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Sweany RR, Mack BM, Gebru ST, Mammel MK, Cary JW, Moore GG, Lebar MD, Carter-Wientjes CH, Gilbert MK. Divergent Aspergillus flavus corn population is composed of prolific conidium producers: Implications for saprophytic disease cycle. Mycologia 2024; 116:536-557. [PMID: 38727560 DOI: 10.1080/00275514.2024.2343645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 04/12/2024] [Indexed: 06/29/2024]
Abstract
The ascomycete fungus Aspergillus flavus infects and contaminates corn, peanuts, cottonseed, and tree nuts with toxic and carcinogenic aflatoxins. Subdivision between soil and host plant populations suggests that certain A. flavus strains are specialized to infect peanut, cotton, and corn despite having a broad host range. In this study, the ability of strains isolated from corn and/or soil in 11 Louisiana fields to produce conidia (field inoculum and male gamete) and sclerotia (resting bodies and female gamete) was assessed and compared with genotypic single-nucleotide polymorphism (SNP) differences between whole genomes. Corn strains produced upward of 47× more conidia than strains restricted to soil. Conversely, corn strains produced as much as 3000× fewer sclerotia than soil strains. Aspergillus flavus strains, typified by sclerotium diameter (small S-strains, <400 μm; large L-strains, >400 μm), belonged to separate clades. Several strains produced a mixture (M) of S and L sclerotia, and an intermediate number of conidia and sclerotia, compared with typical S-strains (minimal conidia, copious sclerotia) and L-strains (copious conidia, minimal sclerotia). They also belonged to a unique phylogenetic mixed (M) clade. Migration from soil to corn positively correlated with conidium production and negatively correlated with sclerotium production. Genetic differences correlated with differences in conidium and sclerotium production. Opposite skews in female (sclerotia) or male (conidia) gametic production by soil or corn strains, respectively, resulted in reduced effective breeding population sizes when comparing male:female gamete ratio with mating type distribution. Combining both soil and corn populations increased the effective breeding population, presumably due to contribution of male gametes from corn, which fertilize sclerotia on the soil surface. Incongruencies between aflatoxin clusters, strain morphotype designation, and whole genome phylogenies suggest a history of sexual reproduction within this Louisiana population, demonstrating the importance of conidium production, as infectious propagules and as fertilizers of the A. flavus soil population.
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Affiliation(s)
- Rebecca R Sweany
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Brian M Mack
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Solomon T Gebru
- Division of Virulence Assessment, Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, Maryland, 20708
| | - Mark K Mammel
- Division of Molecular Biology, Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, Maryland, 20708
| | - Jeffrey W Cary
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Geromy G Moore
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Matthew D Lebar
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Carol H Carter-Wientjes
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
| | - Matthew K Gilbert
- Food and Feed Safety Research Unit, Southern Regional Research Center, U.S. Department of Agriculture, New Orleans, Louisiana, 70124
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Geng Q, Hu J, Xu P, Sun T, Qiu H, Wang S, Song F, Shen L, Li Y, Liu M, Peng X, Tian J, Yang K. The Autophagy-Related Protein ATG8 Orchestrates Asexual Development and AFB1 Biosynthesis in Aspergillus flavus. J Fungi (Basel) 2024; 10:349. [PMID: 38786704 PMCID: PMC11122632 DOI: 10.3390/jof10050349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2024] [Revised: 05/08/2024] [Accepted: 05/11/2024] [Indexed: 05/25/2024] Open
Abstract
Autophagy, a conserved cellular recycling process, plays a crucial role in maintaining homeostasis under stress conditions. It also regulates the development and virulence of numerous filamentous fungi. In this study, we investigated the specific function of ATG8, a reliable autophagic marker, in the opportunistic pathogen Aspergillus flavus. To investigate the role of atg8 in A. flavus, the deletion and complemented mutants of atg8 were generated according to the homologous recombination principle. Deletion of atg8 showed a significant decrease in conidiation, spore germination, and sclerotia formation compared to the WT and atg8C strains. Additionally, aflatoxin production was found severely impaired in the ∆atg8 mutant. The stress assays demonstrated that ATG8 was important for A. flavus response to oxidative stress. The fluorescence microscopy showed increased levels of reactive oxygen species in the ∆atg8 mutant cells, and the transcriptional result also indicated that genes related to the antioxidant system were significantly reduced in the ∆atg8 mutant. We further found that ATG8 participated in regulating the pathogenicity of A. flavus on crop seeds. These results revealed the biological role of ATG8 in A. flavus, which might provide a potential target for the control of A. flavus and AFB1 biosynthesis.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - Xue Peng
- JSNU-UWEC Joint Laboratory of Jiangsu Province Colleges and Universities, School of Life Science, Jiangsu Normal University, Xuzhou 221116, China; (Q.G.); (J.H.); (P.X.); (T.S.); (H.Q.); (S.W.); (F.S.); (L.S.); (Y.L.); (M.L.)
