Department of Plant Pathology, North Carolina State University, Raleigh, NC, United States
| | - Matt Geisler
- Department of Plant Biology, Southern Illinois University, Carbondale, IL, United States
| | - Carol Carter-Wientjes
- Food and Feed Safety Research Unit, United States Department of Agriculture – Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Qijian Wei
- Food and Feed Safety Research Unit, United States Department of Agriculture – Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Deepak Bhatnagar
- Food and Feed Safety Research Unit, United States Department of Agriculture – Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Jeffrey W. Cary
- Food and Feed Safety Research Unit, United States Department of Agriculture – Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
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Breen S, Solomon PS, Bedon F, Vincent D. Surveying the potential of secreted antimicrobial peptides to enhance plant disease resistance. FRONTIERS IN PLANT SCIENCE 2015; 6:900. [PMID: 26579150 PMCID: PMC4621407 DOI: 10.3389/fpls.2015.00900] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 10/09/2015] [Indexed: 05/20/2023]
Abstract
Antimicrobial peptides (AMPs) are natural products found across diverse taxa as part of the innate immune system against pathogen attacks. Some AMPs are synthesized through the canonical gene expression machinery and are called ribosomal AMPs. Other AMPs are assembled by modular enzymes generating nonribosomal AMPs and harbor unusual structural diversity. Plants synthesize an array of AMPs, yet are still subject to many pathogen invasions. Crop breeding programs struggle to release new cultivars in which complete disease resistance is achieved, and usually such resistance becomes quickly overcome by the targeted pathogens which have a shorter generation time. AMPs could offer a solution by exploring not only plant-derived AMPs, related or unrelated to the crop of interest, but also non-plant AMPs produced by bacteria, fungi, oomycetes or animals. This review highlights some promising candidates within the plant kingdom and elsewhere, and offers some perspectives on how to identify and validate their bioactivities. Technological advances, particularly in mass spectrometry (MS) and nuclear magnetic resonance (NMR), have been instrumental in identifying and elucidating the structure of novel AMPs, especially nonribosomal peptides which cannot be identified through genomics approaches. The majority of non-plant AMPs showing potential for plant disease immunity are often tested using in vitro assays. The greatest challenge remains the functional validation of candidate AMPs in plants through transgenic experiments, particularly introducing nonribosomal AMPs into crops.
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Affiliation(s)
- Susan Breen
- Plant Sciences Division, Research School of Biology, The Australian National UniversityCanberra, ACT, Australia
| | - Peter S. Solomon
- Plant Sciences Division, Research School of Biology, The Australian National UniversityCanberra, ACT, Australia
| | - Frank Bedon
- Department of Economic Development, AgriBioBundoora, VIC, Australia
- AgriBio, La Trobe UniversityBundoora, VIC, Australia
| | - Delphine Vincent
- Department of Economic Development, AgriBioBundoora, VIC, Australia
- *Correspondence: Delphine Vincent
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