Publications by authors named "Huahui Lan"

10 Publications

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The Fungi-specific histone Acetyltransferase Rtt109 mediates morphogenesis, Aflatoxin synthesis and pathogenicity in Aspergillus flavus by acetylating H3K9.

IMA Fungus 2021 Apr 7;12(1). Epub 2021 Apr 7.

Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.

Aspergillus flavus is a common saprophytic filamentous fungus that produces the highly toxic natural compound aflatoxin during its growth process. Synthesis of the aflatoxins, which can contaminate food crops causing huge losses to the agricultural economy, is often regulated by epigenetic modification, such as the histone acetyltransferase. In this study, we used Aspergillus flavus as an experimental model to construct the acetyltransferase gene rtt109 knockout strain (△rtt109) and its complementary strain (△rtt109·com) by homologous recombination. The growth of △rtt109 was significantly suppressed compared to the wild type (WT) strain and the △rtt109·com strain. The sclerotium of △rtt109 grew smaller, and the amount of sclerotia generated by △rtt109 was significantly reduced. The number of conidiums of △rtt109 was significantly reduced, especially on the yeast extract sucrose (YES) solid medium. The amount of aflatoxins synthesized by △rtt109 in the PDB liquid medium was significantly decreased We also found that the △rtt109 strain was extremely sensitive to DNA damage stress. Through the maize seed infection experiment, we found that the growth of △rtt109 on the surface of affected corn was largely reduced, and the amount of aerial mycelium decreased significantly, which was consistent with the results on the artificial medium. We further found that H3K9 was the acetylated target of Rtt109 in A. flavus. In conclusion, Rtt109 participated in the growth, conidium formation, sclerotia generation, aflatoxin synthesis, environmental stress response, regulation of infection of A. flavus. The results from this study of rtt109 showed data for acetylation in the regulation of life processes and provided a new thought regarding the prevention and control of A. flavus hazards.
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http://dx.doi.org/10.1186/s43008-021-00060-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8025522PMC
April 2021

Gas Chromatography-Mass Spectrometry Profiling of Volatile Compounds Reveals Metabolic Changes in a Non-Aflatoxigenic Induced by 5-Azacytidine.

Toxins (Basel) 2020 01 19;12(1). Epub 2020 Jan 19.

Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, 350002 Fuzhou, China.

is one of the most opportunistic pathogens invading many important oilseed crops and foodstuffs with such toxic secondary metabolites as aflatoxin (AF) and Cyclopiazonic acid. We previously used the DNA methylation inhibitor 5-azacytidine to treat with an AF-producing A133 strain, and isolated a mutant (NT) of , which displayed impaired abilities of AF biosynthesis and fungal development. In this study, gas chromatography-mass spectrometry (GC-MS) analysis was used to reveal the metabolic changes between these two strains. A total of 1181 volatiles were identified in these two strains, among which 490 volatiles were found in these two strains in vitro and 332 volatiles were found in vivo. The NT mutant was found to produce decreasing volatile compounds, among which most of the fatty acid-derived volatiles were significantly downregulated in the NT mutant compared to the A133 strain, which are important precursors for AF biosynthesis. Two antioxidants and most of the amino acids derived volatiles were found significantly upregulated in the NT mutant. Overall, our results reveal the difference of metabolic profiles in two different isolates, which may provide valuable information for controlling infections of this fungal pathogen.
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http://dx.doi.org/10.3390/toxins12010057DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7020457PMC
January 2020

Set3 Is Required for Asexual Development, Aflatoxin Biosynthesis, and Fungal Virulence in .

Front Microbiol 2019 29;10:530. Epub 2019 Mar 29.

Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China.

is an opportunistic pathogenic fungus for both plant and animal that produces carcinogenic toxins termed aflatoxins (AFs). To identify possible genetic targets to reduce AF contamination, in this study, we have characterized a novel Set3, and it shares sequence homology with the yeast protein Set3. The deletion mutants present no difference in growth rate but alterations in asexual development and secondary metabolite production when compared to the wild type. Specifically, deletion of gene decreases conidiophore formation and conidial production through downregulating expression of and genes. In addition, normal levels of are required for sclerotial development and expression of sclerotia-related genes and . Further analyses demonstrated that Set3 negatively regulates AF production as well as the concomitant expression of genes in the AF gene cluster. Importantly, our results also display that Set3 is involved in crop kernel colonization. Taking together, these results reveal that a novel Set3 plays crucial roles in morphological development, secondary metabolism, and fungal virulence in .
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http://dx.doi.org/10.3389/fmicb.2019.00530DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6455067PMC
March 2019

The HosA Histone Deacetylase Regulates Aflatoxin Biosynthesis Through Direct Regulation of Aflatoxin Cluster Genes.

Mol Plant Microbe Interact 2019 Sep 31;32(9):1210-1228. Epub 2019 Jul 31.

Fujian Key Laboratory of Pathogenic Fungi Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.

