The invention belongs to the fields of
biotechnology,
protein engineering and
plant protection science, and particularly relates to an antagonistic
protein mutant for cultivating a sweet potato composite
virus disease (SPVD) resistant
plant and application of the antagonistic
protein mutant. The key
pathogenic factor of the SPVD is the RNase3 protein coded by the sweet potato chlorotic stunt
virus (SPCSV), and the RNase3 protein is used as an
RNA silence suppressor (
RSS) to destroy
host immunity. The invention provides an SPCSV-RNase3 antagonistic protein
mutant, which is derived from a natural antagonistic protein, namely a sweet potato
trypsin inhibitor (IbSPLTI-a). According to the present invention, a
compound structure model (such as construction through AlphaFold2) of
wild type IbSPLTI-a and RNase3 is analyzed, and the IbSPLTI-a is modified by using a protein
directed evolution strategy, particularly by using a hotspot
amino acid scanning and
protein surface design strategy, such that the high-
activity inhibition mutant (such as IbSPLTI-a-m0805) is successfully created and screened; in-vivo and in-vitro function
verification shows that the binding affinity of the mutant (such as IbSPLTI-a-m0805) and SPCSV-RNase 3 is remarkably enhanced, and the mutant shows a
virus accumulation inhibition effect superior to that of a
wild type IbSPLTI-a. The invention also provides a
nucleic acid sequence for coding the mutant, a
plant expression vector containing the sequence, and a method for culturing an anti-SPVD transgenic plant (especially sweet potato) by using the mutant. The invention provides a
core gene resource and a technical path for genetic improvement of SPVD and development of a novel
antiviral protein preparation.