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Tominello-Ramirez CS, Muñoz Hoyos L, Oubounyt M, Stam R. Network analyses predict major regulators of resistance to early blight disease complex in tomato. BMC PLANT BIOLOGY 2024; 24:641. [PMID: 38971719 PMCID: PMC11227178 DOI: 10.1186/s12870-024-05366-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2024] [Accepted: 07/01/2024] [Indexed: 07/08/2024]
Abstract
BACKGROUND Early blight and brown leaf spot are often cited as the most problematic pathogens of tomato in many agricultural regions. Their causal agents are Alternaria spp., a genus of Ascomycota containing numerous necrotrophic pathogens. Breeding programs have yielded quantitatively resistant commercial cultivars, but fungicide application remains necessary to mitigate the yield losses. A major hindrance to resistance breeding is the complexity of the genetic determinants of resistance and susceptibility. In the absence of sufficiently resistant germplasm, we sequenced the transcriptomes of Heinz 1706 tomatoes treated with strongly virulent and weakly virulent isolates of Alternaria spp. 3 h post infection. We expanded existing functional gene annotations in tomato and using network statistics, we analyzed the transcriptional modules associated with defense and susceptibility. RESULTS The induced responses are very distinct. The weakly virulent isolate induced a defense response of calcium-signaling, hormone responses, and transcription factors. These defense-associated processes were found in a single transcriptional module alongside secondary metabolite biosynthesis genes, and other defense responses. Co-expression and gene regulatory networks independently predicted several D clade ethylene response factors to be early regulators of the defense transcriptional module, as well as other transcription factors both known and novel in pathogen defense, including several JA-associated genes. In contrast, the strongly virulent isolate elicited a much weaker response, and a separate transcriptional module bereft of hormone signaling. CONCLUSIONS Our findings have predicted major defense regulators and several targets for downstream functional analyses. Combined with our improved gene functional annotation, they suggest that defense is achieved through induction of Alternaria-specific immune pathways, and susceptibility is mediated by modulating hormone responses. The implication of multiple specific clade D ethylene response factors and upregulation of JA-associated genes suggests that host defense in this pathosystem involves ethylene response factors to modulate jasmonic acid signaling.
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Affiliation(s)
- Christopher S Tominello-Ramirez
- Department of Phytopathology and Crop Protection, Institute for Phytopathology, Christian Albrechts University, Kiel, Germany
- Phytopathology, TUM School of Life Sciences Weihenstephan, Technical University of Munich, Freising, Germany
| | - Lina Muñoz Hoyos
- Phytopathology, TUM School of Life Sciences Weihenstephan, Technical University of Munich, Freising, Germany
| | - Mhaned Oubounyt
- Institute for Computational Systems Biology, University of Hamburg, Hamburg, Germany
| | - Remco Stam
- Department of Phytopathology and Crop Protection, Institute for Phytopathology, Christian Albrechts University, Kiel, Germany.
- Phytopathology, TUM School of Life Sciences Weihenstephan, Technical University of Munich, Freising, Germany.
