Plant and animal viruse

A
SEMINAR
ON
PLANT AND ANIMAL VIRUSES
PROF. J.P. SHARMA (DIRECTOR)
DR. R.K. RAO (PRINCIPAL)
GUIDED BY - RACHANA TIWARI
PRESENTED BY..
NIKITA DEWANGAN
M.Sc.1st SEM
BIOTECHNOLOGY
G.D. RUNGTA COLLEGE OF SCIENCE & TECHNOLOGY
KOHKA-KURUD,BHILAI DURG (C.G.)

 INTRODUCTION
 HISTORY
 MORPHOLOGY OF VIRUSES
 PLANT VIRUS
 TOBACCO MOSAIC VIRUS (TMV)
 SYMPTOMS
 VIRUS STRUCTURE
 PROTEIN SYNTHESIS
 TRANSMISSION
 MODE OF ACTION
 EFFECT OFVIRUS ON PLANT
 ANIMAL VIRUS
 CLASSIFICATION
 DNA CONTAINING - SV 40 VIRUS
 RNA CONTAINING - RHABDOVIRUS
 CONCLUSION
 REFRENCES
PLANT AND ANIMAL VIRUS
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INTRODUCTION
 Viruses are small obligate intracellular parasites which by definition contain
either a RNA a or DNA genome , surrounded by a protective virus – coded
protein coat.
HISTORY
 Edward Jenner (1798) introduced the term virus in microbiology.
 Virus Greek means ‘’ poison’’.
 In 1892 for the first time a Russian botanist DMITRI IWANOWSKI discover
the virus.
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SHAPE - Viruses are of different shapes such as spherical or cuboid ( adenovirus) ,
elongated (potato viruses), flexuous or coiled (beet yellow), bullet shaped (rabies
virus), filamentous ( bacteriophages M13) , pleomorphic.
SIZE - Variable size from 20 nm to 300 nm in diameter.
• They are smallest than bacteria, some are slightly larger than protein and nucleic
acid molecules and some are about of the same size ( small pox virus) as the
smallest bacterium and some virus slightly large (300 – 400 nm).
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1. HELICAL ( CYLINDRICAL) VIRUSES -
 The helical viruses are elongated, rod shaped, rigid or flexible.
 There capsid is a hollow cylinder with a helical structure.
 Capsid cosists of monomers arranged helically in rotational axis.
 The consist may be naked e.g. TMV or envelope e.g. influenza virus.
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4Fig ; - 1 ,structure of helical virus

2. POLYHEDRAL ( ICOSAHEDRAL)
VIRUSES -
 Polyhedral structure has the three possible
symmetries such as tetrahedral, octahedral and
icosahedral.
 The viruses are more or less spherical, therefore
icosahedral symmetry is the best one for
packaging and bonding of subunits.
 The capsomers of each face form an equatorial
triangles and 12 intersepting point or corners.
 They consist naked capsid e.g. adenovirus or
envelope e.g. herpes simplex virus.
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Fig ; 2 , structure of
polyhedral virus

3. COMPLEX VIRUSES
-
• The viruses which have
the unidentifiable
capsids or have the
capsids with additional
structures are called
complex viruses.
• Capsids not clearly
identified e.g. vaccinia
virus etc.
• Capsids to which some
other structure are
attached e.g. some
bacteriophages etc.
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Fig ; - 3 structure of complex virus

