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Nan Y, Zhang M, Li Y, Bi Y. The G-protein alpha subunit AaGA1 positively regulates vegetative growth, appressorium-like formation, and pathogenicity in Alternaria alternata. J Appl Microbiol 2024; 135:lxae198. [PMID: 39104199 DOI: 10.1093/jambio/lxae198] [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] [Received: 05/16/2024] [Revised: 07/09/2024] [Accepted: 08/02/2024] [Indexed: 08/07/2024]
Abstract
AIMS The Gα subunit is a major component of heterotrimeric G proteins, which play a crucial role in the development and pathogenicity of several model fungi. However, its detailed function in the causal agent of pear black spot (Alternaria alternata) is unclear. Our aim was to understand the characteristics and functions of AaGA1 in A. alternata. METHODS AND RESULTS AaGA1 was cloned from A. alternata in this study, which encodes 353 amino acids and has a "G-alpha" domain. Mutant ΔAaGA1 resulted in reduced vegetative growth, conidiation, and spore germination. Especially, mutant ΔAaGA1 produced only fewer conidia on the V8A medium, and spore formation-related genes AbaA, BrlA, and WetA were significantly downregulated. More tolerance against cell wall-inhibiting agents was observed after the deletion of AaGA1. Moreover, AaGA1 deletion led to a significant reduction in melanin and toxin production. Interestingly, deletion of AaGA1 resulted in defective appressorium-like formations, complete loss of the ability to penetrate cellophane, and decreased infection on non-wound inoculated tobacco leaves. Cell wall-degrading enzyme-related genes PME, CL, Cut2, and LC were significantly downregulated in mutant ΔAaGA1 mutant, significantly reducing virulence on wound-inoculated pear fruits. CONCLUSIONS The G protein alpha subunit AaGA1 is indispensable for fungal development, appressorium-like formations, and pathogenicity in A. alternata.
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Affiliation(s)
- Yuanping Nan
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Miao Zhang
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Yongcai Li
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Yang Bi
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
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2
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Li R, Su Z, Sun C, Wu S. Antibacterial insights into alternariol and its derivative alternariol monomethyl ether produced by a marine fungus. Appl Environ Microbiol 2024; 90:e0005824. [PMID: 38470179 PMCID: PMC11022538 DOI: 10.1128/aem.00058-24] [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] [Received: 01/11/2024] [Accepted: 02/14/2024] [Indexed: 03/13/2024] Open
Abstract
Alternaria alternata FB1 is a marine fungus identified as a candidate for plastic degradation in our previous study. This fungus has been recently shown to produce secondary metabolites with significant antimicrobial activity against various pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) and the notorious aquaculture pathogen Vibrio anguillarum. The antibacterial compounds were purified and identified as alternariol (AOH) and its derivative, alternariol monomethyl ether (AME). We found that AOH and AME primarily inhibited pathogenic bacteria (MRSA or V. anguillarum) by disordering cell division and some other key physiological and biochemical processes. We further demonstrated that AOH could effectively inhibit the unwinding activity of MRSA topoisomerases, which are closely related to cell division and are the potential action target of AOH. The antibacterial activities of AOH and AME were verified by using zebrafish as the in vivo model. Notably, AOH and AME did not significantly affect the viability of normal human liver cells at concentrations that effectively inhibited MRSA or V. anguillarum. Finally, we developed the genetic operation system of A. alternata FB1 and blocked the biosynthesis of AME by knocking out omtI (encoding an O-methyl transferase), which facilitated A. alternata FB1 to only produce AOH. The development of this system in the marine fungus will accelerate the discovery of novel natural products and further bioactivity study.IMPORTANCEMore and more scientific reports indicate that alternariol (AOH) and its derivative alternariol monomethyl ether (AME) exhibit antibacterial activities. However, limited exploration of their detailed antibacterial mechanisms has been performed. In the present study, the antibacterial mechanisms of AOH and AME produced by the marine fungus Alternaria alternata FB1 were disclosed in vitro and in vivo. Given their low toxicity on the normal human liver cell line under the concentrations exhibiting significant antibacterial activity against different pathogens, AOH and AME are proposed to be good candidates for developing promising antibiotics against methicillin-resistant Staphylococcus aureus and Vibrio anguillarum. We also succeeded in blocking the biosynthesis of AME, which facilitated us to easily obtain pure AOH. Moreover, based on our previous results, A. alternata FB1 was shown to enable polyethylene degradation.