Histone deacetylases (HDACs) always function as corepressors and sometimes as coactivators in the regulation of fungal development and secondary metabolite production. However, the mechanism through which HDACs play positive roles in secondary metabolite production is still unknown. Here, classical HDAC enzymes were identified and analyzed in , a fungus that produces one of the most carcinogenic secondary metabolites, aflatoxin B (AFB1). Characterization of the HDACs revealed that a class I family HDAC, HosA, played crucial roles in growth, reproduction, the oxidative stress response, AFB1 biosynthesis, and pathogenicity. To a lesser extent, a class II family HDAC, HdaA, was also involved in sclerotia formation and AFB1 biosynthesis. An in vitro analysis of HosA revealed that its HDAC activity was considerably diminished at nanomolar concentrations of trichostatin A. Notably, chromatin immunoprecipitation experiments indicated that HosA bound directly to AFB1 biosynthesis cluster genes to regulate their expression. Finally, we found that a transcriptional regulator, SinA, interacts with HosA to regulate fungal development and AFB1 biosynthesis. Overall, our results reveal a novel mechanism by which classical HDACs mediate the induction of secondary metabolite genes in fungi.
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http://dx.doi.org/10.1094/MPMI-01-19-0033-RDOI Listing
September 2019

Cyclase-Associated Protein Cap with Multiple Domains Contributes to Mycotoxin Biosynthesis and Fungal Virulence in Aspergillus flavus.

J Agric Food Chem 2019 Apr 5;67(15):4200-4213. Epub 2019 Apr 5.

Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences , Fujian Agriculture and Forestry University , Fuzhou , Fujian 350002 , People's Republic of China.

In Aspergillus, the cyclic adenosine monophosphate (cAMP) signaling modulates asexual development and mycotoxin biosynthesis. Here, we characterize the cyclase-associated protein Cap in the pathogenic fungus Aspergillus flauvs. The cap disruption mutant exhibited dramatic reduction in hyphal growth, conidiation, and spore germination, while an enhanced production of the sclerotia was observed in this mutant. Importantly, the cap gene was found to be important for mycotoxin biosynthesis and virulence. The domain deletion study demonstrated that each domain played an important role for the Cap protein in regulating cAMP/protein kinase A (PKA) signaling, while only P1 and CARP domains were essential for the full function of Cap. The phosphorylation of Cap at S35 was identified in A. flavus, which was found to play a negligible role for the function of Cap. Overall, our results indicated that Cap with multiple domains engages in mycotoxin production and fungal pathogenicity, which could be designed as potential control targets for preventing this fungal pathogen.
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http://dx.doi.org/10.1021/acs.jafc.8b07115DOI Listing
April 2019

Investigation of Aspergillus flavus in animal virulence.

Toxicon 2018 Apr 2;145:40-47. Epub 2018 Mar 2.

Fujian Key Laboratory of Pathogenic Fungi Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. Electronic address:

Aspergillus flavus is a common fungal pathogen of plants, animals and humans. Recently, many genes of A. flavus have been reported involving in regulation of pathogenesis in crops, but whether these genes are involved in animal virulence is still unknown. Here, we used a previous easy-to-use infection model for A. flavus based on mouse model by intravenous inoculation of A. flavus conidia. The outcome of infections in mice model showed that A. flavus NRRL3357 and laboratory strain CA14 PTS were both in dose dependent manner and highly reproducible. The progress of disease could be monitored by mice survival and histology analysis. Fungal burden analysis indicated it was gradually decreased within 7 days after infection. Moreover, aspergillosis caused by A. flavus significantly up-regulated gene expression levels of immune response mediators, including INF-γ, TNF-α, Dectin-1 and TLR2. Furthermore, the defined deletion A. flavus strains that previously displayed virulence in crop infection were also determined in this mouse model, and the results showed comparable degrees of infection in mice. Our results suggested that intravenous inoculation of conidia could be a suitable model for testing different A. flavus mutants in animal virulence. We hope to use this model to determine distinct A. flavus strains virulence in animals and study novel therapeutic methods to help control fungus diseases in the future.
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http://dx.doi.org/10.1016/j.toxicon.2018.02.043DOI Listing
April 2018

The Putative Histone Methyltransferase DOT1 Regulates Aflatoxin and Pathogenicity Attributes in Aspergillus flavus.

Toxins (Basel) 2017 07 24;9(7). Epub 2017 Jul 24.

Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.

Lysine methyltransferases transfer methyl groups in specific lysine sites, which regulates a variety of important biological processes in eukaryotes. In this study, we characterized a novel homolog of the yeast methyltransferase DOT1 in . , and observed the roles of in . . Deletion of showed a significant decrease in conidiation, but an increase in sclerotia formation. A change in viability to multiple stresses was also found in the Δ mutant. Additionally, aflatoxin (AF) production was found severely impaired in the Δ mutant. Further analysis by qRT-PCR revealed that the transcription of AF structural genes and their regulator gene were prominently suppressed in the Δ mutant. Furthermore, our data revealed that Dot1 is important for colonizing maize seeds in . . Our research indicates that Dot1 is involved in fungal development, aflatoxin biosynthesis and fungal virulence in . , which might provide a potential target for controlling . with new strategies.
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http://dx.doi.org/10.3390/toxins9070232DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5535179PMC
July 2017

Adenylate Cyclase AcyA Regulates Development, Aflatoxin Biosynthesis and Fungal Virulence in .

