1
|
Zhang Z, Guo W, Lu Y, Kang Q, Sui L, Liu H, Zhao Y, Zou X, Li Q. Hypovirulence-associated mycovirus epidemics cause pathogenicity degeneration of Beauveria bassiana in the field. Virol J 2023; 20:255. [PMID: 37924080 PMCID: PMC10623766 DOI: 10.1186/s12985-023-02217-6] [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: 08/17/2023] [Accepted: 10/26/2023] [Indexed: 11/06/2023] Open
Abstract
BACKGROUND The entomogenous fungus Beauveria bassiana is used as a biological insecticide worldwide, wild B. bassiana strains with high pathogenicity in the field play an important role in controlling insect pests via not only screening of highly virulent strains but also natural infection, but the pathogenicity degeneration of wild strains severely affected aforementioned effects. Previous studies have showed that multiple factors contributed to this phenomenon. It has been extensively proved that the mycovirus infection caused hypovirulence of phytopathogenic fungi, which has been used for plant disease biocontrol. However, it remains unknown whether the mycovirus epidemics is a key factor causing hypovirulence of B. bassiana naturally in the field. METHODS Wild strains of B. bassiana were collected from different geographic locations in Jilin Province, China, to clarify the epidemic and diversity of the mycoviruses. A mycovirus Beauveria bassiana chrysovirus 2 (BbCV2) we have previously identified was employed to clarify its impact on the pathogenicity of host fungi B. bassiana against the larvae of insect pest Ostrinia furnacalis. The serological analysis was conducted by preparing polyclonal antibody against a BbCV2 coat protein, to determine whether it can dissociate outside the host fungal cells and subsequently infect new hosts. Transcriptome analysis was used to reveal the interactions between viruses and hosts. RESULTS We surprisingly found that the mycovirus BbCV2 was prevalent in the field as a core virus in wild B. bassiana strains, without obvious genetic differentiation, this virus possessed efficient and stable horizontal and vertical transmission capabilities. The serological results showed that the virus could not only replicate within but also dissociate outside the host cells, and the purified virions could infect B. bassiana by co-incubation. The virus infection causes B. bassiana hypovirulence. Transcriptome analysis revealed decreased expression of genes related to insect epidermis penetration, hypha growth and toxin metabolism in B. bassiana caused by mycovirus infection. CONCLUSION Beauveria bassiana infected by hypovirulence-associated mycovirus can spread the virus to new host strains after infecting insects, and cause the virus epidemics in the field. The findings confirmed that mycovirus infection may be an important factor affecting the pathogenicity degradation of B. bassiana in the field.
Collapse
Affiliation(s)
- Zhengkun Zhang
- Institute of Plant Protection, Jilin Academy of Agricultural Sciences, Jilin Key Laboratory of Agricultural Microbiology, Key Laboratory of Integrated Pest Management on Crops in Northeast China, Ministry of Agriculture and Rural Areas, Changchun, 130033, People's Republic of China
| | - Wenbo Guo
- Institute of Plant Protection, Jilin Academy of Agricultural Sciences, Jilin Key Laboratory of Agricultural Microbiology, Key Laboratory of Integrated Pest Management on Crops in Northeast China, Ministry of Agriculture and Rural Areas, Changchun, 130033, People's Republic of China
- College of Plant Protection, Jilin Agricultural University, Changchun, 130118, People's Republic of China
| | - Yang Lu
- Institute of Plant Protection, Jilin Academy of Agricultural Sciences, Jilin Key Laboratory of Agricultural Microbiology, Key Laboratory of Integrated Pest Management on Crops in Northeast China, Ministry of Agriculture and Rural Areas, Changchun, 130033, People's Republic of China
- College of Plant Protection, Jilin Agricultural University, Changchun, 130118, People's Republic of China