| | - Jun Tian
- JSNU-UWEC Joint Laboratory of Jiangsu Province Colleges and Universities, School of Life Science, Jiangsu Normal University, Xuzhou 221116, China; (Q.G.); (J.H.); (P.X.); (T.S.); (H.Q.); (S.W.); (F.S.); (L.S.); (Y.L.); (M.L.)
| | - Kunlong Yang
- JSNU-UWEC Joint Laboratory of Jiangsu Province Colleges and Universities, School of Life Science, Jiangsu Normal University, Xuzhou 221116, China; (Q.G.); (J.H.); (P.X.); (T.S.); (H.Q.); (S.W.); (F.S.); (L.S.); (Y.L.); (M.L.)
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Moore GG, Mack BM, Wendt KL, Castano-Duque L, Anderson VM, Cichewicz RH. Genomic and metabolomic diversity within a familial population of Aspergillus flavus. Mol Microbiol 2024; 121:927-939. [PMID: 38396382 DOI: 10.1111/mmi.15244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 01/12/2024] [Accepted: 02/11/2024] [Indexed: 02/25/2024]
Abstract
Aspergillus flavus is an agriculturally significant micro-fungus having potential to contaminate food and feed crops with toxic secondary metabolites such as aflatoxin (AF) and cyclopiazonic acid (CPA). Research has shown A. flavus strains can overcome heterokaryon incompatibility and undergo meiotic recombination as teleomorphs. Although evidence of recombination in the AF gene cluster has been reported, the impacts of recombination on genotype and metabolomic phenotype in a single generation are lacking. In previous studies, we paired an aflatoxigenic MAT1-1 A. flavus strain with a non-aflatoxigenic MAT1-2 A. flavus strain that had been tagged with green fluorescent protein and then 10 F1 progenies (a mix of fluorescent and non-fluorescent) were randomly selected from single-ascospore colonies and broadly examined for evidence of recombination. In this study, we determined four of those 10 F1 progenies were recombinants because they were not vegetatively compatible with either parent or their siblings, and they exhibited other distinctive traits that could only result from meiotic recombination. The other six progenies examined shared genomic identity with the non-aflatoxigenic, fluorescent, and MAT1-2 parent, but were metabolically distinct. This study highlights phenotypic and genomic changes that may occur in a single generation from the outcrossing of sexually compatible strains of A. flavus.
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Affiliation(s)
- Geromy G Moore
- Southern Regional Research Center, USDA-ARS, New Orleans, Louisiana, USA
| | - Brian M Mack
- Southern Regional Research Center, USDA-ARS, New Orleans, Louisiana, USA
| | - Karen L Wendt
- Department of Chemistry and Biochemistry, Natural Products Discovery Group, Stephenson Life Sciences Research Center, University of Oklahoma, Norman, Oklahoma, USA
| | - Lina Castano-Duque
- Southern Regional Research Center, USDA-ARS, New Orleans, Louisiana, USA
| | - Victoria M Anderson
- Department of Chemistry and Biochemistry, Natural Products Discovery Group, Stephenson Life Sciences Research Center, University of Oklahoma, Norman, Oklahoma, USA
| | - Robert H Cichewicz
- Department of Chemistry and Biochemistry, Natural Products Discovery Group, Stephenson Life Sciences Research Center, University of Oklahoma, Norman, Oklahoma, USA
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Calvo AM, Dabholkar A, Wyman EM, Lohmar JM, Cary JW. Regulatory functions of homeobox domain transcription factors in fungi. Appl Environ Microbiol 2024; 90:e0220823. [PMID: 38421174 PMCID: PMC10952592 DOI: 10.1128/aem.02208-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2024] Open
Abstract
Homeobox domain (HD) proteins present a crucial involvement in morphological differentiation and other functions in eukaryotes. Most HD genes encode transcription factors (TFs) that orchestrate a regulatory role in cellular and developmental decisions. In fungi, multiple studies have increased our understanding of these important HD regulators in recent years. These reports have revealed their role in fungal development, both sexual and asexual, as well as their importance in governing other biological processes in these organisms, including secondary metabolism, pathogenicity, and sensitivity to environmental stresses. Here, we provide a comprehensive review of the current knowledge on the regulatory roles of HD-TFs in fungi, with a special focus on Aspergillus species.
