Detail introduction about plant virology

1. LANDMARKS IN THE
DEVELOPMENT OF VIROLOGY
N. H. SHANKAR REDDY
PH.D., PLANT PATHOLOGY
ANNAMALAI UNIVERSITY

2. 16th century –
 Tulipomania – Tulip bulbs introduced form Netherland produced
‘broken colour flower with variegations’ have great demand and
expand market value with great extent in short period, leading to
increase of tulip prizes unimaginably.
 Later days it was discovered that it was caused by potyvirus
group and are transmitted by aphids.

3. 1886 – Adolf Mayer (Germany)-
• Coined the term ‘Mosaic’
• First to prove the transmissible plant virus i.e. TMV
• He called sap transmission of tobacco disease is
‘Mosaikkrankheit’
• Later he performed experiments with Chamber land filter paper,
even though the virus retains infectivity.
• He thought that the causal agent of mosaic disease of tobacco was
due to the bacteria.

4. 1892 – D. Ivanovsky (Russia) –
• Proved that the causal agent of tobacco mosaic disease could
pass through bacteria proof filters.
• Concluded that the causal agent of tobacco mosaic (virus) is
smaller than bacteria.
• 1st man who discovered ‘inclusion bodies’
• Described the horizontal transmission of plant viruses

5. 1898 – Beijerinck –
• Dutch microbiologist and botanist.
• Founder and Father of Virology / Father of Environmental
Ecology
• Performed agar diffusion experiments and coined the term ‘Virus’
• He called the liquid material of virus is “Contagium vivum
fluidum” which cause the repeated infection in Tobacco mosaic
virus
• The first known sulfate-reducing bacterium, was isolated and
described by Beijerinck (Spirillum desulfuricans, now called
as Desulfovibrio desulfuricans)
• Clostridium beijerinckii is a gram positive, rod
shaped; motile bacterium was named after Beijerinck.

6. 1915 – Twort, 1917 -F. D. Herelle – Individually discovered bacteriophages
1929 – Holmes – Developed local lesion assay in Nicotiana glutinosa
• (Local lesion assay - A tool by which virus could be measured by showing that the
amount of virus present in the plant sap preparation is proportional to the number of
lesions produced on appropriate host plant leaves rubbed with the sap)
• Observed that single dominant gene controlling the hypersensitive reaction (HR) and
proposed the “viral hypersensitivity”. Single dominant gene subsequently transferred
from N. glutinosa to N. tabacum in which the TMV resistant cultivars are produced

7. 1929 – Mckinney –
• Developed cross protection/ pre-immunization technique for control of citrus tristeza
virus (CTV)
• Cross protection was 1st used against TMV
1931-1933 - Knoll and Ruska-
• The first prototype of electron microscope was
developed by Ernst Ruska (1931) and Knoll which is
capable of 400 magnification power
• Then, Ruska (1933) built the first electron microscope
that attains high resolution with an optical (light)
microscope.
• He won the Nobel Prize in Physics in 1986 for his
fundamental work in electron optics, including the
design of the first electron microscope.

8. 1931 - K. M. Smith –
 Used indicator plant in viral studies was taught by him
 Separation of Potato viruses and named as X and Y.
 Authored a text book “Plant Virus Diseases” in 1937
 He named and grouped viruses according to the generic name of the host.
1933 - Martin Schlesinger –
 Hungarian chemist
 Separated and purified bacteriophages by the technique of ultracentrifugation and
concluded that it contains equal amount of proteins and DNA

9. 1935- W. M. Stanley –
• American biochemist, virologist
• Done Purification/ Crystallisation of virus (by using
ammonium sulphate)
(Preparation of enzymes and virus proteins in a pure form)
• He received Nobel Prize in 1946 (for crystallisation of virus)
• He believed that virus was an autocatalytic protein that could
multiply with in the living cell
• Molecular plant pathology work can be initiated with W. M.
Stanley work
• (Note - X-ray diffraction studies by J.D. Bernal and I.
Fankuchen showed that they are true three dimensional crystals,
they were paracrystalline and that the rod like virus particles.

