Genetically modified tomato
Encyclopedia
A genetically modified tomato, or transgenic tomato is a tomato
that has had its gene
s modified, using genetic engineering
. The first commercially available genetically modified food
was a tomato engineered to have a longer shelf life
(the Flavr Savr). Currently there are no genetically modified tomatoes available commercially, but scientists are developing tomatoes with new traits like increased resistance to pests or environmental stresses. Other projects aim to enrich tomatoes with substances that may offer health benefits or be more nutritous
. As well as aiming to produce novel crops, scientists produce genetically modified tomatoes to understand the function on genes naturally present in tomatoes.
there are now thousands of varieties grown worldwide. Agrobacterium
-mediated genetic engineering
techniques were developed in the late 1980s that could successfully transfer genetic material into the nuclear
genome
of tomatoes. Genetic material can also be inserted
into a tomato cell's chloroplast
and chromoplast
plastome
s using biolistics. Tomatoes were the first food crop with an edible fruit where this was possible.
to study the fruit ripening of climacteric
fruit. To understand the mechanisms involved in the process of ripening, scientists have genetically engineered tomatoes.
In 1994, the Flavr Savr became the first commercially grown genetically engineered food to be granted a license for human consumption. A second copy of the tomato gene polygalacturonase
was inserted
into the tomato genome in the antisense direction. The polygalacturonase enzyme
degrades pectin
, a component of the tomato cell wall
, causing the fruit to soften. When the antisense gene is expressed it interferes
with the production of the polygalacturonase enzyme, delaying the ripening process. The Flavr Savr failed to achieve commercial success and was withdrawn from the market in 1997. Similar technology, but using a truncated version of the polygalacturonase gene, was used to make a tomato paste
.
DNA Plant Technology
(DNAP), Agritope and Monsanto
developed tomatoes that delayed ripening by preventing the production of ethylene
, a hormone
that triggers ripening of fruit. All three tomatoes inhibited ethylene production by reducing the amount of 1-aminocyclopropane-1-carboxylic acid
(ACC), the precursor
to ethylene. DNAP's tomato, called Endless Summer, inserted a truncated version of the ACC synthase
gene into the tomato that interfered with the endogenous
ACC synthase. Monsanto's tomato was engineered with the ACC deaminase gene from the soil bacterium Pseudomonas chlororaphis
that lowered ethylene levels by breaking down ACC. Agritope introduced an S-adenosylmethionine hydrolase (SAMase) encoding gene derived from the E. coli bacteriophage
T3, which reduced the levels of S-adenosylmethionine, a precursor to ACC. Endless Summer was briefly tested in the marketplace, but patent
arguments forced its withdrawal.
Scientists in India have delayed the ripening of tomatoes by silencing two genes encoding N-glycoprotein
modifying enzymes, α-mannosidase and β-D-N-acetylhexosaminidase. The fruits produced were not visibly damaged after being stored at room temperature for 45 days, whereas unmodified tomatoes had gone rotten. In India, where 30% of fruit is wasted before it reaches the market due to a lack of refrigeration and poor road infrastructure, the researchers hope genetic engineering of the tomato may decrease wastage.
are a limiting factor to the growth of tomatoes. While no genetically modified stress tolerant plants are currently commercialised, transgenic approaches have been researched. An early tomato was developed that contained an antifreeze gene
(afa3) from the winter flounder
with the aim of increasing the tomato's tolerance to frost (see Fish tomato
). The antifreeze protein was found to inhibit ice recrystallization in the flounders blood, but had no effect when expressed in transgenic tobacco. The resulting tomato was never commercialized, but raised ethical questions over adding genes from one kingdom
to another.
