Generation of attenuated Passiflora mottle virus through modification of the helper component-protease for cross protection

• Published in: Phytopathology Vol. 113; no. 8; pp. 1605 - 1614
• Main Authors: Do, Duy-Hung, Nguyen, Thi-Bich-Ngoc, Ha, Viet-Cuong, Raja, Joseph A J, Yeh, Shyi-Dong
• Format: Journal Article
• Language: English
• Published: United States 01.08.2023
• Subjects: Virology
• ISSN: 0031-949X; 1943-7684
• DOI: 10.1094/PHYTO-01-23-0007-R

Passiflora mottle virus (PaMoV), an aphid-borne potyvirus, is the primary causal virus of the devastating passionfruit woodiness disease in Vietnam. Here we generated a non-pathogenic, attenuated PaMoV strain for disease control by cross protection. A full-length genomic cDNA of PaMoV strain DN4 from Vietnam was constructed to generate an infectious clone. The green fluorescent protein was tagged at the N-terminal region of the coat protein gene to monitor in planta the severe PaMoV-DN4. Two amino acids within the conserved motifs of HC-Pro of PaMoV-DN4 were mutated individually or in combination as K E or/and R I. Mutants PaMoV-E and PaMoV-I induced local lesions in plants, while PaMoV-E I caused infection without apparent symptoms. In passionfruit plants, PaMoV-E elicited severe leaf mosaic, PaMoV-I induced leaf mottling, while PaMoV-E I caused transient mottling followed by symptomless recovery. PaMoV- E I was stable after six serial passages in yellow passionfruit plants. Its temporal accumulation levels were lower than those of the wild type, with a zigzag accumulation pattern, typical of a beneficial protective virus. An RNA silencing suppression (RSS) assay revealed that all three mutated HC-Pros are defective in RSS. Triplicated cross-protection experiments with a total of 45 plants showed that the attenuated mutant PaMoV-E I provided a high protection rate (91%) against the homologous wild-type virus in passionfruit plants. This work revealed that PaMoV-E I can be used as a protective virus to control PaMoV by cross protection.