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Xiao S, Wang J, Bai Z, Pan Y, Li Q, Zhao D, Zhang D, Yang Z, Zhu J. Alternaria solani effectors AsCEP19 and AsCEP20 reveal novel functions in pathogenicity and conidiogenesis. Microbiol Spectr 2024:e0421423. [PMID: 38912810 DOI: 10.1128/spectrum.04214-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 04/15/2024] [Indexed: 06/25/2024] Open
Abstract
Previous work identified a pair of specific effectors AsCEP19 and AsCEP20 in Alternaria solani as contributors to the virulence of A. solani. Here, we constructed AsCEP19 and AsCEP20 deletion mutants in A. solani strain HWC168 to further reveal the effects of these genes on the biology and pathogenicity of A. solani. Deletion of AsCEP19 and AsCEP20 did not affect vegetative growth but did affect conidial maturation, with an increase in the percentage of abnormal conidia produced. Furthermore, we determined the expression patterns of genes involved in the conidiogenesis pathway and found that the regulatory gene abaA was significantly upregulated and chsA, a positive regulator for conidiation, was significantly downregulated in the mutant strains compared to the wild-type strain. These results suggest that AsCEP19 and AsCEP20 indirectly affect the conidial development and maturation of A. solani. Pathogenicity assays revealed significantly impaired virulence of ΔAsCEP19, ΔAsCEP20, and ΔAsCEP19 + AsCEP20 mutants on potato and tomato plants. Moreover, we performed localization assays with green fluorescent protein-tagged proteins in chili pepper leaves. We found that AsCEP19 can specifically localize to the chloroplasts of chili pepper epidermal cells, while AsCEP20 can localize to both chloroplasts and the plasma membrane. Weighted gene co-expression network analysis revealed enrichment of genes of this module in the photosynthesis pathway, with many hub genes associated with chloroplast structure and photosynthesis. These results suggest that chloroplasts are the targets for AsCEP19 and AsCEP20. IMPORTANCE Alternaria solani is an important necrotrophic pathogen causing potato early blight. Previous studies have provide preliminary evidence that specific effectors AsCEP19 and AsCEP20 contribute to virulence, but their respective functions, localization, and pathogenic mechanisms during the infection process of A. solani remain unclear. Here, we have systematically studied the specific effectors AsCEP19 and AsCEP20 for the first time, which are essential for conidial maturation. The deletion of AsCEP19 and AsCEP20 can significantly impair fungal pathogenicity. Additionally, we preliminarily revealed that AsCEP19 and AsCEP20 target the chloroplasts of host cells. Our findings further enhance our understanding of the molecular mechanisms underlying the virulence of necrotrophic pathogens.
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Affiliation(s)
- Siyu Xiao
- College of Plant Protection, Hebei Agricultural University, Baoding, Hebei, China
| | - Jinhui Wang
- College of Plant Protection, Hebei Agricultural University, Baoding, Hebei, China
- Technological Innovation Center for Biological Control of Crop Diseases and Insect Pests of Hebei Province, Baoding, Hebei, China
| | - Zihan Bai
- College of Plant Protection, Hebei Agricultural University, Baoding, Hebei, China
| | - Yang Pan
- College of Plant Protection, Hebei Agricultural University, Baoding, Hebei, China
| | - Qian Li
- College of Plant Protection, Hebei Agricultural University, Baoding, Hebei, China
| | - Dongmei Zhao
- College of Plant Protection, Hebei Agricultural University, Baoding, Hebei, China
| | - Dai Zhang
- College of Plant Protection, Hebei Agricultural University, Baoding, Hebei, China
| | - Zhihui Yang
- College of Plant Protection, Hebei Agricultural University, Baoding, Hebei, China
- Technological Innovation Center for Biological Control of Crop Diseases and Insect Pests of Hebei Province, Baoding, Hebei, China
| | - Jiehua Zhu
- College of Plant Protection, Hebei Agricultural University, Baoding, Hebei, China
- Technological Innovation Center for Biological Control of Crop Diseases and Insect Pests of Hebei Province, Baoding, Hebei, China
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Muñoz Hoyos L, Anisha WP, Meng C, Kleigrewe K, Dawid C, Hückelhoven R, Stam R. Untargeted metabolomics reveals PTI-associated metabolites. PLANT, CELL & ENVIRONMENT 2024; 47:1224-1237. [PMID: 38164085 DOI: 10.1111/pce.14794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 12/09/2023] [Accepted: 12/13/2023] [Indexed: 01/03/2024]
Abstract
Plants employ a multilayered immune system to combat pathogens. In one layer, recognition of Pathogen- or Microbe-Associated Molecular Patterns or elicitors, triggers a cascade that leads to defence against the pathogen and Pattern Triggered Immunity. Secondary or specialised metabolites (SMs) are expected to play a role, because they are potentially anti-fungal compounds. Tomato (Solanum lycopersicum) plants inoculated with Alternaria solani s.l. show symptoms of infection after inoculation. Plants inoculated with Alternaria alternata remain symptomless. We hypothesised that pattern-triggered induction of resistance related metabolites in tomato contributes to the resistance against A. alternata. We compared the metabolomic profile (metabolome) of tomato after treatments with A. alternata, A. solani and the fungal elicitor chitin, and identified SMs involved in early defence of tomato plants. We revealed differential metabolome fingerprints. The composition of A. alternata and chitin induced metabolomes show larger overlap with each other than with the A. solani induced metabolome. We identify 65 metabolites possibly associated with PTI in tomato plants, including NAD and trigonelline. We confirm that trigonelline inhibits fungal growth in vitro at physiological concentrations. Thus, a true pattern-triggered, chemical defence is mounted against A. alternata, which contains anti-fungal compounds that could be interesting for crop protection strategies.