Other genes from various species have been inserted into the tomato with the hope of increasing their resistance to various environmental factors. A gene from rice (Osmyb4), which codes for a transcription factor
, that was shown to increase cold and drought tolerance in transgenic Arabidopsis thaliana
plants was inserted into the tomato. This resulted in increased drought tolerance, but did not appear to have any effect on cold tolerance. Overexpressing a vacuolar
Na+/H+ antiport (AtNHX1) from A. thaliana lead to salt accumulating in the leaves of the plants, but not in the fruit and allowed them to grow more in salt solutions than wildtype plants. They were the first salt-tolerant, edible plants ever created. Tobacco osmotic genes overexpressed in tomatoes produced plants that held a higher water content than wildtype plants increasing tolerance to drought and salt stress.
has been inserted into a tomato plant. When field tested they showed resistance to the tobacco hornworm (Manduca sexta), tomato fruitworm (Heliothis zea), the tomato pinworm (Keiferia lycopersicella
) and the tomato fruit borer (Helicoverpa armigera
). A 91 day feeding trail in rats showed no adverse effects, but the Bt tomato has never been commercialised. Tomatoes resistant to a root knot nematode
have been created by inserting a cysteine
proteinase inhibitor
gene from taro
. A chemically synthesised
ceropin B gene, usually found in the giant silk moth (Hyalophora cecropia
), has been introduced into tomato plants and in vivo
studies show significant resistance to bacterial wilt
and bacterial spot
. When the cell wall proteins, polygalacturonase and expansin
are prevented from being produced in fruits, they are less susceptible to the fungus Botrytis cinerea
than normal tomatoes.
was increased by adding a bacterial gene encoding phytoene
desaturase
, although the total amount of carotenoid
s remained equal. The researchers admitted at the time that it had no prospect of being grown commercially due to the anti-GM climate. Sue Meyer of the pressure group Genewatch, told The Independent
that she believed, "If you change the basic biochemistry, you could alter the levels of other nutrients very important for health". More recently, scientists have increased the production of anthocyanin
, an antioxidant
in tomatoes in several ways. One group added a transcription factor
for the production of anthocyanin from Arabidopsis thaliana
whereas another used transcription factors from snapdragon (Antirrhinum
). When the snapdragon genes where used, the fruits had similar anthocyanin concentrations to blackberries and blueberries, and when fed to cancer susceptible mice, extended their life span. Another group has tried to increase the levels of isoflavone
, known for its potential cancer preventative properties, by introducing the soybean isoflavone synthase into tomatoes.
synthase from lemon basil (Ocimum basilicum) was expressed in tomato fruits under a fruit-specific promoter, 60% of untrained taste testers preferred the taste and smell of the transgenic tomatoes. The fruits contained around half the amount of lycopene
, reducing the health benefits of eating them.
es, banana
s and other plants) are being investigated as vehicles for delivering edible vaccines
. Clinical trials have been conducted on mice using tomatoes expressing antibodies or proteins that stimulate antibody production targeted to norovirus, hepatitis B, rabies
, HIV
, anthrax
and respiratory syncytial virus. Korean scientists are looking at using the tomato to expressing a vaccine against Alzheimer's disease
. Hilary Koprowski
, who was involved in the development of the polio vaccine
, is leading a group of researchers in developing a tomato expressing a recombinant vaccine to SARS.
in scientific research and they are frequently genetically modified to further our understanding of particular processes. Tomatoes have been used as a model in map-based cloning, where trangsenic plants must be created to prove that a gene has been successfully isolated. The plant peptide hormone, systemin
was first identified in tomato plants and genetic modification has been used to demonstrate its function, by adding antisense genes to silence the native gene, or by adding extra copies of the native gene.
Tomato
The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...
that has had its gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s modified, using genetic engineering
Genetic engineering
Genetic engineering, also called genetic modification, is the direct human manipulation of an organism's genome using modern DNA technology. It involves the introduction of foreign DNA or synthetic genes into the organism of interest...
. The first commercially available genetically modified food
Genetically modified food
Genetically modified foods are foods derived from genetically modified organisms . Genetically modified organisms have had specific changes introduced into their DNA by genetic engineering techniques...
was a tomato engineered to have a longer shelf life
Shelf life
Shelf life is the length of time that food, drink, medicine, chemicals, and many other perishable items are given before they are considered unsuitable for sale, use, or consumption...
(the Flavr Savr). Currently there are no genetically modified tomatoes available commercially, but scientists are developing tomatoes with new traits like increased resistance to pests or environmental stresses. Other projects aim to enrich tomatoes with substances that may offer health benefits or be more nutritous
Human nutrition
Human nutrition is the provision to humans to obtain the materials necessary to support life. In general, humans can survive for two to eight weeks without food, depending on stored body fat and muscle mass. Survival without water is usually limited to three or four days...
