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Lecture- 39

Other terms that nearly mean the same thing are:

• Genetically engineered organisms

• Transgenics

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Genetically modified organisms (GMOs) can be defined as organisms in which the genetic material (DNA) has been altered in a way that does not occur naturally by mating and/or natural recombination. Selected individual genes are transferred from one organism into another, also between nonrelated species. Foods produced from or using GM organisms are often referred to as GM foods.

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•Many genetically modified organisms (GMOs) have been producedwith the help of recombinant DNA technology.

•A GMO is made by making modifications in the genome of anorganism. This may or may not involve the introduction of a foreignDNA molecule.

•If a foreign gene(s) is introduced in an organism, the organism isknown as a transgenic organism. The E.coli transgenics containinghuman somatostatin, insulin and leukocyte (IFNα) interferon geneswere constructed in the years 1977, 1979 and 1980, respectively.

•Subsequently, transgenics of E. coli containing several other foreigngenes were constructed. Genetically-modified microorganisms havebeen successfully used in environmental pollution control andextraction of minerals from crude ores.

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• In the year 1980, a research group led by Jon Wright succeeded in

making transgenic mouse embryos. Five years later production of

transgenic rabbits, sheep and pigs were reported by R. E. Hammer and

coworkers.

• Transgenic goats containing human blood protein antithrombin were

made in 2009.

• The protein produced in the milk of these goats was approved by the

US Food and Drug Administration for use as a drug under the name

ATryn.

• A research group led by Donald Jarvis, working at University of

Wyoming, USA, reported in 2012 the construction of spider gene-

expressing silkworms producing super-tough silk.

• These transgenic silkworms may be used in future for manufacturing

tough silk fibers.

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• The first transgenic plant was constructed in 1984 by

introduction of the insecticidal protein gene of Bacillus

thuringiensis (Bt) in tobacco plant by Marc Van Montagu and Jeff

Schell, working in the Plant Genetic Systems company.

• This company, based in Ghent, Belgium, was founded by these

scientists, who were the first to construct Agrobacterium

tumefaciens-derived Ti plasmid vectors for introduction of foreign

genes into plants.

• The resulting Bt tobacco plants showed resistance to attacks by

lepidopteran larvae. Subsequently, Bt cotton, marketed as Bollgard

cotton, was introduced by Monsanto company in 1996.

• Bt cotton proved to be a big farm level success globally as this

crop did not require the spray of expensive and harmful chemical

pesticides for control of lepidopteran insects.

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• In the year 1994 Calgene company came up with Flavr Savr tomato which became

first commercially grown genetically-engineered food crop.

• The Flavr Savr tomatoes have a higher economic value because of their increased

shelf-life. SemBioSys Genetics Inc., a Canada-based biotech company, has produced in

2008 transgenic safflower plants containing human insulin gene.

• Human insulin obtained from the flowers of these plants may find therapeutic use in

near future. Genetically modified poplar trees have been developed by the Flanders

Institute of Biotechnology, Belgium.

• These trees, for which field trials were started in 2009, contain 17% more cellulose

and 20% less lignin. The wood from these trees is expected to be very useful in bioethanol

and paper industries.

• Several other transgenic plants, containing foreign genes from different sources, have

been produced. These plants have new and improved characteristics like more yield,

enhanced nutritional quality, disease resistance, production of new compounds, etc.

• In some countries transgenic plants have become controversial because of

environmental concerns, potential health risks and ethical issues.

• Transfer of genes between plant species for cropimprovement can be achieved through naturalmethods (plant breeding) and artificial methods(genetic transformation).

• Genetic transformation facilitates introduction of onlyspecific desirable genes without co-transfer of anyundesirable genes from donor species, which normallyoccurs by conventional breeding method.

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• The capacity to introduce and express diverseforeign genes in plants was first described intobacco

• Resistance conferred to plants is generallyagainst viruses, insects, herbicides and postharvest deterioration

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Insect resistance

• Insect resistance genes can be of plant,bacterial or any other origin.

• Genes conferring insect resistance to plantsthat have been obtained from microorganismsare Bt gene from Bacillus thuringiensis and ipt(isopentenyl transferase) from Agrobacteriumtumefaciens.

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Resistance genes fromplants are classified as:

1. Proteinase and amylase inhibitors

2. Lectins (snowdrop lectin)

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• Bacillus thuringiensis is an entomocidalbacterium that produces an insect controlprotein.

• Several genes encoding these toxins havebeen isolated.

• DNA constructs containing promoter and theactive coding sequences of these toxin geneshave been expressed in plants to confer insectresistance.

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1985

Plant Genetic Systems(Ghent, Belgium)

Founded by

Marc Van Montagu and Jeff Schell,

developed

Bt Tobacco 12

GMO for quality

• The first commercial transgenic foodproduct was “Flavr Savr”(Transgenic tomato)with delayed ripening developed by Calgene,USA in 1994.

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• Long shelf life of tomatoes was developed by twoapproaches :

1. Antisense RNA technology against polygalacturonaseencoding genes (used by Calgene).

2. Using gene for 1-aminocyclopropane-1-carboxylic acid(ACC) deaminase which degrades ACC to ethylene.

Genes encoding ACC and ACO (ACC oxidase) have beencloned from many species.

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• In 1995 potato varieties expressing Bt crystalprotein toxic to Colorado potato beetle weremade commercially available

• In the following years, cotton varietiesexpressing Bt crystal protein toxic to a numberof lepidopteran pests were introduced

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1996

Bt cottonfirst introduced

marketed as Bollgard cotton, a trade mark of Monsanto

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• Bt-corn hybrids with improved resistance toEuropean cornborer became available

• Transgenics for herbicide

tolerance was the dominant

trait for transfer into crops

in 1997

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2008

• Scientists in Hebrew University Jerusalem, Israel enhanced the scent of flowers by ten-fold

• caused it to emit a scent during day and night - irrespectiveof the natural rhythm of scent production

• patented by Yissum, the Hebrew University's technologytransfer company

• Israel is the Middle East's flower-producing superpower ;third only to the Netherlands and Kenya in supplying the EUwith flowers

Scent Enhancement in Flowers

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• Raman and colleagues (University of Texas )have manipulated the flavor enzymes found inArabidopsis thaliana by genetic engineering

• Allene oxide synthase (AOS)

• Hydroperoxide lyase (HPL)

Fruits with more flavors2008

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• SemBioSys Genetics Inc., a Canada based biotechnology company

• Safflower produced recombinant insulin phase I/II clinical trials were conducted in USA

Human insulin in plants2008

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Advantages of GM Plants

• Yield improvement of major food crops

• Introduction of useful traits like resistance todiseases, pests and insects to various cropvarieties

• Increased shelf life.

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