10. 1936 – F. E. Bawden and N. W. Pirie –
• Demonstrated that virus is a nucleoprotein which consists both nucleic acid and protein
• They also purified/ crystallised TMV in 1936 (after W. M. Stanley experiment), further
purification of protein in neutral aqueous solution can be obtained in liquid crystalline
states.
• First suggested that virus replication might be analogous to the synthesis of cellular
components (1936)
• Detect that phosphate is inherent part in RNA molecule.
• Their studies reveals that 1-2gm of protein can be isolated from a litre of sap, it depends
based on the age of the plant and duration of infection

11. Luria and Delbruck –
 Discovered ‘bacterial mutation’
 Considered as founding fathers of phage genetics
 Received Nobel prize in Physiology and medicine in
1969
 Also worked on replication mechanism and genetic
structure of viruses
 Delbruck alone discovered ‘mutation in virus’ in
1939

12. 1952- 1953 – Watson and Crick –
• Discovered the double helical structure of DNA, in which their
discovery revolutionized the entire biology.
• They contended that all viruses must be built up symmetrically
from identical protein subunits that surround the nucleic acid
in 1956
• General theory of structure of capsid of virus; the coat protein
made up of numerous identical subunits as helicle rods or
spherical shell.
• Got noble prize in physiology and medicine in 1962

13. 1952 – Harshey and Chase –
 Demonstrated the infection behaviour of bacteriophage and showed that only DNA
enters into the host cell and protein remain outside.
 Nucleic acid portion that was responsible for the infectivity and carried the genetic
material.

14. 1956 – Gierrer and Schramm –
• Showed that nucleic acid is the infectious agent
• (Showed that only nucleic acid of TMV is infective and protein coat does not have any
role in infection, Nucleic acids carry hereditary information and that Nucleic acid alone
is sufficient for viral infectivity)
• Also investigated about double standard RNA viruses (ds RNA)

15. 1958 – Hewitt et al – Reported grape fan leaf virus is transmitted by nematode Xiphinema
index, and nematode implicated the transmissions.
1962 – Teakle – 1st transported fungal transmission (Olpidium brassicae) of soil borne
Tobacco necrosis virus
1968 - Shepherd et al - Reported 1st DNA plant viruses, double-stranded DNA (ds DNA) in
cauliflower mosaic virus
1968 – I. Takebe and Y. Ostsuki
 Described a technique for propagating and infecting protoplasts with viruses
 The procedure allowed many detailed studies of viral replication and eventual the
regression of plants from a single cell to protoplasts, which was an important step in
producing transgenic plants.

16. 1975– Kohler and Milstein- Developed “Hybridoma technology” in monoclonal antibodies
production – Nobel prize in 1984.
1976 – Voller et al, 1977 – Clark and Adams – Developed ELISA technique and used
ELISA in Plant virus detection.

17. 1982 – Aaron Klug - For his development of crystallographic electron microscopy and his
structural elucidation of biologically important nucleic acid-protein complexes
1986 – Powel- abel and Beachy –
 Initiated molecular plant pathology work by improving the disease resistance gene.
 Developed 1st transgenic resistance mediated by the CP gene obtained from tobacco
plants against TMV.
 Beachy developed “coat protein mediated gene resistance”.

18. 1984- Prusiner-
• Discovered of Prions in animals:
• Received Nobel Prize in 1997 in physiology of
Medicines for the discovery of ‘Prions’ and biological
principles of infection

19. 1998 - Andrew Fire & Craig Mello –
• First described their work on RNA interference Gene silencing by dsRNA, in the
nematode Caenorhabdatis elegans.
• RNA interference is traditionally/ otherwise called as Post transcriptional gene
silencing (PTGS)
• shared Nobel prize in 2006.

20. 2001 - Li et al – Reported the role of proteins present in the head tissue of aphid vector in the
transmission of the virus- they found two proteins as receptor of BYDV; they act as sensors
and if absent in any aphid no transmission occurs
2003 – P. Lava Kumar at ICRISAT, made a major breakthrough by identifying and
characterizing the virus associated with pigeon pea sterility mosaic and reported that, it is
transmitted by Eriophyid mite. He was honoured with the young scientist award of the
Consultative Group on International Agricultural Research (CGIAR) for this achievement

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