. As well as aiming to produce novel crops, scientists produce genetically modified tomatoes to understand the function on genes naturally present in tomatoes.
Background
The tomato originated from South America and was brought to Europe by the Spanish in the 16th century. Wild tomatoes are small, green and largely unappetizing, but after centuries of breedingPlant breeding
Plant breeding is the art and science of changing the genetics of plants in order to produce desired characteristics. Plant breeding can be accomplished through many different techniques ranging from simply selecting plants with desirable characteristics for propagation, to more complex molecular...
there are now thousands of varieties grown worldwide. Agrobacterium
Agrobacterium
Agrobacterium is a genus of Gram-negative bacteria established by H. J. Conn that uses horizontal gene transfer to cause tumors in plants. Agrobacterium tumefaciens is the most commonly studied species in this genus...
-mediated genetic engineering
Genetic engineering
Genetic engineering, also called genetic modification, is the direct human manipulation of an organism's genome using modern DNA technology. It involves the introduction of foreign DNA or synthetic genes into the organism of interest...
techniques were developed in the late 1980s that could successfully transfer genetic material into the nuclear
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
of tomatoes. Genetic material can also be inserted
Transplastomic plant
A transplastomic plant is a genetically modified plant in which the new genes have not been inserted in the nuclear DNA but in the DNA of the chloroplasts...
into a tomato cell's chloroplast
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...
and chromoplast
Chromoplast
Chromoplasts are plastids responsible for pigment synthesis and storage. They, like all other plastids , are organelles found in specific photosynthetic eukaryotic species....
plastome
Plastome
The plastome is the genetic material that is found in plastids in plant cells . It composes part of the entire genome of photosynthetic organisms....
s using biolistics. Tomatoes were the first food crop with an edible fruit where this was possible.
Delayed ripening
Tomatoes have been used as a model organismModel organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
to study the fruit ripening of climacteric
Climacteric (botany)
The climacteric is a stage of fruit ripening associated with ethylene production and cell respiration rise. Apples, bananas, melons, apricots, tomatoes are climacteric fruit. Citrus, grapes, strawberries are non-climacteric...
fruit. To understand the mechanisms involved in the process of ripening, scientists have genetically engineered tomatoes.
In 1994, the Flavr Savr became the first commercially grown genetically engineered food to be granted a license for human consumption. A second copy of the tomato gene polygalacturonase
Polygalacturonase
Polygalacturonase is an enzyme produced in plants which is involved in the ripening process, and by some bacteria and fungi which is involved in the rotting process. PGs degrades polygalacturonan present in the cell walls of plants by hydrolysis of the glycosidic bonds that link galacturonic acid...
was inserted
Transformation (genetics)
In molecular biology transformation is the genetic alteration of a cell resulting from the direct uptake, incorporation and expression of exogenous genetic material from its surroundings and taken up through the cell membrane. Transformation occurs naturally in some species of bacteria, but it can...
into the tomato genome in the antisense direction. The polygalacturonase enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
degrades pectin
Pectin
Pectin is a structural heteropolysaccharide contained in the primary cell walls of terrestrial plants. It was first isolated and described in 1825 by Henri Braconnot...
, a component of the tomato cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...
, causing the fruit to soften. When the antisense gene is expressed it interferes
RNAI
RNAI is a non-coding RNA that is an antisense repressor of the replication of some E. coli plasmids, including ColE1. Plasmid replication is usually initiated by RNAII, which acts as a primer by binding to its template DNA. The complementary RNAI binds RNAII prohibiting it from its initiation role...
with the production of the polygalacturonase enzyme, delaying the ripening process. The Flavr Savr failed to achieve commercial success and was withdrawn from the market in 1997. Similar technology, but using a truncated version of the polygalacturonase gene, was used to make a tomato paste
Tomato paste
Tomato paste is a thick paste that is made by cooking tomatoes for several hours to reduce moisture, straining them to remove the seeds and skin, and cooking them again to reduce them to a thick, rich concentrate...
