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Castano-Duque L, Gilbert MK, Mack BM, Lebar MD, Carter-Wientjes CH, Sickler CM, Cary JW, Rajasekaran K. Flavonoids Modulate the Accumulation of Toxins From Aspergillus flavus in Maize Kernels. FRONTIERS IN PLANT SCIENCE 2021; 12:761446. [PMID: 34899785 PMCID: PMC8662736 DOI: 10.3389/fpls.2021.761446] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 10/15/2021] [Indexed: 06/14/2023]
Abstract
Aspergillus flavus is an opportunistic fungal pathogen capable of producing aflatoxins, potent carcinogenic toxins that accumulate in maize kernels after infection. To better understand the molecular mechanisms of maize resistance to A. flavus growth and aflatoxin accumulation, we performed a high-throughput transcriptomic study in situ using maize kernels infected with A. flavus strain 3357. Three maize lines were evaluated: aflatoxin-contamination resistant line TZAR102, semi-resistant MI82, and susceptible line Va35. A modified genotype-environment association method (GEA) used to detect loci under selection via redundancy analysis (RDA) was used with the transcriptomic data to detect genes significantly influenced by maize line, fungal treatment, and duration of infection. Gene ontology enrichment analysis of genes highly expressed in infected kernels identified molecular pathways associated with defense responses to fungi and other microbes such as production of pathogenesis-related (PR) proteins and lipid bilayer formation. To further identify novel genes of interest, we incorporated genomic and phenotypic field data from a genome wide association analysis with gene expression data, allowing us to detect significantly expressed quantitative trait loci (eQTL). These results identified significant association between flavonoid biosynthetic pathway genes and infection by A. flavus. In planta fungal infections showed that the resistant line, TZAR102, has a higher fold increase of the metabolites naringenin and luteolin than the susceptible line, Va35, when comparing untreated and fungal infected plants. These results suggest flavonoids contribute to plant resistance mechanisms against aflatoxin contamination through modulation of toxin accumulation in maize kernels.
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Hawkins LK, Warburton ML, Tang J, Tomashek J, Alves Oliveira D, Ogunola OF, Smith JS, Williams WP. Survey of Candidate Genes for Maize Resistance to Infection by Aspergillus flavus and/or Aflatoxin Contamination. Toxins (Basel) 2018; 10:E61. [PMID: 29385107 PMCID: PMC5848162 DOI: 10.3390/toxins10020061] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 01/20/2018] [Accepted: 01/24/2018] [Indexed: 12/21/2022] Open
Abstract
Many projects have identified candidate genes for resistance to aflatoxin accumulation or Aspergillus flavus infection and growth in maize using genetic mapping, genomics, transcriptomics and/or proteomics studies. However, only a small percentage of these candidates have been validated in field conditions, and their relative contribution to resistance, if any, is unknown. This study presents a consolidated list of candidate genes identified in past studies or in-house studies, with descriptive data including genetic location, gene annotation, known protein identifiers, and associated pathway information, if known. A candidate gene pipeline to test the phenotypic effect of any maize DNA sequence on aflatoxin accumulation resistance was used in this study to determine any measurable effect on polymorphisms within or linked to the candidate gene sequences, and the results are published here.
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Affiliation(s)
- Leigh K Hawkins
- USDA ARS Corn Host Plant Resistance Research Unit, Mississippi State, MS 39762, USA.
| | - Marilyn L Warburton
- USDA ARS Corn Host Plant Resistance Research Unit, Mississippi State, MS 39762, USA.
| | - Juliet Tang
- USDA FS Durability and Wood Protection Research Unit, Starkville, MS 39759, USA.
| | - John Tomashek
- Integrated Micro-Chromatography Systems LLC, Irmo, SC 29063, USA.
| | - Dafne Alves Oliveira
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Starkville, MS 39762 USA.
| | - Oluwaseun F Ogunola
- Department of Plant and Soil Sciences, Mississippi State University, Starkville, MS 39762, USA.
| | - J Spencer Smith
- USDA ARS Corn Host Plant Resistance Research Unit, Mississippi State, MS 39762, USA.
| | - W Paul Williams
- USDA ARS Corn Host Plant Resistance Research Unit, Mississippi State, MS 39762, USA.
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Chen ZY, Warburton M, Hawkins L, Wei Q, Raruang Y, Brown R, Zhang L, Bhatnagar D. Production of the 14 kDa trypsin inhibitor protein is important for maize resistance against Aspergillus flavus infection/aflatoxin accumulation. WORLD MYCOTOXIN J 2016. [DOI: 10.3920/wmj2015.1890] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Maize (Zea mays L.) is one of the major crops susceptible to Aspergillus flavus Link ex. Fries infection and subsequent aflatoxin contamination. Previous studies found the production of an antifungal 14 kDa trypsin inhibitor (TI) was associated with maize aflatoxin resistance. To further investigate whether the TI plays any direct role in resistance, a TI gene silencing vector was constructed and transformed into maize. Mature kernels were produced from 66 transgenic lines representing 18 independent events. A final total of twelve lines representing four independent events were confirmed positive for transformation, five of which showed significant reduction (63 to 88%) in TI transcript abundance in seedling leaf tissue and seven of which showed significant TI protein reduction (39-85%) in mature kernels. Six of the seven silenced transgenic lines supported higher levels of aflatoxin production compared to negative controls. To further confirm the role of TI in field resistance to aflatoxin accumulation, DNA sequence polymorphisms from within the gene or linked simple sequence repeats were tested in four quantitative trait loci (QTL) mapping populations for QTL effect, and three QTL with log of the odds scores of 11, 4.5, and 3.0 and possibly caused by the TI protein encoding gene were found. Sequence polymorphisms were also tested for association to aflatoxin levels in an association mapping panel, and three single nucleotide polymorphisms were found associated with aflatoxin accumulation (P<0.01). The data from both RNAi and genetic mapping studies demonstrated that production of the TI in maize is important for its resistance to A. flavus infection and/or aflatoxin production.
