PVY, potyviruses


Lopez-Moya, J.J., and Garcia, J.A. Potyviruses in Encyclopedia of Virology, 2nd ed pp 1369-1375, Ed. R.G. Webster (1999)
Maia, I. G., Haenni, A-L., and Bernardi, F. Potyviral HC-Pro: a multifunctional protein. J. Gen. Virol. 77 , 1335-41 (1996)
Pirone, T.P., Blanc, S. Helper-dependent vector transmission of plant viruses Ann. Rev. Phytopath. 34, 227-47 (1996).
Revers, F., LeGall, O., Candresse, T. and Maule, A.J. New advances in understanding of the molecular biology of plant/potyvirus interactions. Mol. Plant Microbe Interactions 12, 367-76 (1999)
Riechmann, R.L., Lain, S., Garcia, J.A. Highlights and prospects of potyvirus molecular biology. J. Gen. Virol. 73, 1-16 (1992)
Shukla, D.D., Ward, C.W., and Brunt, A.A. The potyviridae. CAB International. (1994) (QR411.S48)
Urcuqui-Inchima S., Haenni A.L., Bernardi F. Potyvirus proteins: a wealth of functions. Virus Res 74, 157-175 (2001)
Wang, R.Y., Powell, G., Hardie, and Pirone, T.P. Role of the helper component in vector-specific transmission of potyviruses. J. Gen. Virol. 79, 1519-24 (1998)


I- General properties - major group with many important disease agents
1- Filaments, 680-900nm in length, 12-15nm in diameter (distinctive by EM)
2- ssRNA, about 10kb
3- Host ranges generally narrow, but sometimes broad host ranges
4-Cytoplasmic (pinwheel) inclusion protein (found in all potyviridae)
5-Nuclear inclusion protein (not in all viruses)
6-Amorphous inclusion
II- Vectors of genus (superfamily) Potyviridae
1- Potyviruses are aphid transmitted (nonpersistent), often seed transmitted
2- Rymoviruses, tritimoviruses transmitted by mites
3- Ipomoviruses, 900nm in length, transmitted by whiteflies
4- Bymoviruses, two components, transmitted by soil fungi
a- RNA1, analogous to 3' end of potyviruses
b- RNA2, analogous to P1, HC-Pro (5' end of potyviruses)
III- Genome strategy
1- VPg (genome linked protein) at 5' end
2- Poly A at 3' end
3- Translated as a polyprotein with capsid protein at 3' end
4- P1 (Binds RNA, has protease activity)
5- HC-Pro (Vector transmission, protease, systemic movement)
6- P3 (component of cytoplasmic inclusion)
7- 6k protein (membrane binding)
8- CI inclusion (helicase)
9- 6k protein (membrane binding)
10- NIa = Vpg-protease
a- Carries out most proteolytic cleavages
b- Transport into nucleus requires specific sequences
c- Nuclear transport can be followed by reporter gene (Gus fusion)
d- Vpg binds to translation initiation factor
11- NIb = RNA polymerase
12- Capsid protein
IV- Proteolysis
1- P1, single cleavage - removes itself from polyprotein
2- HC-Pro, single cleavage, can't be complement in trans
3- NIa, serine protease analog with cys at active site
a- SMV NIa cleaves (N/E-X-V-X-X-Q||G/S), other NIas cleave similar sequences
b- Cleavage intermediates may be important in virus replication
4- Suboptimal cleavage site within NIa, do products remain in cytoplasm?
V- Capsid protein
1- N and C termini sensitive to proteolysis (protruding "hair")
2- Deletions in N-terminus lose ability to move systemically
3- Central core highly conserved
VI- Aphid transmission - nonpersistent (stylet-borne)
1- Aphids don't transmit purified virus
2- Prefeeding on supernatant restores transmissibility of pure virus
3- Both capsid protein and HC-Pro essential for transmission
4- DAG (amino acid sequence) near N-terminus of capsid important
5- Transmission correlates with binding to aphid stylet
VII- Evolution
1- Nucleotide sequences (especially capsid gene) available for many viruses
2- Some regions of the genome (e.g. P1) vary more than others
3- Viruses differing by less than 10% in sequence considered strains
4- Viruses differing by more than 25% in sequence are different species
5- Viruses transmitted by given type of vector cluster into group(s)

E-mail: llane1@unl.edu