.
DNA Plant Technology
DNA Plant Technology
DNA Plant Technology was an early pioneer in applying transgenic biotechnology to problems in agriculture. The company was founded in Cinnamonson, New Jersey. In 1994, their headquarters moved to Oakland, California...
(DNAP), Agritope and Monsanto
Monsanto
The Monsanto Company is a US-based multinational agricultural biotechnology corporation. It is the world's leading producer of the herbicide glyphosate, marketed in the "Roundup" brand of herbicides, and in other brands...
developed tomatoes that delayed ripening by preventing the production of ethylene
Ethylene
Ethylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...
, a hormone
Plant hormone
Plant hormones are chemicals that regulate plant growth, which, in the UK, are termed 'plant growth substances'. Plant hormones are signal molecules produced within the plant, and occur in extremely low concentrations. Hormones regulate cellular processes in targeted cells locally and, when moved...
that triggers ripening of fruit. All three tomatoes inhibited ethylene production by reducing the amount of 1-aminocyclopropane-1-carboxylic acid
1-Aminocyclopropane-1-carboxylic acid
1-Aminocyclopropane-1-carboxylic acid is a disubstituted cyclic alpha-amino acid in which a three-membered cyclopropane ring is fuzed to the C-atom of the amino acid....
(ACC), the precursor
Precursor (chemistry)
In chemistry, a precursor is a compound that participates in the chemical reaction that produces another compound. In biochemistry, the term "precursor" is used more specifically to refer to a chemical compound preceding another in a metabolic pathway....
to ethylene. DNAP's tomato, called Endless Summer, inserted a truncated version of the ACC synthase
Synthase
In biochemistry, a synthase is an enzyme that catalyses a synthesis process.Following the EC number classification, they belong to the group of ligases, with lyases catalysing the reverse reaction....
gene into the tomato that interfered with the endogenous
Endogenous
Endogenous substances are those that originate from within an organism, tissue, or cell. Endogenous retroviruses are caused by ancient infections of germ cells in humans, mammals and other vertebrates...
ACC synthase. Monsanto's tomato was engineered with the ACC deaminase gene from the soil bacterium Pseudomonas chlororaphis
Pseudomonas chlororaphis
Pseudomonas chlororaphis is a bacterium used as a soil inoculant in agriculture and horticulture. It can act as a biocontrol agent against certain fungal plant pathogens via production of phenazine type antibiotics. Based on 16S rRNA analysis, P. chlororaphis has been placed in the P. chlororaphis...
that lowered ethylene levels by breaking down ACC. Agritope introduced an S-adenosylmethionine hydrolase (SAMase) encoding gene derived from the E. coli bacteriophage
Bacteriophage
A bacteriophage is any one of a number of viruses that infect bacteria. They do this by injecting genetic material, which they carry enclosed in an outer protein capsid...
T3, which reduced the levels of S-adenosylmethionine, a precursor to ACC. Endless Summer was briefly tested in the marketplace, but patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....
arguments forced its withdrawal.
Scientists in India have delayed the ripening of tomatoes by silencing two genes encoding N-glycoprotein
Glycoprotein
Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...
modifying enzymes, α-mannosidase and β-D-N-acetylhexosaminidase. The fruits produced were not visibly damaged after being stored at room temperature for 45 days, whereas unmodified tomatoes had gone rotten. In India, where 30% of fruit is wasted before it reaches the market due to a lack of refrigeration and poor road infrastructure, the researchers hope genetic engineering of the tomato may decrease wastage.
Environmental stress tolerance
Abiotic stresses like frost, drought and increased salinitySalinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
are a limiting factor to the growth of tomatoes. While no genetically modified stress tolerant plants are currently commercialised, transgenic approaches have been researched. An early tomato was developed that contained an antifreeze gene
Antifreeze protein
Antifreeze proteins or ice structuring proteins refer to a class of polypeptides produced by certain vertebrates, plants, fungi and bacteria that permit their survival in subzero environments. AFPs bind to small ice crystals to inhibit growth and recrystallization of ice that would otherwise be...
