Cleavage of the Babuvirus Movement Protein B4 into Functional Peptides Capable of Host Factor Conjugation is Required for Virulence
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Banana bunchy top virus (BBTV) poses a serious danger to banana crops worldwide. BBTV-encoded protein B4 is a determinant of pathogenicity. However, the relevant molecular mechanisms underlying its effects remain unknown. In this study, we found that a functional peptide could be liberated from protein B4, likely via proteolytic processing. Site-directed mutagenesis indicated that the functional processing of protein B4 is required for its pathogenic effects, including dwarfism and sterility, in plants. The released protein fragment targets host proteins, such as the large subunit of RuBisCO (RbcL) and elongation factor 2 (EF2), involved in protein synthesis. Therefore, the peptide released from B4 (also a precursor) may act as a non-canonical modifier to influence host–pathogen interactions involving BBTV and plants.
KeywordsBanana bunchy top virus (BBTV) Movement protein B4 Functional peptide Pathogenicity
This work was supported by grants from the Natural Science Foundation of China (No. 31301641 to J.Z.) and the Program for Qualified Personnel of Taiwan Strait West Coast (No. K8812007 to L.H.X.). We are grateful to Haitao Wang for assistance with TEM, Dr. Zhixin Liu for providing the anti-B3 (coat protein) antibody, and Dr. Zhenguo Du for valuable discussions.
JZ conceived of the entire project. JZ and WL performed the vast majority of experiments. PS generated some plasmid constructs and performed Western blotting. TW was involved in TEM analyses. ZW provided materials, including banana samples. LX provided constructive suggestions and co-supervised the project. JZ generated or guided all figures. JZ and CJC interpreted the data and wrote the manuscript.
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Conflict of interest
The authors declare that they have no conflict of interest.
Animal and Human Rights Statement
The authors declare that they have no conflict of interest. This article does not contain any studies with human or animal subjects performed by any of the authors.
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