| | - Qin Kang
- Institute of Zoology, Chinese Academy of Sciences, Beijing, 101408, People's Republic of China
| | - Li Sui
- Institute of Plant Protection, Jilin Academy of Agricultural Sciences, Jilin Key Laboratory of Agricultural Microbiology, Key Laboratory of Integrated Pest Management on Crops in Northeast China, Ministry of Agriculture and Rural Areas, Changchun, 130033, People's Republic of China
| | - Hongyu Liu
- Institute of Plant Protection, Jilin Academy of Agricultural Sciences, Jilin Key Laboratory of Agricultural Microbiology, Key Laboratory of Integrated Pest Management on Crops in Northeast China, Ministry of Agriculture and Rural Areas, Changchun, 130033, People's Republic of China
| | - Yu Zhao
- Institute of Plant Protection, Jilin Academy of Agricultural Sciences, Jilin Key Laboratory of Agricultural Microbiology, Key Laboratory of Integrated Pest Management on Crops in Northeast China, Ministry of Agriculture and Rural Areas, Changchun, 130033, People's Republic of China
| | - Xiaowei Zou
- Institute of Plant Protection, Jilin Academy of Agricultural Sciences, Jilin Key Laboratory of Agricultural Microbiology, Key Laboratory of Integrated Pest Management on Crops in Northeast China, Ministry of Agriculture and Rural Areas, Changchun, 130033, People's Republic of China
| | - Qiyun Li
- Institute of Plant Protection, Jilin Academy of Agricultural Sciences, Jilin Key Laboratory of Agricultural Microbiology, Key Laboratory of Integrated Pest Management on Crops in Northeast China, Ministry of Agriculture and Rural Areas, Changchun, 130033, People's Republic of China.
- College of Plant Protection, Jilin Agricultural University, Changchun, 130118, People's Republic of China.
- Jilin Agricultural Science and Technology University, Jilin, 132109, People's Republic of China.
| |
Collapse
|
2
|
Functional Analysis of Keto-Acid Reductoisomerase ILVC in the Entomopathogenic Fungus Metarhizium robertsii. J Fungi (Basel) 2021; 7:jof7090737. [PMID: 34575775 PMCID: PMC8471054 DOI: 10.3390/jof7090737] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Revised: 08/31/2021] [Accepted: 09/06/2021] [Indexed: 11/28/2022] Open
Abstract
Ketol-acid reductoisomerase (ILVC) is the second enzyme in the branched-chain amino acid (BCAA) biosynthesis, which regulates many physiological activities in a variety of organisms from bacteria to fungi and plants. In this work, function mechanisms of ILVC in Metarhizium robertsii Metchnikoff (Hypocreales: Clavicipitaceae) were explored with site-directed mutagenesis, reductase activity assays and transcriptomics analysis. The reductase activity assays showed that ILVC from phytopathogenic fungi exhibited significantly higher activities than those from entomopathogenic fungi but lower than those from yeast. Site-directed mutagenesis and enzymatic activities of MrILVC with different active-site mutants (Arg-113, Ser-118, Asp-152, Asp-260, and Glu-264) confirmed that active sites of MrILVC are conserved with plant and bacterial ILVCs. Deleting MrilvC causes the complete failures of vegetative growth and conidial germination, feeding with branched-chain amino acids (BCAAs) recovers the fungal growth but not conidial germination, while both characteristics are restored when supplemented with yeast extract. Compared to ΔMrilvC cultured in czapek agar (CZA), plenty of genes involved in the biosynthesis of antibiotics and amino acids were up- or down-regulated in the wild type or ΔMrilvC feeding with either BCAAs or yeast extract. Further analysis showed some genes, such as catalase A, participate in mycelial growth and conidial germination was down-regulated in ΔMrilvC from CZA, revealing that MrILVC might control the fungal development by gene regulation and BCAAs or yeast extract could play partial roles of MrILVC. This study will advance our understanding of ILVC function mechanisms in fungi.
Collapse
|