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Affiliation(s)
- Rongmei Li
- College of Life Sciences, Qingdao University, Qingdao, China
- CAS Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Center for Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, China
- Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
| | - Zhenjie Su
- CAS Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Center for Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, China
- Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
- College of Earth Science, University of Chinese Academy of Sciences, Beijing, China
| | - Chaomin Sun
- CAS Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Center for Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, China
- Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
- College of Earth Science, University of Chinese Academy of Sciences, Beijing, China
| | - Shimei Wu
- College of Life Sciences, Qingdao University, Qingdao, China
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3
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Li R, Li Y, Xu W, Liu W, Xu X, Bi Y, Prusky D. Aabrm1-mediated melanin synthesis is essential to growth and development, stress adaption, and pathogenicity in Alternaria alternata. Front Microbiol 2024; 14:1327765. [PMID: 38274752 PMCID: PMC10808324 DOI: 10.3389/fmicb.2023.1327765] [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: 10/25/2023] [Accepted: 12/22/2023] [Indexed: 01/27/2024] Open
Abstract
Scytalone dehydratase (brm1) is one of the key enzymes in 1, 8-dihydroxynaphthalene (DHN) melanin synthesis, which mediates melanin biosythesis and regulates cell biological process of plant fungi, but its function in Alternaria alternata, the causal agent of pear black spot, is unclear. Brm1 in A. alternata was cloned, identified, and named as Aabrm1. An Aabrm1-deletion mutant was generated and revealed that the deletion of Aabrm1 leads to a significant decrease in melanin production and forms orange colony smooth spores. In addition, the deletion of Aabrm1 gene impaired infection structure information and penetration. The external stress resistance of ΔAabrm1 was significantly weakened, and, in particular, it is very sensitive to oxidative stress, and the contents of H2O2 and O2.- in ΔAabrm1 were significantly increased. Virulence of ΔAabrm1 was reduced in non-wound-inoculated pear leaves but not changed in wound-inoculated pear fruit. These results indicated that Aabrm1-mediated melanin synthesis plays an important role in the pathogenicity of A. alternata.
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Affiliation(s)
- Rong Li
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou, China
| | - Yongcai Li
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou, China
| | - Wenyi Xu
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou, China
| | - Wenjuan Liu
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou, China
| | - Xiaobin Xu
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou, China
| | - Yang Bi
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou, China
| | - Dov Prusky
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou, China
- Department of Postharvest Science of Fresh Produce, Agricultural Research Organization, Bet Dagan, Israel
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4
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Jiang Q, Li Y, Mao R, Bi Y, Liu Y, Zhang M, Li R, Yang Y, Prusky DB. AaCaMKs Positively Regulate Development, Infection Structure Differentiation and Pathogenicity in Alternaria alternata, Causal Agent of Pear Black Spot. Int J Mol Sci 2023; 24:ijms24021381. [PMID: 36674895 PMCID: PMC9865007 DOI: 10.3390/ijms24021381] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 12/29/2022] [Accepted: 01/09/2023] [Indexed: 01/13/2023] Open
Abstract
Calcium/calmodulin-dependent protein kinase (CaMK), a key downstream target protein in the Ca2+ signaling pathway of eukaryotes, plays an important regulatory role in the growth, development and pathogenicity of plant fungi. Three AaCaMKs (AaCaMK1, AaCaMK2 and AaCaMK3) with conserved PKC_like superfamily domains, ATP binding sites and ACT sites have been cloned from Alternaria alternata, However, their regulatory mechanism in A. alternata remains unclear. In this study, the function of the AaCaMKs in the development, infection structure differentiation and pathogenicity of A. alternata was elucidated through targeted gene disruption. The single disruption of AaCaMKs had no impact on the vegetative growth and spore morphology but significantly influenced hyphae growth, sporulation, biomass accumulation and melanin biosynthesis. Further expression analysis revealed that the AaCaMKs were up-regulated during the infection structure differentiation of A. alternata on hydrophobic and pear wax substrates. In vitro and in vivo analysis further revealed that the deletion of a single AaCaMKs gene significantly reduced the A. alternata conidial germination, appressorium formation and infection hyphae formation. In addition, pharmacological analysis confirmed that the CaMK specific inhibitor, KN93, inhibited conidial germination and appressorium formation in A. alternata. Meanwhile, the AaCaMKs genes deficiency significantly reduced the A. alternata pathogenicity. These results demonstrate that AaCaMKs regulate the development, infection structure differentiation and pathogenicity of A. alternata and provide potential targets for new effective fungicides.
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Affiliation(s)
- Qianqian Jiang
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Yongcai Li
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
- Correspondence: ; Tel.: +86-931-763-1694
| | - Renyan Mao
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Yang Bi
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Yongxiang Liu
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Miao Zhang
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Rong Li
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Yangyang Yang
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Dov B. Prusky
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
- Institute of Postharvest and Food Sciences, The Volcani Center, Agricultural Research Organization, Rishon LeZion 7505101, Israel
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5
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Huang Y, Li YC, Li DM, Bi Y, Liu YX, Mao RY, Zhang M, Jiang QQ, Wang XJ, Prusky D. Molecular Characterization of Phospholipase C in Infection Structure Differentiation Induced by Pear Fruit Surface Signals, Stress Responses, Secondary Metabolism, and Virulence of Alternaria alternata. PHYTOPATHOLOGY 2022; 112:2207-2217. [PMID: 35612304 DOI: 10.1094/phyto-11-21-0475-r] [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: 06/15/2023]
Abstract
Fungal pathogens use plant surface physiochemical signals to trigger specific developmental processes. To assess the role of phospholipase C (PLC) in mediating plant stimuli sensing of Alternaria alternata, the function of three PLC genes was characterized by constructing ΔAaPLC mutants. Here we showed that fruit wax-coated surfaces significantly induced appressorium formation in A. alternata and mutants. Germination of ΔAaPLC mutants did not differ from the wild type. Deletion of AaPLC1 led to the decrease of appressorium formation and infected hyphae, but the degree of reduction varies between the different types of waxes, with the strongest response to pear wax. Appressorium formation and infected hyphae of the ΔAaPLC1 mutant on dewaxed onion epidermis mounted with pear wax (θ4) were reduced by 14.5 and 65.7% after 8 h incubation, while ΔAaPLC2 and ΔAaPLC3 formed the same infection hyphae as wild type. In addition, AaPLC1 mutation caused pleiotropic effects on fungal biological function, including growth deficiency, changes in stress tolerance, weakening of pathogenicity to the host, as well as destruction of mycotoxin synthesis. Both AaPLC2 and AaPLC3 genes were found to have some effects on stress response and mycotoxin production. Taken together, AaPLC genes differentially regulate the growth, stress response, pathogenicity, and secondary metabolism of A. alternata.