(afa3) from the winter flounder
Winter flounder
The winter flounder, Pseudopleuronectes americanus, is a right-eyed flatfish of the family Pleuronectidae. It is native to coastal waters of the western north Atlantic coast, from Labrador, Canada to Georgia, United States...
with the aim of increasing the tomato's tolerance to frost (see Fish tomato
Fish tomato
Informally referred to as the "fish tomato", DNA Plant Technology's transgenic tomato is genetically engineered with a gene from the winter flounder....
). The antifreeze protein was found to inhibit ice recrystallization in the flounders blood, but had no effect when expressed in transgenic tobacco. The resulting tomato was never commercialized, but raised ethical questions over adding genes from one kingdom
Kingdom (biology)
In biology, kingdom is a taxonomic rank, which is either the highest rank or in the more recent three-domain system, the rank below domain. Kingdoms are divided into smaller groups called phyla or divisions in botany...
to another.
Other genes from various species have been inserted into the tomato with the hope of increasing their resistance to various environmental factors. A gene from rice (Osmyb4), which codes for a transcription factor
Transcription factor
In molecular biology and genetics, a transcription factor is a protein that binds to specific DNA sequences, thereby controlling the flow of genetic information from DNA to mRNA...
, that was shown to increase cold and drought tolerance in transgenic Arabidopsis thaliana
Arabidopsis thaliana
Arabidopsis thaliana is a small flowering plant native to Europe, Asia, and northwestern Africa. A spring annual with a relatively short life cycle, arabidopsis is popular as a model organism in plant biology and genetics...
plants was inserted into the tomato. This resulted in increased drought tolerance, but did not appear to have any effect on cold tolerance. Overexpressing a vacuolar
Vacuole
A vacuole is a membrane-bound organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution, though in certain...
Na+/H+ antiport (AtNHX1) from A. thaliana lead to salt accumulating in the leaves of the plants, but not in the fruit and allowed them to grow more in salt solutions than wildtype plants. They were the first salt-tolerant, edible plants ever created. Tobacco osmotic genes overexpressed in tomatoes produced plants that held a higher water content than wildtype plants increasing tolerance to drought and salt stress.
Pest resistance
The insecticidal toxin from the bacterium Bacillus thuringiensisBacillus thuringiensis
Bacillus thuringiensis is a Gram-positive, soil-dwelling bacterium, commonly used as a biological pesticide; alternatively, the Cry toxin may be extracted and used as a pesticide. B...
has been inserted into a tomato plant. When field tested they showed resistance to the tobacco hornworm (Manduca sexta), tomato fruitworm (Heliothis zea), the tomato pinworm (Keiferia lycopersicella
Keiferia lycopersicella
The Tomato Pinworm is a moth of the Gelechiidae family. It is found in warm areas in Mexico, California, Texas, Georgia, Florida, Hawaii, Cuba, Haiti and the Bahamas. It has also been reported from greenhouses in Delaware, Mississippi, Missouri, Pennsylvania and Virginia.The wingspan is 9-12 mm...
) and the tomato fruit borer (Helicoverpa armigera
Helicoverpa armigera
The cotton bollworm, corn earworm or Old World bollworm, Helicoverpa armigera, is a moth, the larvae of which feed on a wide range of plants, including many important cultivated crops. It is a major pest in cotton and one of the most polyphagous and cosmopolitan pest species...
). A 91 day feeding trail in rats showed no adverse effects, but the Bt tomato has never been commercialised. Tomatoes resistant to a root knot nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
have been created by inserting a cysteine
Cysteine
Cysteine is an α-amino acid with the chemical formula HO2CCHCH2SH. It is a non-essential amino acid, which means that it is biosynthesized in humans. Its codons are UGU and UGC. The side chain on cysteine is thiol, which is polar and thus cysteine is usually classified as a hydrophilic amino acid...
proteinase inhibitor
Protease inhibitor (biology)
In biology and biochemistry, protease inhibitors are molecules that inhibit the function of proteases. Many naturally occurring protease inhibitors are proteins....
gene from taro
Taro
Taro is a common name for the corms and tubers of several plants in the family Araceae . Of these, Colocasia esculenta is the most widely cultivated, and is the subject of this article. More specifically, this article describes the 'dasheen' form of taro; another variety is called eddoe.Taro is...