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Affiliation(s)
- Z.-Y. Chen
- Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA
| | - M.L. Warburton
- Corn Host Plant Resistance Research Unit, U.S. Department of Agriculture-Agricultural Research Service, Mississippi State, MS 39762-9555, USA
| | - L. Hawkins
- Corn Host Plant Resistance Research Unit, U.S. Department of Agriculture-Agricultural Research Service, Mississippi State, MS 39762-9555, USA
| | - Q. Wei
- Southern Regional Research Center, USDA-ARS, New Orleans, LA 70124, USA
| | - Y. Raruang
- Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA
| | - R.L. Brown
- Southern Regional Research Center, USDA-ARS, New Orleans, LA 70124, USA
| | - L. Zhang
- Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA
| | - D. Bhatnagar
- Southern Regional Research Center, USDA-ARS, New Orleans, LA 70124, USA
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Santiago R, Cao A, Butrón A. Genetic Factors Involved in Fumonisin Accumulation in Maize Kernels and Their Implications in Maize Agronomic Management and Breeding. Toxins (Basel) 2015; 7:3267-96. [PMID: 26308050 PMCID: PMC4549750 DOI: 10.3390/toxins7083267] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 08/05/2015] [Accepted: 08/11/2015] [Indexed: 11/23/2022] Open
Abstract
Contamination of maize with fumonisins depends on the environmental conditions; the maize resistance to contamination and the interaction between both factors. Although the effect of environmental factors is a determinant for establishing the risk of kernel contamination in a region, there is sufficient genetic variability among maize to develop resistance to fumonisin contamination and to breed varieties with contamination at safe levels. In addition, ascertaining which environmental factors are the most important in a region will allow the implementation of risk monitoring programs and suitable cultural practices to reduce the impact of such environmental variables. The current paper reviews all works done to address the influence of environmental variables on fumonisin accumulation, the genetics of maize resistance to fumonisin accumulation, and the search for the biochemical and/or structural mechanisms of the maize plant that could be involved in resistance to fumonisin contamination. We also explore the outcomes of breeding programs and risk monitoring of undertaken projects.
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Affiliation(s)
- Rogelio Santiago
- Facultad de Biología, Dpt Biología Vegetal y Ciencias del Suelo, Universidad de Vigo, As Lagoas Marcosende, Vigo 36310, Spain.
- Agrobiología Ambiental, Calidad de Suelos y Plantas (UVIGO), Unidad Asociada a la Misión Biológica de Galicia (CSIC), Pontevedra 36143, Spain.
| | - Ana Cao
- Misión Biológica de Galicia (CSIC), Box 28, Pontevedra 36080, Spain.
| | - Ana Butrón
- Misión Biológica de Galicia (CSIC), Box 28, Pontevedra 36080, Spain.
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Hawkins LK, Mylroie JE, Oliveira DA, Smith JS, Ozkan S, Windham GL, Williams WP, Warburton ML. Characterization of the Maize Chitinase Genes and Their Effect on Aspergillus flavus and Aflatoxin Accumulation Resistance. PLoS One 2015; 10:e0126185. [PMID: 26090679 PMCID: PMC4475072 DOI: 10.1371/journal.pone.0126185] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Accepted: 03/30/2015] [Indexed: 12/31/2022] Open
Abstract
Maize (Zea mays L.) is a crop of global importance, but prone to contamination by aflatoxins produced by fungi in the genus Aspergillus. The development of resistant germplasm and the identification of genes contributing to resistance would aid in the reduction of the problem with a minimal need for intervention by farmers. Chitinolytic enzymes respond to attack by potential pathogens and have been demonstrated to increase insect and fungal resistance in plants. Here, all chitinase genes in the maize genome were characterized via sequence diversity and expression patterns. Recent evolution within this gene family was noted. Markers from within each gene were developed and used to map the phenotypic effect on resistance of each gene in up to four QTL mapping populations and one association panel. Seven chitinase genes were identified that had alleles associated with increased resistance to aflatoxin accumulation and A. flavus infection in field grown maize. The chitinase in bin 1.05 identified a new and highly significant QTL, while chitinase genes in bins 2.04 and 5.03 fell directly beneath the peaks of previously published QTL. The expression patterns of these genes corroborate possible grain resistance mechanisms. Markers from within the gene sequences or very closely linked to them are presented to aid in the use of marker assisted selection to improve this trait.
