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24-Feb-02.
Method to Obtain Male Sterile Plants Patented
by Aventis
Aventis CropScience N.V. (headquartered in Lyon, France) has been
awarded a patent (#US6344602) for inventing a method to obtain male
sterile plants in otherwise sexually cross-pollinated crop plants
such as canola, corn or rice. Increases in crop production may result
from planting hybrid seeds, but it is an extremely laborious process
and therefore costly to obtain hybrid seeds because of the need
to remove stamens (male reproductive organs) manually. Male-sterile
plants, whether produced naturally or artificially, reduce that
cost. Aventis has used a gene named barnase, derived from
the bacterium Bacillus amyloliguefaciens, to construct male-sterile
lines by expressing a chimeric barnase gene specifically
in male reproductive tissues. The barnase gene encodes an
extracellular ribonuclease. The company also developed a male fertility
restorer line using the barstar gene, also derived from B.
amyloligue- faciens. The protein encoded by barstar inhibits
the activity of barnase. Aventis has developed male-sterile
and male fertility restorer lines using this system in oil
seed rape, corn and rice. To obtain more details, search
for the patent number 6344602 at the US Patent and Trade Office
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Overexpression
of Arabidopsis ESR1 Induces Initiation of Shoot Regeneration
In the December
issue of the Plant Cell (13:2609-2618), N-H Chua and his associates
at the Rockefeller University, New York, report that they have identified
a novel cDNA ESR1 (Enhancer of Shoot Regeneration) by screening
an Arabidopsis cDNA library. Analysis of the ESR1 shows that it
can induce shoot formation in Arabidopsis root explants in the absence
of cytokinin. They also showed that in the presence of the optimum
level of cytokinin concentration, overexpression of ESR1 not only
enhances the shoot generation ability of root explants but its effects
are synergistic. Furthermore, they observed that the overexpression
of ESR1 does neither affect callus induction nor root formation
indicating that it acts only on the shoot formation process. ESR1
encodes a putative transcription factor with an AP2/EREBP domain.
Their results further reveal that cytokinin triggers the expression
of ESR1 in wild-type Arabidopsis plants. They observed a transient
increase of ESR1 transcript levels before shoot formation indicating
that there is a close relationship between enhancement of transcript
levels and the acquisition of competence for shoot regeneration.
According to the authors, the presence of cytokinin in the shoot-inducing
medium may account for a transient increase of ESR1 transcript levels
during shoot regeneration from root explants. Based on their results,
the authors suggest that the induction of shoot regeneration is
regulated by ESR1, once the explant tissues in the culture medium
acquire the competence for organogenesis.
On
behalf of Bangladesh Association for Plant Tissue Culture (BAPTC)
and its members I offer my heartiest congratulations to Professor
N-H Chua for his personal and his team's outstanding discovery of
ESR1. This finding would surely open us new vista to induce shoot
regeneration to recalcitrant plants. ASIslam
Edible
Plant Vaccines are only 2-4 years from Full Development
In the December
issue of Genetic Engineering News, (vol. 21, # 21:p. 40 & 71), Vicki
Brower writes about what Plant Biotechnology has achieved so far
by way of enhancing crop yields, creating edible plant vaccines
etc. in an article entitled, "Harnessing the Potential of Plant-Based
Biotech." The author describes the research results of Professor
Alexander Karasev and his team at Jefferson Medical College in Philadelphia.
Using spinach,
lettuce and soybeans the team has reported promising results in
developing edible vaccines for HIV and hepatitis B. Besides being
much cheaper, plant vaccines are safe and in a matter of time will
be within the purchasing capacity of average citizen in developing
countries. Using tobacco mosaic virus (TMV), the group expressed
the Trans-Activating Transduction (TAT) gene in the leaves of Nicotania
benthamiana and spinach. However, they found it necessary to
fuse the tat protein to plant virus capsid proteins in order
to obtain symptoms in the treated plants in the form of leaf curling,
yellowing and stunting of growth. Extractable tat protein
from leaves fully retained immunological reactivity against tat-specific
monoclonal antibodies.
The group has embarked another project in which they have incorporated
the cloned gene into the lettuce genome in order to produce the
recombinant hepatitis B vaccine. Volunteers, who ate the vaccine-containing
lettuce, showed immunity against this deadly disease.
Another
vaccine project, the group has been working on, is the development
a rabies vaccine. The volunteers, who were given spinach containing
the vaccine, showed a good antibody response. According to the author,
these plant vaccines are about 2-4 years from full development.
Meristem
Targets Protein Production in Plants
In
the December issue of Genetic Engineering News, (vol. 21,
# 21, p 72 & 74), Dr. Susan Aldridge, describes the program of a
recently established private pharmaceutical company called, "Meristem
Therapeutics" with its headquarters at Clemont-Ferrand, France.
The objective of the company is to apply a novel system to produce
pharmaceuticals on an industrial scale. The method consists of using
Meristem's specialized cassette to allow the plant cell to recognize
the inserted human gene. Following transformation, the bioengineered
plant cells are transferred to the company's phytotron. Under ideal
conditions of temperature, light and humidity, healthy transgenic
plants develop. After the plants grow to maturity, they are tested
for the human gene targeted to these plant cells and then analyzed
for expression level. Individual plants showing an acceptable level
of protein are multiplied and their seeds are planted in fields
in the US and France during summer and in Chile during the winter
months Already, using this method the company has been able to produce
1 mg of extracted recombinant protein per one gram of corn. Although
this is quite an achievement, the company thinks production may
be further enhanced with the improvement of techniques. Because
the technology is field- and not factory-based, the company is confident
that their products will be much cheaper compared to factory-produced
pharmaceuticals.
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