Download Plant viruses are often spread from plant to plant by

Plant viruses are often spread from plant to plant by organisms known
as vectors.
LEARNING OBJECTIVE [ edit ]
Outline plant virus life cycles
KEY POINTS [ edit ]
Plant viruses are harmless to humans and other animals because they can only reproduce in
living plant cells.
For the virus to reproduce and thereby establish infection, itmust enter cells of
the host organism and use those cells' materials.
A virus must take control of the host cell's replicationmechanisms. At this stage a distinction
between susceptibility and permissibility of a host cell is made.
After control is established and the environment is set for the virus to begin making copies of
itself, replication occurs quickly by the millions.
TERM [ edit ]
vector
A carrier of a disease-causing agent.
EXAMPLE [ edit ]
Tobacco mosaic virus (TMV) and Cauliflower mosaic virus (CaMV) are frequently used in plant
molecular biology. Of special interest is the CaMV 35S promoter, which is a very strong promoter
most frequently used in plant transformations.
Give us feedback on this content: FULL TEXT [edit ]
Plant viruses are viruses that affect plants. Like all other viruses, plant viruses
areobligateintracellularparasites that do
not have the molecular machinery to
replicate without a host. Plant viruses
are pathogenic to higher plants.
There are many types of plant virus, but
often they only cause a loss of yield, and it
is not economically viable to try to control
them. Plant viruses are often spread from
plant to plant by organisms (vectors).
These are normally insects, but some
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fungi,nematode worms and single-celled
organisms have been shown to be vectors. When control of plant virus infections is
considered economical, (for perennial fruits for example), efforts are concentrated on killing
the vectors and removing alternate hosts such as weeds. Plant viruses are harmless to
humans and other animals because they can only reproduce in living plant cells.
Viral Life Cycle
For the virus to reproduce and thereby establish infection, it must enter cells of the host
organism and use those cells' materials. To enter the cells, proteins on the surface of the virus
interact with proteins of the cell. Attachment, or adsorption, occurs between the viral particle
and the host cell membrane. A hole forms in the cell membrane, then the virus particle or
itsgenetic contents are released into the host cell, where viral reproduction may commence.
Next, a virus must take control of the host cell's replication mechanisms. At this stage, a
distinction between susceptibility and permissibility of a host cell is made. Permissibility
determines the outcome of the infection. After control is established and the environment is
set for the virus to begin making copies of itself, replication occurs quickly by the millions.
After a virus has made many copies of itself, it usually has exhausted the cell of its resources.
The host cell is now no longer useful to the virus, therefore the cell often dies and the newly
produced viruses must find a new host. The process by which virus progeny are released to
find new hosts, is called shedding. This is the final stage in the viral life cycle. Some viruses
can "hide" within a cell, either to evade the host cell defenses or immune system, or simply
because it is not in the best interest of the virus to continually replicate. This hiding is
deemed latency. During this time, the virus does not produce any progeny, it remains inactive
until external stimuli—such as light or stress—prompts it to activate.
Viruses can be spread by direct transfer of sap, and by contact of a wounded plant with a
healthy one. Such contact may occur during agricultural practices, when damage is caused by
tools or hands, or naturally, when an animal feeds on the plant. Generally Tobacco mosaic
virus (TMV), potato viruses, and cucumber mosaic viruses are transmitted via sap.
Tobacco mosaic virus and Cauliflower mosaic virus (CaMV) are frequently used in plant
molecular biology. Of special interest is the CaMV 35S promoter, which is a very strong
promoter most frequently used in plant transformations.
Tobacco Mosaic Virus
Tobacco mosaic virus (TMV) is a positive­sense single stranded RNA virus that infects plants,
especially tobacco and other members of the family Solanaceae. The infection causes characteristic
patterns (mottling and discoloration) on the leaves (hence the name). TMV was the first virus to be
discovered. Although it was known from the late 19th century that an infectious disease was
damaging tobacco crops, it was not until 1930 that the infectious agent was determined to be a
virus.