 ENVELOPE -
• There are certain plant and animal viruses and bacteriophage both icosahedral and
helical , which are surrounded by a thin membranous envelope. This envelope is
about 10-15 µm thick . it us made up of protein , lipids and carbohydrates.
• Which are combined to form glycoprotein and lipoprotein.
• Lipids provide flexibility to the shape , therefore viruses look of variable size and
shape.
• Protein component of the envelope is of viral origin and lipid and carbohydrate may
be the feature of host membrane.
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• Plant viruses are viruses that affect plants like all other viruses plant
viruses are obligate intracellular parasites that do not have the molecular
machinery to replicate without a pathogenic to higher plants.
• Example ; - tobacco mosaic virus.
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INTRODUCTION
• TMV is the most serious pathogen causing mosaic on tobacco leaves.
• It is transmitted by artificial inoculation but not by insect vectors.
• TMV is the most resistant virus known so far of which the thermal death point is 90 ºc
for 10 minutes.
• This is the first virus that was crystallized in 1935 by W.M. STANLEY in the U.S.A.
SYMPTOMS
• TMV damages the salanaceous plants. However, it can infect theother plant too.
• After infection, it developes symptoms of lightning of leaf colour along the veins in early
stages.
• There after it turns into light and dark green mosaic symptoms.
• Along the veins green colour turns into dark green and the internal region turns into
chlorotic.
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• Some times dark green blisters appear in the leaf blade.
• The virus reduces the yield as well as quality of the products.
VIRUS STRUCTURE
• Franklin et al (1957) have described the structure of TMV.
• It is rod shaped helical virus measuring about 280µm with a molecular weight of
396 daltons.
• The virion is made up of 2130 protein subunit of identical size.
• The protein subunits are arranged around a central hole of 4nm (40 Å).
• Each protein subunit is made up of a single polypeptide chain which possesses
158 amino acids the molecular weight 17500 daltons.
• Inside the protein capsid there is a single stranded RNA molecule which is also
spirally coiled to form helix.
• Virus RNA consists of 6500 nucleotides.
• In one turn the RNA contain 49 nucleotides.
• Total numbers of protein subunit counting in three turns is 49.
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PROTEIN SYNTHESIS
• The virus RNA utilizes the amino acids ribosomes and tRNA of the host and
synthesizes the complementary strand and protein i.e. coat proteins of 17500daltons
and two other polypeptides.
• The ratio of nucleic acid and protein differs with each virus.
• Nucleic acid is about 5-40% of the virus and protein 60-70%.
• Each protein subunit of TMV consists of 158 amino acid making a total number to
about 17531.
TRANSMISSION
• TMV is transmitted through the cell sap of host and enters a new host through wound
incision.
• Wound is caused in plant due to various cultural operations such as clipping or
topping the shoot.
• It is also transmitted by wind and water.
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fig;4, structure of tobacco mosaic virus
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MODE OF ACTION
• In the cell the tobacco mosaic virus form crystals in the chloroplast and accumulate.
• Resulting pigment of cell which produces colour get affected, colour may turn to
colour less.