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Affiliation(s)
- A. M. Calvo
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
| | - A. Dabholkar
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
| | - E. M. Wyman
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
| | - J. M. Lohmar
- Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, Louisiana, USA
| | - J. W. Cary
- Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, Louisiana, USA
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Atehnkeng J, Ojiambo PS, Ortega-Beltran A, Augusto J, Cotty PJ, Bandyopadhyay R. Impact of frequency of application on the long-term efficacy of the biocontrol product Aflasafe in reducing aflatoxin contamination in maize. Front Microbiol 2022; 13:1049013. [PMID: 36504767 PMCID: PMC9732863 DOI: 10.3389/fmicb.2022.1049013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 10/31/2022] [Indexed: 11/25/2022] Open
Abstract
Aflatoxins, produced by several Aspergillus section Flavi species in various crops, are a significant public health risk and a barrier to trade and development. In sub-Saharan Africa, maize and groundnut are particularly vulnerable to aflatoxin contamination. Aflasafe, a registered aflatoxin biocontrol product, utilizes atoxigenic A. flavus genotypes native to Nigeria to displace aflatoxin producers and mitigate aflatoxin contamination. Aflasafe was evaluated in farmers' fields for 3 years, under various regimens, to quantify carry-over of the biocontrol active ingredient genotypes. Nine maize fields were each treated either continuously for 3 years, the first two successive years, in year 1 and year 3, or once during the first year. For each treated field, a nearby untreated field was monitored. Aflatoxins were quantified in grain at harvest and after simulated poor storage. Biocontrol efficacy and frequencies of the active ingredient genotypes decreased in the absence of annual treatment. Maize treated consecutively for 2 or 3 years had significantly (p < 0.05) less aflatoxin (92% less) in grain at harvest than untreated maize. Maize grain from treated fields subjected to simulated poor storage had significantly less (p < 0.05) aflatoxin than grain from untreated fields, regardless of application regimen. Active ingredients occurred at higher frequencies in soil and grain from treated fields than from untreated fields. The incidence of active ingredients recovered in soil was significantly correlated (r = 0.898; p < 0.001) with the incidence of active ingredients in grain, which in turn was also significantly correlated (r = -0.621, p = 0.02) with aflatoxin concentration. Although there were carry-over effects, caution should be taken when drawing recommendations about discontinuing biocontrol use. Cost-benefit analyses of single season and carry-over influences are needed to optimize use by communities of smallholder farmers in sub-Saharan Africa.
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Affiliation(s)
- Joseph Atehnkeng
- Pathology and Mycotoxin, International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria
| | - Peter S. Ojiambo
- Pathology and Mycotoxin, International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria,Center for Integrated Fungal Research, Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC, United States
| | - Alejandro Ortega-Beltran
- Pathology and Mycotoxin, International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria
| | - Joao Augusto
- Pathology and Mycotoxin, International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria
| | - Peter J. Cotty
- College of Food Science and Engineering, Ocean University of China, Qingdao, China,Agricultural Research Service, United States Department of Agriculture, Tucson, AZ, United States
| | - Ranajit Bandyopadhyay
- Pathology and Mycotoxin, International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria,*Correspondence: Ranajit Bandyopadhyay,
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Luis JM, Carbone I, Mack BM, Lebar MD, Cary JW, Gilbert MK, Bhatnagar D, Wientjes CC, Payne GA, Moore GG, Ameen YO, Ojiambo PS. Dataset for transcriptomic profiles associated with development of sexual structures in Aspergillus flavus. Data Brief 2022; 42:108033. [PMID: 35330736 PMCID: PMC8938862 DOI: 10.1016/j.dib.2022.108033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 03/04/2022] [Indexed: 11/17/2022] Open
Abstract
Information on the transcriptomic changes that occur within sclerotia of Aspergillus flavus during its sexual cycle is very limited and warrants further research. The findings will broaden our knowledge of the biology of A. flavus and can provide valuable insights in the development or deployment of non-toxigenic strains as biocontrol agents against aflatoxigenic strains. This article presents transcriptomic datasets included in our research article entitled, “Development of sexual structures influences metabolomic and transcriptomic profiles in Aspergillus flavus” [1], which utilized transcriptomics to identify possible genes and gene clusters associated with sexual reproduction and fertilization in A. flavus. RNA was extracted from sclerotia of a high fertility cross (Hi-Fert-Mated), a low fertility cross (Lo-Fert-Mated), and unmated strains (Hi-Fert-Unmated and Lo-Fert-Unmated) of A. flavus collected immediately after crossing and at every two weeks until eight weeks of incubation on mixed cereal agar at 30 °C in continuous darkness (n = 4 replicates from each treatment for each time point; 80 total). Raw sequencing reads obtained on an Illumina NovaSeq 6000 were deposited in NCBI's Sequence Read Archive (SRA) repository under BioProject accession number PRJNA789260. Reads were mapped to the A. flavus NRRL 3357 genome (assembly JCVI-afl1-v2.0; GCA_000006275.2) using STAR software. Differential gene expression analyses, functional analyses, and weighted gene co-expression network analysis were performed using DESeq2 R packages. The raw and analyzed data presented in this article could be reused for comparisons with other datasets to obtain transcriptional differences among strains of A. flavus or closely related species. The data can also be used for further investigation of the molecular basis of different processes involved in sexual reproduction and sclerotia fertility in A. flavus.