. A chemically synthesised
Gene synthesis
Artificial gene synthesis is the process of synthesizing a gene in vitro without the need for initial template DNA samples. The main method is currently by oligonucleotide synthesis from digital genetic sequences and subsequent annealing of the resultant fragments...
ceropin B gene, usually found in the giant silk moth (Hyalophora cecropia
Hyalophora cecropia
The Cecropia Moth is North America's largest native moth. It is a member of the Saturniidae family, or giant silk moths. Females with a wingspan of 160 mm or more have been documented. It is found as far west as the Rocky Mountains and north into the maritime provinces of Canada...
), has been introduced into tomato plants and in vivo
In vivo
In vivo is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research...
studies show significant resistance to bacterial wilt
Bacterial wilt
Bacterial wilt is a cucurbit disease caused by the pathogen Erwinia tracheiphila, a Gram-negative bacterium in the family Enterobacteriaceae. Cucumber and muskmelon plants are most susceptible, but squash, pumpkins, and gourds may also become infected. Watermelons are immune to the disease.-...
and bacterial spot
Xanthomonas campestris
Xanthomonas campestris is a bacterial species that causes a variety of plant diseases. Available from the NCPPB,and other international Culture collections such as ICMP, ATCC, and LMG in a purified form, it is used in the commercial production of a high-molecular-weight polysaccharide - xanthan...
. When the cell wall proteins, polygalacturonase and expansin
Expansin
Expansin refers to a family of closely related nonenzymatic proteins found in the plant cell wall, with important roles in plant cell growth, fruit softening, abscission, emergence of root hairs, pollen tube invasion of the stigma and style, meristem function, and other developmental processes...
are prevented from being produced in fruits, they are less susceptible to the fungus Botrytis cinerea
Botrytis cinerea
Botrytis cinerea is a necrotrophic fungus that affects many plant species, although its most notable hosts may be wine grapes. In viticulture, it is commonly known as botrytis bunch rot; in horticulture, it is usually called grey mould or gray mold.The fungus gives rise to two different kinds of...
than normal tomatoes.
Improved nutrition
Tomatoes have been altered in attempts to improve their flavour or nutritional content. In 2000, the concentration of pro-vitamin AVitamin A
Vitamin A is a vitamin that is needed by the retina of the eye in the form of a specific metabolite, the light-absorbing molecule retinal, that is necessary for both low-light and color vision...
was increased by adding a bacterial gene encoding phytoene
Phytoene
Phytoene is a 40-carbon intermediate in the biosynthesis of carotenoids. The synthesis of phytoene is the committed step in the synthesis of carotenoids in plants. Phytoene is produced from two molecules of geranylgeranyl pyrophosphate by the action of the enzyme phytoene synthase...
desaturase
Desaturase
A fatty acid desaturase is an enzyme that removes two hydrogen atoms from a fatty acid, creating a carbon/carbon double bond. These desaturases are classified as...
, although the total amount of carotenoid
Carotenoid
Carotenoids are tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria, and some types of fungus. Carotenoids can be synthesized fats and other basic organic metabolic building...
s remained equal. The researchers admitted at the time that it had no prospect of being grown commercially due to the anti-GM climate. Sue Meyer of the pressure group Genewatch, told The Independent
The Independent
The Independent is a British national morning newspaper published in London by Independent Print Limited, owned by Alexander Lebedev since 2010. It is nicknamed the Indy, while the Sunday edition, The Independent on Sunday, is the Sindy. Launched in 1986, it is one of the youngest UK national daily...
that she believed, "If you change the basic biochemistry, you could alter the levels of other nutrients very important for health". More recently, scientists have increased the production of anthocyanin
Anthocyanin
Anthocyanins are water-soluble vacuolar pigments that may appear red, purple, or blue according to pH...
