1. SEJARAH VIROLOGI TUMBUHAN
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SEJARAH VIROLOGI TUMBUHAN

2. Tulipomania – late 16th century
Before it was known to be caused by a virus, tulips with color breaking symptoms were prized and traded for large sums of goods – this led to “tulipomania” in the late 1500’s
Traded for 1 Viceroy tulip bulb:
4 tons of wheat
8 tons of rye
4 fat oxen
8 fat pigs
12 fat sheep
2 hogsheads of wine
4 barrels of beer
2 barrels of butter
1000 lbs of cheese
1 bed with accessories
1 full dress suit
1 silver goblet

3. Adolf Mayer –1886 – showed that Tobacco mosaic virus was transmissible, could not find bacteria or fungi associated with disease
TMV

4. Dmitri Ivanowski – showed that Tobacco mosaic virus was not retained by filters that retained all bacteria known at that time

5. Martinus Beijerinck – repeated demonstration that Tobacco mosaic virus was not retained by filters that retained all bacteria known at that time
Believed results
Did extensive dilution experiments
Showed diffusion of infectious agent through agar
Named “contagium vivum fluidum”, later virus

6. Wendell Stanley – 1935 At Rockefeller Foundation in Princeton
Crystallized TMV, thought it was only protein
TMV
Stanley Hall, U.C. Berkeley

7. Bawden and Pirie
Crystallized Tomato bushy stunt virus (TBSV); find that it and TMV contain phosphorous – conclude that it is not a protein, but is a nucleoprotein
TMV
TBSV

8. Markham and Smith
Two classes of particles in purified Turnip yellow mosaic virus preparations:
light ones containing only protein, which were not infectious
heavy ones containing protein+nucleic acid, which were infectious
empty
full

9. Myron Brakke - 1951 Development of density gradient centrifugation
Isopycnic: particles reach position of equal density in gradient
Rate-zonal: Particles sediment differentially through medium as a function of size, shape, and density
Equilibrium zonal: Combination of the above

10. Fraenkel-Conrat 1955-1956 Virus Aa: protein
RNA A
capsid a
protein
Complete, infectious TMV particles can be reconstituted in vitro from the RNA and protein components
RNA alone is infectious
RNA can be “transcapsidated” in protein from closely related virus; resulting virus has properties of RNA strain
RNA
reconstitute
in vitro
inoculate plants
symptoms (A)
extract virus
virus Aa

11. Crick and Watson – 1956
TMV virions are composed of one nucleic acid and many identical protein subunits: RNA does not have the coding capacity to make many different subunits

12. Casper and Klug – 1962
Structure of Tomato bushy stunt virus solved by X-ray crystallography, the first icosahedral virus so determined

13. Heinz Sanger – 1978 Complete sequence of Potato spindle tuber viroid
First pathogen sequence to be determined
Yielded relatively little information that was immediately useful
1 cggaactaaa ctcgtggttc ctgtggttca cacctgacct cctgagcaaa aaagaaaaaa gataggcggc tcggaggagc gcttcaggga tccccgggga aacctggagc gaactggcaa aaaaggacgg tggggagtgc ccagcggccg acaggagtaa ttcccgccga aacagggttt tcacccttcc tttcttcggg tgtccttcct cgcgcccgca ggaccacccc tcgccccctt tgcgctgtcg cttcggctac tacccggtgg aaacaactga agctcccgag aaccgctttt tctctatctt cttgcttccg gggcgagggt gtttagccct tggaaccgca gttggttcct 359

14. Paul Ahlquist – 1984
Infectious viral RNA transcribed in vitro from cDNA clones
Done with Brome mosaic virus – with 3 RNAs
Brought reverse genetics to RNA viruses
RNA
Inoculate plants
RNA
cDNA

15. Roger Beachy – 1986
Transgenic plants expressing TMV coat protein are resistant to virus infection
First example of “pathogen-mediated resistance”

16. Bill Dougherty – 1991
RNA was critical component in resistance in pathogen-mediated resistance
All of the hallmarks that later came to be associated with PTGS and RNAi were first observed with Tobacco etch virus (TEV) (1993 Lindbo et al., Plant Cell 5: )