Do Duy-Hung, Nguyen Thi-Bich-Ngoc, Ha Viet-Cuong, Raja Joseph A J, Yeh Shyi-Dong
Department of Plant Pathology, National Chung Hsing University, Taichung, Taiwan, R.O.C.
Plant Pathology Division, Plant Protection Research Institute, Hanoi, Vietnam.
Phytopathology. 2023 Aug;113(8):1605-1614. doi: 10.1094/PHYTO-01-23-0007-R. Epub 2023 Sep 26.
Passiflora mottle virus (PaMoV), an aphid-borne potyvirus, is the primary causal virus of devastating passionfruit woodiness disease in Vietnam. Here we generated a nonpathogenic, 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 helper component protease (HC-Pro) of PaMoV-DN4 were mutated individually or in combination as KE or/and RI. Mutants PaMoV-E and PaMoV-I induced local lesions in plants, while PaMoV-EI caused infection without apparent symptoms. In passionfruit () plants, PaMoV-E elicited severe leaf mosaic and PaMoV-I induced leaf mottling, while PaMoV-EI caused transient mottling followed by symptomless recovery. PaMoV-EI was stable after six serial passages in yellow passionfruit ( f. ) 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-EI provided a high protection rate (91%) against the homologous wild-type virus in passionfruit plants. This work revealed that PaMoV-EI can be used as a protective virus to control PaMoV by cross protection.
西番莲斑驳病毒（PaMoV）是一种由蚜虫传播的马铃薯Y病毒属病毒，是越南毁灭性西番莲木质化病的主要致病病毒。在此，我们通过交叉保护产生了一种用于疾病控制的非致病性减毒PaMoV株系。构建了来自越南的PaMoV株系DN4的全长基因组cDNA以产生感染性克隆。在外壳蛋白基因的N端区域标记绿色荧光蛋白，以在植物体内监测强毒株PaMoV-DN4。将PaMoV-DN4辅助成分蛋白酶（HC-Pro）保守基序内的两个氨基酸分别或组合突变为KE或/和RI。突变体PaMoV-E和PaMoV-I在植物中诱导局部病斑，而PaMoV-EI引起无明显症状的感染。在西番莲（）植株中，PaMoV-E引发严重的叶片花叶病，PaMoV-I诱导叶片斑驳，而PaMoV-EI引起短暂斑驳，随后无症状恢复。PaMoV-EI在黄果西番莲（f.）植株中连续传代六次后稳定。其瞬时积累水平低于野生型，呈锯齿状积累模式，这是有益保护病毒的典型特征。RNA沉默抑制（RSS）试验表明，所有三种突变的HC-Pro在RSS方面均有缺陷。对总共45株植物进行的三次重复交叉保护试验表明，减毒突变体PaMoV-EI在西番莲植株中对同源野生型病毒提供了高保护率（91%）。这项工作表明，PaMoV-EI可用作保护病毒，通过交叉保护来控制PaMoV。