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Development of sexual structures influences metabolomic and transcriptomic profiles in Aspergillus flavus. Fungal Biol 2022; 126:187-200. [DOI: 10.1016/j.funbio.2022.01.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 01/19/2022] [Accepted: 01/20/2022] [Indexed: 01/02/2023]
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Sarkar S, Ramsey AF, Cazenave AB, Balota M. Peanut Leaf Wilting Estimation From RGB Color Indices and Logistic Models. FRONTIERS IN PLANT SCIENCE 2021; 12:658621. [PMID: 34220885 PMCID: PMC8253229 DOI: 10.3389/fpls.2021.658621] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 03/30/2021] [Indexed: 06/13/2023]
Abstract
Peanut (Arachis hypogaea L.) is an important crop for United States agriculture and worldwide. Low soil moisture is a major constraint for production in all peanut growing regions with negative effects on yield quantity and quality. Leaf wilting is a visual symptom of low moisture stress used in breeding to improve stress tolerance, but visual rating is slow when thousands of breeding lines are evaluated and can be subject to personnel scoring bias. Photogrammetry might be used instead. The objective of this article is to determine if color space indices derived from red-green-blue (RGB) images can accurately estimate leaf wilting for breeding selection and irrigation triggering in peanut production. RGB images were collected with a digital camera proximally and aerially by a unmanned aerial vehicle during 2018 and 2019. Visual rating was performed on the same days as image collection. Vegetation indices were intensity, hue, saturation, lightness, a∗, b∗, u∗, v∗, green area (GA), greener area (GGA), and crop senescence index (CSI). In particular, hue, a∗, u∗, GA, GGA, and CSI were significantly (p ≤ 0.0001) associated with leaf wilting. These indices were further used to train an ordinal logistic regression model for wilting estimation. This model had 90% accuracy when images were taken aerially and 99% when images were taken proximally. This article reports on a simple yet key aspect of peanut screening for tolerance to low soil moisture stress and uses novel, fast, cost-effective, and accurate RGB-derived models to estimate leaf wilting.
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Affiliation(s)
- Sayantan Sarkar
- School of Plant and Environmental Sciences, Virginia Tech, Tidewater AREC, Suffolk, VA, United States
| | - A. Ford Ramsey
- Department of Agricultural and Applied Economics, Virginia Tech, Blacksburg, VA, United States
| | - Alexandre-Brice Cazenave
- School of Plant and Environmental Sciences, Virginia Tech, Tidewater AREC, Suffolk, VA, United States
| | - Maria Balota
- School of Plant and Environmental Sciences, Virginia Tech, Tidewater AREC, Suffolk, VA, United States
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Moore GG. Practical considerations will ensure the continued success of pre-harvest biocontrol using non-aflatoxigenic Aspergillus flavus strains. Crit Rev Food Sci Nutr 2021; 62:4208-4225. [PMID: 33506687 DOI: 10.1080/10408398.2021.1873731] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
There is an important reason for the accelerated use of non-aflatoxigenic Aspergillus flavus to mitigate pre-harvest aflatoxin contamination… it effectively addresses the imperative need for safer food and feed. Now that we have decades of proof of the effectiveness of A. flavus as biocontrol, it is time to improve several aspects of this strategy. If we are to continue relying heavily on this form of aflatoxin mitigation, there are considerations we must acknowledge, and actions we must take, to ensure that we are best wielding this strategy to our advantage. These include its: (1) potential to produce other mycotoxins, (2) persistence in the field in light of several ecological factors, (3) its reproductive and genetic stability, (4) the mechanism(s) employed that allow it to elicit control over aflatoxigenic strains and species of agricultural importance and (5) supplemental alternatives that increase its effectiveness. There is a need to be consistent, practical and thoughtful when it comes to implementing this method of mycotoxin mitigation since these fungi are living organisms that have been adapting, evolving and surviving on this planet for tens-of-millions of years. This document will serve as a critical review of the literature regarding pre-harvest A. flavus biocontrol and will discuss opportunities for improvements.
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Affiliation(s)
- Geromy G Moore
- United States Department of Agriculture, Agricultural Research Service, New Orleans, USA
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