Front Cell Infect Microbiol 2016 21;6:190. Epub 2016 Dec 21.

Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China.

is one of the most important opportunistic pathogens of crops and animals. The carcinogenic mycotoxin, aflatoxins produced by this pathogen cause a health problem to human and animals. Since cyclic AMP signaling controls a range of physiological processes, like fungal development and infection when responding to extracellular stimuli in fungal pathogens, in this study, we investigated the function of adenylate cyclase, a core component of cAMP signaling, in aflatoxins biosynthesis and virulence on plant seeds in . . A gene replacement strategy was used to generate the deletion mutant of that encodes the adenylate cyclase. Severe defects in fungal growth, sporulation and sclerotia formation were observed in the deletion mutant. The defect in radical growth could be partially rescued by exogenous cAMP analog. The mutant was also significantly reduced in aflatoxins production and virulence. Similar to the former studies in other fungi, The mutant showed enhancing tolerance to oxidative stress, but more sensitive to heat stress. Overall, the pleiotropic defects of the deletion mutant indicates that the cAMP-PKA pathway is involved in fungal development, aflatoxins biosynthesis and plant seed invasion in .
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http://dx.doi.org/10.3389/fcimb.2016.00190DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5175447PMC
August 2017

The Aspergillus flavus Histone Acetyltransferase AflGcnE Regulates Morphogenesis, Aflatoxin Biosynthesis, and Pathogenicity.

Front Microbiol 2016 30;7:1324. Epub 2016 Aug 30.

Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, The Ministry of Education Key Laboratory of Biopesticide and Chemical Biology, and School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China.

Histone acetyltransferases (HATs) help regulate fungal development and the production of secondary metabolites. In this study, we determined that the HAT AflGcnE influenced morphogenesis and aflatoxin biosynthesis in Aspergillus flavus. We observed that AflGcnE localized to the nucleus and cytoplasm during the conidial production and germination stages, while it was located mainly in the nucleus during the hyphal development stage. Deletion of AflgcnE inhibited the growth of A. flavus and decreased the hydrophobicity of the cell surface. The ΔAflgcnE mutant exhibited a lack of asexual sporulation and was unable to generate sclerotia. Additionally, AflgcnE was required to maintain cell wall integrity and genotoxic stress responses. Importantly, the ΔAflgcnE mutant did not produce aflatoxins, which was consistent with a significant down-regulation of aflatoxin gene expression levels. Furthermore, our data revealed that AflgcnE is a pathogenicity factor required for colonizing maize seeds. In summary, we revealed that A. flavus AflGcnE is crucial for morphological development, aflatoxin biosynthesis, stress responses, and pathogenicity. Our findings help clarify the functional divergence of GcnE orthologs, and may provide a possible target for controlling A. flavus infections of agriculturally important crops.
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http://dx.doi.org/10.3389/fmicb.2016.01324DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5003836PMC
September 2016

The DmtA methyltransferase contributes to Aspergillus flavus conidiation, sclerotial production, aflatoxin biosynthesis and virulence.

Sci Rep 2016 Mar 16;6:23259. Epub 2016 Mar 16.

Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.

DNA methylation is essential for epigenetic regulation of gene transcription and development in many animals, plants and fungi. We investigated whether DNA methylation plays a role in the development and secondary metabolism of Aspergillus flavus, identified the DmtA methyltransferase from A. flavus, and produced a dmtA knock-out mutant by replacing the dmtA coding sequence with the pyrG selectable marker. The A. flavus dmtA null mutant lines produced white fluffy mycelium in liquid medium, and displayed a slightly flavescent conidial pigmentation compared with the normal yellow of the wild-type strain when grown on agar. The ΔdmtA lines exhibited decreased conidiation and aflatoxin (AF) biosynthesis, compared with the wild-type line, suggesting that the DmtA knock-out affected the transcriptional level of genes in the AF cluster. In particular, sclerotia development and host colonization were altered in the dmtA null mutants. Green fluorescent protein tagging at the C-terminus of DmtA showed that DmtA localized to the nucleus and cytoplasm. DNA methylation content measurements in the dmtA mutants revealed no widespread DNA methylation in the mutants or wild-type lines. Thus, our findings suggest that DmtA, apart from being a C-5 cytosine methyltransferase in A. flavus, contributes to asexual development, aflatoxin biosynthesis, sclerotial production and virulence.
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http://dx.doi.org/10.1038/srep23259DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4793245PMC
March 2016