1 . EXTERNAL SYMPTOMS :-
a. MOSAIC - Development of light (chlorosis) and dark green area on leaves are due
to disturbances of chloroplast and decrease in chlorophyll content.
b. CHLOROSIS , VEIN CLEARING AND VEIN BANDING - Vein clearing
symptoms develop adjacent to veins before chlorosis of tissue. While broader bands
of green tissue in chlorosis or necrosis is called vein banding.
c. RINGSPOT - Ringspot is characterized by formation of concentric rings or
broken rings of infected dead cells. The ringspot may be chlorotic rings rather than
necrotic rings.
d. NECROSIS - Besides localized cell death in necrotic local lesion or ringspots ,
necrosis in certain areas organs e.g. leaves, fruits, seeds , tubes or entire plant.
Affected leaves shows scattered necrotic patches of dead tissue.
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e. LEAF ABNORMALITIES - Due to virus infection leaves show abnormal growth
like leaf curling, leaf rolling, crinkling, puckering (depression)etc. the other
abnormalities may also develop in leaves such as smaller blistered and thickened
leaves.
f. FLOWER SYMPTOMS - The colour breaking means streaks or sector of tissue
with such colour that are different from the normal one. This happens due to loss or
increase of anthocyanin pigment in petals.
2. INTERNAL SYMPTOMS
a. HISTOLOGICALABNORMALITIES -
In leaves showing mosaic symptoms. Mesophyl cells are smaller and less
differentiated.
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b.CYTOLOGICALABNOMALITIES -
• Many cytological abnormalities are seen when virus infected cell are studied
cytologically. Moreover some viruses affect specific arganelles only.
• Tymovirus induces formation of marginal verticles in chloroplasts. Tobacco rattle
virus modifies mitochondria and aggregates to form inclusion bodies.
• TMV particles are found in cytoplasm where as TMV of strain U5 are round in
chloroplasdt and nuclei.
• Chloroplasts may be rounded swollen and clumped together in the cells . chloroplast
may be fragmented and colour may turn to colour less.
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CLASSIFICATION - On the basis of types of nucleic acid the classification of
viruses are as :-
 Class 1. dsDNA viruses
• Adenoviruses genome size 35-40 kb.
• Herpes virus genome size 120- 200 kb.
• Papovavirus genome size 5-8 kb.
• Pox virus genome size 120-300 kb.
 Class 2. ssDNA viruses
• Parvovirus genome size 4-5kb.
 Class 3. (+) ss RNA viruses
• Coranavirus genome size 16-21 kb.
• Picorna virus genome size 7 kb.
• Togavirus genome size 17 kb.
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 Class 4. (-) ssRNA viruses
• Paramyxoviruses genome size 15 kb.
• Rhabdovirus genome size 12- 1 kb.
• Orthomyxovirus genome size 14 kb.
 Class 5. dsRNA viruses
• Reovirus genome size 18-30 kb.
 Class 6. RNA – DNA viruses
• In these viruses (+) ssRNA direct synthesia of (-) DNA which in turn acts as template
for the transcription of mRNA .
• Retrovirus genome 7-10 kb.
 Class 7. DNA- RNA viruses
• This group consists of DNA containing hepatitis B viruses.
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 The DNA containing animal virus : - SV40 virus
• SV40 is an oncogenic virus.
• It is naked and icosahedral in morphology with a diameter of 45nm.
• Capsid consists of 72 capsomeres.
• SV40 is similar to polyoma virus in size and structure.
• Polyoma is associated with tumour in mice.
 REPLICATION
• Virus enters the cell and directly migrats to the nucleus and then mutation cause in
genetic material of host resulting normal activity of cell inhibit which causes tumor.
• Replication of viral RNA takes place inside the nucleus.
• Before the replication begins early proteins are synthesized in the nucleus of the
infected cells.
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• The ds- DNA in its native form is supercoiled ( i.e. covalently closed circle ) . helix
having the sedimentation coefficient of 215.
• Total G+C content of acid is 41%.
• After breaking the phosphodiester bond single stranded DNA helix is converted into a
relaxed circular form.
• This form has the sedimentation coefficient of 165. A linear form ( of 145) is formed
after double stranded break in the supercoil.
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Fig ; 5, SV40 virus structure

 The RNA containing virus :- Rhabdovirus
• Rhabdovirus are bullet shaped with one flattened end.
• Rhabdo is a Greek word which means a rod but the term rod is not accurate to its
morphology.
• Rhabdoviruses are found in vertebrates, invertebrates and plant.
• The example of rhabdovirus are rabies virus, vesicular stromatitis virus (VSV) and potato
yellow dwaef virus.
• VSV is the most extensively studied rhabdovirus.
• It is a mild pathogen to cattle. . Vesicular stromatitis virus affect the central nervous
system so host parasite do abnormal behavior.
• VSV contain a nucleocapsid (70 – 180) which is envelope on its outer surface, consists of
numerous spikes of glycoprotein on inner surface and the membrane (M) protain.
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Fig; 6, structure of Rhabdovirus
• Inside the nucleocapsid, there is a (-) ssRNA molecule which is cylindrically coiled to
make the core hollow.
• The RNA polymerase uses (-) RNA strand as the template and produce (+) RNA strand.
• The (+) RNA strand acts as mRNA and as a template for the synthesis of viral RNA.

• It is concluded that a virus is a non- cellualar particle made up to genetic
material and protein that can invade living cell.
• Virus can replicate its genetic material in the host cell.
• Virus can naked as well as have envelope.
• Virus can infect all type of life – animal , plant , human and cause diseases.
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R. C. DUBEY 2006 MICROBIOLOGY
SOME CONTENT FROM NET : -
 www.ncbi.nlm.nih.gov/books/NBK8174/virus
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