Phytopathology (2000) 90, 467-473

Amit Gal-On (2000)
A point mutation in the FRNK motif of the potyvirus helper component-protease gene alters symptom expression in cucurbits and elicits protection against the severe homologous virus
Phytopathology 90 (5), 467-473
Abstract: Sequence comparison had previously shown three amino acid changes in conserved motifs in the 455-amino acid sequence of the helper component-protease (HC-Pro) between a severe field strain of Zucchini yellow mosaic virus (ZYMV-NAT) and a mild field strain of ZYMV (ZYMV-WK). In this study, exchange of fragments and site-directed mutagenesis within the HC-Pro gene in an infectious clone of ZYMV enabled the effects of the mutations on symptom expression to be mapped. The substitution of Ile for Arg at position 180 in the conserved motif Phe-Arg-Asn-Lys (FRNK) of potyviruses was found to affect symptom expression. Infection of cucurbits with the engineered ZYMV (ZYMV-AG) that contained this mutation caused a dramatic symptom change from severe to mild in squash and to a symptom-free appearance in cucumber, melon, and watermelon. The Ile to Arg mutation was found to be stable, and no revertant virus was found after several passages through plants after long incubation periods. The AG strain was detected 4 days postinoculation and accumulated in cucurbits to a level and with kinetics similar to that of the wild-type ZYMV-AT strain. Cucurbit plants infected with the AG strain were protected against infection by the severe strain.
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Database assignments for author(s): Amit Gal-On

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Zucchini yellow mosaic virus	Cucumber (Cucumis sativus)
	Zucchini yellow mosaic virus	Melon (Cucumis melo)
	Zucchini yellow mosaic virus	Watermelon/colocynth (Citrullus)
	Zucchini yellow mosaic virus	Squash/pumpkin (Cucurbita)