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Affiliation(s)
- Leigh K. Hawkins
- USDA-ARS Corn Host Plant Resistance Research Unit, Mississippi State, Starkville, MS, United States of America
| | - J. Erik Mylroie
- USDA-ARS Corn Host Plant Resistance Research Unit, Mississippi State, Starkville, MS, United States of America
| | - Dafne A. Oliveira
- Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Mississippi State University, Starkville, MS, 39762, United States of America
| | - J. Spencer Smith
- USDA-ARS Corn Host Plant Resistance Research Unit, Mississippi State, Starkville, MS, United States of America
| | - Seval Ozkan
- Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Mississippi State University, Starkville, MS, 39762, United States of America
| | - Gary L. Windham
- USDA-ARS Corn Host Plant Resistance Research Unit, Mississippi State, Starkville, MS, United States of America
| | - W. Paul Williams
- USDA-ARS Corn Host Plant Resistance Research Unit, Mississippi State, Starkville, MS, United States of America
| | - Marilyn L. Warburton
- USDA-ARS Corn Host Plant Resistance Research Unit, Mississippi State, Starkville, MS, United States of America
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Abstract
Aflatoxin contamination of maize grain is a huge economic and health problem, causing death and increased disease burden in much of the developing world and income loss in the developed world. Despite the gravity of the problem, deployable solutions are still being sought. In the past 15 years, much progress has been made in creating resistant maize inbred lines; mapping of genetic factors associated with resistance; and identifying possible resistance mechanisms. This review highlights this progress, most of which has occurred since the last time a review was published on this topic. Many of the needs highlighted in the last reviews have been addressed, and several solutions, taken together, can now greatly reduce the aflatoxin problem in maize grain. Continued research will soon lead to further solutions, which promise to further reduce and even eliminate the problem completely.
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Henry WB. Maize aflatoxin accumulation segregates with early maturing selections from an S2 breeding cross population. Toxins (Basel) 2013; 5:162-72. [PMID: 23322131 PMCID: PMC3564075 DOI: 10.3390/toxins5010162] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Revised: 01/09/2013] [Accepted: 01/09/2013] [Indexed: 11/22/2022] Open
Abstract
Maize breeders continue to seek new sources of aflatoxin resistance, but most lines identified as resistance sources are late maturing. The vast difference in flowering time makes it hard to cross these lines with proprietary commercial lines that mature much earlier and often subjects the reproductive phase of these resistant lines to the hottest and driest portion of the summer, making silking, pollination and grain fill challenging. Two hundred crosses from the GEM Project were screened for aflatoxin accumulation at Mississippi State in 2008, and a subset of these lines were screened again in 2009. The breeding cross UR13085:S99g99u was identified as a potential source of aflatoxin resistance, and maturity-based selections were made from an S2 breeding population from this same germplasm source: UR13085:S99g99u-B-B. The earliest maturing selections performed poorly for aflatoxin accumulation, but later maturing selections were identified with favorable levels of aflatoxin accumulation. These selections, while designated as "late" within this study, matured earlier than most aflatoxin resistant lines presently available to breeders. Two selections from this study, designated S5_L7 and S5_L8, are potential sources of aflatoxin resistance and will be advanced for line development and additional aflatoxin screening over more site years and environments.
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Affiliation(s)
- W Brien Henry
- Department of Plant and Soil Sciences, Mississippi State University, 117 Dorman Hall, Box 9555, MS 39762, USA.
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Expression analysis of stress-related genes in kernels of different maize (Zea mays L.) inbred lines with different resistance to aflatoxin contamination. Toxins (Basel) 2011; 3:538-50. [PMID: 22069724 PMCID: PMC3202848 DOI: 10.3390/toxins3060538] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Revised: 05/10/2011] [Accepted: 05/14/2011] [Indexed: 11/30/2022] Open
Abstract
This research examined the expression patterns of 94 stress-related genes in seven maize inbred lines with differential expressions of resistance to aflatoxin contamination. The objective was to develop a set of genes/probes associated with resistance to A. flavus and/or aflatoxin contamination. Ninety four genes were selected from previous gene expression studies with abiotic stress to test the differential expression in maize lines, A638, B73, Lo964, Lo1016, Mo17, Mp313E, and Tex6, using real-time RT-PCR. Based on the relative-expression levels, the seven maize inbred lines clustered into two different groups. One group included B73, Lo1016 and Mo17, which had higher levels of aflatoxin contamination and lower levels of overall gene expression. The second group which included Tex6, Mp313E, Lo964 and A638 had lower levels of aflatoxin contamination and higher overall levels of gene expressions. A total of six “cross-talking” genes were identified between the two groups, which are highly expressed in the resistant Group 2 but down-regulated in susceptible Group 1. When further subjected to drought stress, Tex6 expressed more genes up-regulated and B73 has fewer genes up-regulated. The transcript patterns and interactions measured in these experiments indicate that the resistant mechanism is an interconnected process involving many gene products and transcriptional regulators, as well as various host interactions with environmental factors, particularly, drought and high temperature.
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