Journal of General Virology (2004) 85, 3421-3430

Boaz Kimalov, Amit Gal-On, Ran Stav, Eduard Belausov and Tzahi Arazi (2004)
Maintenance of coat protein N-terminal net charge and not primary sequence is essential for Zucchini yellow mosaic virus systemic infectivity
Journal of General Virology 85 (11), 3421-3430
Abstract: Zucchini yellow mosaic virus (ZYMV) surface exposed coat protein (CP) N-terminal domain (Nt) is 43 aa long and contains an equal number of positively and negatively charged amino acid residues (CP-Nt net charge=0). A ZYMV-AGII truncation mutant lacking the first 20 aa of its CP-Nt (AGII-CP-Delta-20; CP-Nt net charge=+2) was found to be systemically non-infectious even though AGII mutants harbouring larger CP-Nt deletions were previously demonstrated to be fully infectious. Nevertheless, AGII-CP-Delta-20 infectivity was restored by fusion to its CP-Nt two Asp residues or a negatively charged Myc peptide, both predicted to neutralize CP-Nt net positive charge. To evaluate further the significance of CP-Nt net charge for AGII infectivity, a series of CP-Nt net charge mutants was generated and analysed for systemic infectivity of squash plants. AGII-CP^KKK harbouring a CP-Nt amino fusion of three Lys residues (CP-Nt net charge=+3) was not systemically infectious. Addition of up to four Asp residues to CP-Nt did not abolish virus infectivity, although certain mutants were genetically unstable and had delayed infectivity. Addition of five negatively charged residues abolished infectivity (AGII-CP^DDDDD; CP-Nt net charge=-5) even though a recombinant CP^DDDDD could assemble into potyviral-like particle in bacteria. Neutralization of CP-Nt net charge by fusing Asp or Lys residues recovered infectivity of AGII-CP^KKK and AGII-CP^DDDDD. GFP-tagging of these mutants has demonstrated that both viruses have defective cell-to-cell movement. Together, these findings suggest that maintenance of CP-Nt net charge and not primary sequence is essential for ZYMV infectivity.
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Database assignments for author(s): Tzahi Arazi, Amit Gal-On

Research topic(s) for pests/diseases/weeds:
molecular biology - genes

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Zucchini yellow mosaic virus