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Affiliation(s)
- Lina Muñoz Hoyos
- Chair of Phytopathology, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Wan Petra Anisha
- Chair of Phytopathology, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Chen Meng
- TUM School of Life Sciences, Bavarian Center for Biomolecular Mass Spectrometry, Technical University of Munich, Freising, Germany
| | - Karin Kleigrewe
- TUM School of Life Sciences, Bavarian Center for Biomolecular Mass Spectrometry, Technical University of Munich, Freising, Germany
| | - Corinna Dawid
- TUM School of Life Sciences, Bavarian Center for Biomolecular Mass Spectrometry, Technical University of Munich, Freising, Germany
- Chair of Food Chemistry and Molecular Sensory Science, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
- Functional Phytometabolomics, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Ralph Hückelhoven
- Chair of Phytopathology, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Remco Stam
- Chair of Phytopathology, TUM School of Life Sciences, Technical University of Munich, Freising, Germany
- Department of Phytopathology and Crop protection, Institute of Phytopathology, Kiel University, Kiel, Germany
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Schmey T, Tominello-Ramirez CS, Brune C, Stam R. Alternaria diseases on potato and tomato. MOLECULAR PLANT PATHOLOGY 2024; 25:e13435. [PMID: 38476108 DOI: 10.1111/mpp.13435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 01/27/2024] [Accepted: 01/29/2024] [Indexed: 03/14/2024]
Abstract
Alternaria spp. cause different diseases in potato and tomato crops. Early blight caused by Alternaria solani and brown spot caused by Alternaria alternata are most common, but the disease complex is far more diverse. We first provide an overview of the Alternaria species infecting the two host plants to alleviate some of the confusion that arises from the taxonomic rearrangements in this fungal genus. Highlighting the diversity of Alternaria fungi on both solanaceous hosts, we review studies investigating the genetic diversity and genomes, before we present recent advances from studies elucidating host-pathogen interactions and fungicide resistances. TAXONOMY Kingdom Fungi, Phylum Ascomycota, Class Dothideomycetes, Order Pleosporales, Family Pleosporaceae, Genus Alternaria. BIOLOGY AND HOST RANGE Alternaria spp. adopt diverse lifestyles. We specifically review Alternaria spp. that cause disease in the two solanaceous crops potato (Solanum tuberosum) and tomato (Solanum lycopersicum). They are necrotrophic pathogens with no known sexual stage, despite some signatures of recombination. DISEASE SYMPTOMS Symptoms of the early blight/brown spot disease complex include foliar lesions that first present as brown spots, depending on the species with characteristic concentric rings, which eventually lead to severe defoliation and considerable yield loss. CONTROL Good field hygiene can keep the disease pressure low. Some potato and tomato cultivars show differences in susceptibility, but there are no fully resistant varieties known. Therefore, the main control mechanism is treatment with fungicides.
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Affiliation(s)
- Tamara Schmey
- TUM School of Life Science Weihenstephan, Technical University of Munich, Freising, Germany
| | - Christopher S Tominello-Ramirez
- Department of Phytopathology and Crop Protection, Institute of Phytopathology, Christian Albrechts University, Kiel, Germany
| | - Carolin Brune
- TUM School of Life Science Weihenstephan, Technical University of Munich, Freising, Germany
| | - Remco Stam
- Department of Phytopathology and Crop Protection, Institute of Phytopathology, Christian Albrechts University, Kiel, Germany
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