, an antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...
in tomatoes in several ways. One group added a transcription factor
Transcription factor
In molecular biology and genetics, a transcription factor is a protein that binds to specific DNA sequences, thereby controlling the flow of genetic information from DNA to mRNA...
for the production of anthocyanin from Arabidopsis thaliana
Arabidopsis thaliana
Arabidopsis thaliana is a small flowering plant native to Europe, Asia, and northwestern Africa. A spring annual with a relatively short life cycle, arabidopsis is popular as a model organism in plant biology and genetics...
whereas another used transcription factors from snapdragon (Antirrhinum
Antirrhinum
Antirrhinum is a genus of plants commonly known as snapdragons from the flowers' fancied resemblance to the face of a dragon that opens and closes its mouth when laterally squeezed...
). When the snapdragon genes where used, the fruits had similar anthocyanin concentrations to blackberries and blueberries, and when fed to cancer susceptible mice, extended their life span. Another group has tried to increase the levels of isoflavone
Isoflavone
Isoflavones comprise a class of organic compounds, often naturally occurring, related to the isoflavonoids. Many act as phytoestrogens in mammals...
, known for its potential cancer preventative properties, by introducing the soybean isoflavone synthase into tomatoes.
Improved taste
When geraniolGeraniol
Geraniol is a monoterpenoid and an alcohol. It is the primary part of rose oil, palmarosa oil, and citronella oil . It also occurs in small quantities in geranium, lemon, and many other essential oils. It appears as a clear to pale-yellow oil that is insoluble in water, but soluble in most common...
synthase from lemon basil (Ocimum basilicum) was expressed in tomato fruits under a fruit-specific promoter, 60% of untrained taste testers preferred the taste and smell of the transgenic tomatoes. The fruits contained around half the amount of lycopene
Lycopene
Lycopene is a bright red carotene and carotenoid pigment and phytochemical found in tomatoes and other red fruits and vegetables, such as red carrots, watermelons and papayas...
, reducing the health benefits of eating them.
Vaccines
Tomatoes (along with potatoPotato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...
es, banana
Banana
Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red....
s and other plants) are being investigated as vehicles for delivering edible vaccines
Plant expressed vaccine
Plant expressed vaccine or project GreenVax In 2000, a patented entitled Vaccines expressed in plants was issued. In 2005 DARPA’s Accelerated Manufacture of Pharmaceuticals program was created In response to emerging and novel biologic threats...
. Clinical trials have been conducted on mice using tomatoes expressing antibodies or proteins that stimulate antibody production targeted to norovirus, hepatitis B, rabies
Rabies
Rabies is a viral disease that causes acute encephalitis in warm-blooded animals. It is zoonotic , most commonly by a bite from an infected animal. For a human, rabies is almost invariably fatal if post-exposure prophylaxis is not administered prior to the onset of severe symptoms...
, HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
, anthrax
Anthrax
Anthrax is an acute disease caused by the bacterium Bacillus anthracis. Most forms of the disease are lethal, and it affects both humans and other animals...
and respiratory syncytial virus. Korean scientists are looking at using the tomato to expressing a vaccine against Alzheimer's disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...
. Hilary Koprowski
Hilary Koprowski
Hilary Koprowski is a Polish virologist and immunologist, and inventor of the world's first effective live polio vaccine.-Life:...
, who was involved in the development of the polio vaccine
Polio vaccine
Two polio vaccines are used throughout the world to combat poliomyelitis . The first was developed by Jonas Salk and first tested in 1952. Announced to the world by Salk on April 12, 1955, it consists of an injected dose of inactivated poliovirus. An oral vaccine was developed by Albert Sabin...
, is leading a group of researchers in developing a tomato expressing a recombinant vaccine to SARS.
Basic research
Tomatoes are used as a model organismModel organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
in scientific research and they are frequently genetically modified to further our understanding of particular processes. Tomatoes have been used as a model in map-based cloning, where trangsenic plants must be created to prove that a gene has been successfully isolated. The plant peptide hormone, systemin
Systemin
Systemin is a plant peptide hormone involved in the wound response in the Solanaceae plant family, it was the first plant hormone that was proven to be a peptide. It was discovered in tomato leaves in 1991, since then other peptides, with similar functions have been identified in tomato and outside...
was first identified in tomato plants and genetic modification has been used to demonstrate its function, by adding antisense genes to silence the native gene, or by adding extra copies of the native gene.