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Affiliation(s)
- Yi Huang
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Yong-Cai Li
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Dong-Mei Li
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Yang Bi
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Yong-Xiang Liu
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Ren-Yan Mao
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Miao Zhang
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Qian-Qian Jiang
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Xiao-Jing Wang
- College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China
| | - Dov Prusky
- Department of Postharvest Science of Fresh Produce, Agricultural Research Organization, The 12 Volcani Center, Beit Dagan 50200, Israel
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6
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Jiang Q, Mao R, Li Y, Bi Y, Liu Y, Zhang M, Li R, Yang Y, Dov B P.
AaCaM
is required for infection structure differentiation and secondary metabolites in pear fungal pathogen
Alternaria alternata. J Appl Microbiol 2022; 133:2631-2641. [DOI: 10.1111/jam.15732] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 06/12/2022] [Accepted: 07/20/2022] [Indexed: 11/29/2022]
Affiliation(s)
- Qianqian Jiang
- College of Food Science and Engineering Gansu Agricultural University Lanzhou China
| | - Renyan Mao
- College of Food Science and Engineering Gansu Agricultural University Lanzhou China
| | - Yongcai Li
- College of Food Science and Engineering Gansu Agricultural University Lanzhou China
| | - Yang Bi
- College of Food Science and Engineering Gansu Agricultural University Lanzhou China
| | - Yongxiang Liu
- College of Food Science and Engineering Gansu Agricultural University Lanzhou China
| | - Miao Zhang
- College of Food Science and Engineering Gansu Agricultural University Lanzhou China
| | - Rong Li
- College of Food Science and Engineering Gansu Agricultural University Lanzhou China
| | - Yangyang Yang
- College of Food Science and Engineering Gansu Agricultural University Lanzhou China
| | - Prusky Dov B
- College of Food Science and Engineering Gansu Agricultural University Lanzhou China
- Institute of Postharvest and Food Sciences The Volcani Center, Agricultural Research Organization Rishon LeZion Israel
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7
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Peel Diffusion and Antifungal Efficacy of Different Fungicides in Pear Fruit: Structure-Diffusion-Activity Relationships. J Fungi (Basel) 2022; 8:jof8050547. [PMID: 35628802 PMCID: PMC9144380 DOI: 10.3390/jof8050547] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Revised: 05/18/2022] [Accepted: 05/20/2022] [Indexed: 01/12/2023] Open
Abstract
Fungal pathogens can invade not only the fruit peel but also the outer part of the fruit mesocarp, limiting the efficacy of fungicides. In this study, the relationships between fungicide structure, diffusion capacity and in vivo efficacy were evaluated for the first time. The diffusion capacity from pear peel to mesocarp of 11 antifungal compounds, including p-aminobenzoic acid, carbendazim, difenoconazole, dipicolinic acid, flusilazole, gentamicin, kojic acid, prochloraz, quinolinic acid, thiophanate methyl and thiram was screened. The obtained results indicated that size and especially polarity were negatively correlated with the diffusion capacity. Although some antifungal compounds, such as prochloraz and carbendazim, were completely degraded after a few days in peel and mesocarp, other compounds, such as p-aminobenzoic acid and kojic acid, showed high stability. When applying the antifungal compounds at the EC50 concentrations, it was observed that the compounds with high diffusion capacity showed higher in vivo antifungal activity against Alternaria alternata than compounds with low diffusion capacity. In contrast, there was no relationship between stability and in vivo efficacy. Collectively, the obtained results indicated that the diffusion capacity plays an important role in the efficacy of fungicides for the control of pear fruit diseases.
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The transmembrane protein AaSho1 is essential for appressorium formation and secondary metabolism but dispensable for vegetative growth in pear fungal Alternaria alternata. Fungal Biol 2021; 126:139-148. [DOI: 10.1016/j.funbio.2021.11.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Revised: 10/16/2021] [Accepted: 11/16/2021] [Indexed: 01/03/2023]
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