This breakthrough not only
applies to plants but surely to animals.
As shown already with plants, it leads clearly to usable therapies.
A virus is a genetic modifier and
that is why it works. Here identifying
the targeted gene code allows the virus to be thwarted or at least bypassed.
Even better, it can all be done without
impacting on the rest of the gene’s actuvity.
This will surely lead to a flood
of working protocols in medicine in particular and will possibly eliminate or
control mosaic virus problems in plants.
Since plenty of viable varieties
have been eliminated by this problem in the past, we may see restoration of a
wide range of heirloom plants.
Major breakthrough on how viruses infect plants
by Staff Writers
CSIRO plant scientists have shed light on a problem that has puzzled
researchers since the first virus was discovered in 1892 - how exactly do they cause disease?
14 July 2011 In a major breakthrough that helps us better understand how
viruses cause diseases in plants - and potentially in animals and humans - Dr
Ming-Bo Wang and Neil Smith of CSIRO Plant Industry have revealed a genetic
mechanism that enables viral organisms to infect hosts and cause diseases.
"Cucumber Mosaic Virus (CMV) is a common, destructive virus that
affects a wide range of food crops and ornamental plants," Dr Wang said.
"What we found was that CMV, accompanied by a special type of
viral particle called a 'satellite', causes its distinctive yellowing
symptoms in plants by slicing a gene that makes chlorophyll, the green pigment
in leaves. By preventing the production of chlorophyll, the virus causes the
leaves to become partially or entirely yellowed which dramatically affects
growth and productivity."
Importantly, Dr Wang and Mr Smith determined the exact gene affected by
this virus - a gene called CHL1.
"Pinpointing this gene represents a major step forward in
understanding exactly how some viruses cause disease symptoms in susceptible
organisms," Dr Wang said.
Until recently, scientists did not fully understand why viruses only
affected a small range of host organisms. This discovery shows that the
accompanying satellite gene of CMV must directly match the host plant's genes
to cause the yellowing disease.
When the viral satellite's genes match the host plant's genes, the
satellite genes 'lock' onto and slice the host's genes, preventing the host
from forming green chlorophyll pigment.
"Think of it as like doing up a zipper on your jacket - two
opposing but different sections have to come together for it to work," Dr
Wang said.
"So one half of the 'zipper' genes come from the virus and the
other half of the genes from the host, and when they match up the virus causes
disease."
This finding means researchers can focus on finding genes in viruses
that match known genetic sequences in plants, and this can help to reveal the
cause of diseases by other viruses.
Knowing how CMV causes symptoms, Dr Wang and Mr Smith also
experimented to see if they could block the viral disease in plants. They
created specially altered plants with an extra copy of the
chlorophyll-producing gene. This gene had been changed so that it no longer
matched the viral gene, allowing the plants to produce the green chlorophyll
pigment.
Remarkably, this small change in genetic makeup prevented the plants
from becoming yellow and diseased but did not change any other aspects of the
plants' growth, habit or form.
This research was funded by CSIRO and the Australian Research Council
(ARC) and will be presented at the International Botanical Congress in Melbourne
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