Genetically modified plants have been engineered for scientific research, to create new colours in plants, deliver vaccines, and to create enhanced crops. Plant genomes can be engineered by physical methods or by use of ''
Agrobacterium'' for the delivery of sequences hosted in
T-DNA binary vectors. Many plant cells are
pluripotent, meaning that a single cell from a mature plant can be harvested and then under the right conditions form a new plant. This ability can be taken advantage of by genetic engineers; by selecting for cells that have been successfully transformed in an adult plant a new plant can then be grown that contains the transgene in every cell through a process known as
tissue culture.
Research
Much of the advances in the field genetic engineering has come from experimentation with
tobacco. Major advances in tissue culture and
plant cellular mechanisms for a wide range of plants has originated from systems developed in tobacco. It was the first plant to be genetically engineered and is considered a model organism for not only genetic engineering, but a range of other fields. As such the transgenic tools and procedures are well established making it one of the easiest plants to transform. Another major model organism relevant to genetic engineering is ''
Arabidopsis thaliana
''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small flowering plant native to Eurasia and Africa. ''A. thaliana'' is considered a weed; it is found along the shoulders of roads and in disturbed land.
A winter a ...
.'' Its small genome and short life cycle makes it easy to manipulate and it contains many
homologs to important crop species. It was the first plant
sequenced, has abundant
bioinformatic resources and can be transformed by simply dipping a flower in a transformed ''Agrobacterium'' solution.
In research, plants are engineered to help discover the functions of certain genes. The simplest way to do this is to remove the gene and see what
phenotype develops compared to the
wild type form. Any differences are possibly the result of the missing gene. Unlike
mutagenisis, genetic engineering allows targeted removal without disrupting other genes in the organism.
Some genes are only expressed in certain tissue, so reporter genes, like
GUS, can be attached to the gene of interest allowing visualisation of the location. Other ways to test a gene is to alter it slightly and then return it to the plant and see if it still has the same effect on phenotype. Other strategies include attaching the gene to a strong
promoter and see what happens when it is over expressed, forcing a gene to be expressed in a different location or at different
developmental stages.
Ornamental
Some genetically modified plants are purely
ornamental Ornamental may refer to:
*Ornamental grass, a type of grass grown as a decoration
*Ornamental iron, mild steel that has been formed into decorative shapes, similar to wrought iron work
*Ornamental plant, a plant that is grown for its ornamental qua ...
. They are modified for flower color, fragrance, flower shape and plant architecture.
The first genetically modified ornamentals commercialised altered colour.
Carnations were released in 1997, with the most popular genetically modified organism, a
blue rose (actually lavender or mauve) created in 2004. The roses are sold in Japan, the United States, and Canada. Other genetically modified ornamentals include
Chrysanthemum
Chrysanthemums (), sometimes called mums or chrysanths, are flowering plants of the genus ''Chrysanthemum'' in the family Asteraceae. They are native to East Asia and northeastern Europe. Most species originate from East Asia and the center ...
and
Petunia.
As well as increasing aesthetic value there are plans to develop ornamentals that use less water or are resistant to the cold, which would allow them to be grown outside their natural environments.
Conservation
It has been proposed to genetically modify some plant species threatened by extinction to be resistant invasive plants and diseases, such as the
emerald ash borer in North American and the fungal disease,
Ceratocystis platani, in European
plane trees.
The
papaya ringspot virus (PRSV) devastated papaya trees in Hawaii in the twentieth century until transgenic
papaya
The papaya (, ), papaw, () or pawpaw () is the plant species ''Carica papaya'', one of the 21 accepted species in the genus ''Carica'' of the family Caricaceae. It was first domesticated in Mesoamerica, within modern-day southern Mexico and ...
plants were given pathogen-derived resistance. However, genetic modification for conservation in plants remains mainly speculative. A unique concern is that a transgenic species may no longer bear enough resemblance to the original species to truly claim that the original species is being conserved. Instead, the transgenic species may be genetically different enough to be considered a new species, thus diminishing the conservation worth of genetic modification.
Crops
Genetically modified crops are genetically modified plants that are used in
agriculture. The first crops provided are used for animal or human food and provide resistance to certain pests, diseases, environmental conditions, spoilage or chemical treatments (e.g. resistance to a
herbicide
Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...
). The second generation of crops aimed to improve the quality, often by altering the
nutrient profile. Third generation genetically modified crops can be used for non-food purposes, including the production of
pharmaceutical agents,
biofuels
Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (E ...
, and other industrially useful goods, as well as for
bioremediation.
There are three main aims to agricultural advancement; increased production, improved conditions for agricultural workers and
sustainability
Specific definitions of sustainability are difficult to agree on and have varied in the literature and over time. The concept of sustainability can be used to guide decisions at the global, national, and individual levels (e.g. sustainable livi ...
. GM crops contribute by improving harvests through reducing insect pressure, increasing nutrient value and tolerating different
abiotic stresses. Despite this potential, as of 2018, the commercialised crops are limited mostly to
cash crops like cotton, soybean, maize and canola and the vast majority of the introduced traits provide either herbicide tolerance or insect resistance.
Soybeans accounted for half of all genetically modified crops planted in 2014.
Adoption by farmers has been rapid, between 1996 and 2013, the total surface area of land cultivated with GM crops increased by a factor of 100, from to 1,750,000 km
2 (432 million acres).
[ISAAA 2013 Annual Repor]
Executive Summary, Global Status of Commercialized Biotech/GM Crops: 2013
ISAAA Brief 46-2013, Retrieved 6 August 2014 Geographically though the spread has been very uneven, with strong growth in the
Americas
The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World.
Along with th ...
and parts of Asia and little in Europe and Africa.
Its
socioeconomic spread has been more even, with approximately 54% of worldwide GM crops grown in
developing countries in 2013.
Food
The majority of GM crops have been modified to be resistant to selected herbicides, usually a
glyphosate or
glufosinate based one. Genetically modified crops engineered to resist herbicides are now more available than conventionally bred resistant varieties;
in the USA 93% of soybeans and most of the
GM maize grown is glyphosate tolerant. Most currently available genes used to engineer insect resistance come from the ''
Bacillus thuringiensis
''Bacillus thuringiensis'' (or Bt) is a gram-positive, soil-dwelling bacterium, the most commonly used biological pesticide worldwide. ''B. thuringiensis'' also occurs naturally in the gut of caterpillars of various types of moths and butterflie ...
'' bacterium. Most are in the form of
delta endotoxin genes known as cry proteins, while a few use the genes that encode for
vegetative insecticidal proteins. The only gene commercially used to provide insect protection that does not originate from ''B. thuringiensis'' is the
Cowpea trypsin inhibitor (CpTI). CpTI was first approved for use cotton in 1999 and is currently undergoing trials in rice.
Less than one percent of GM crops contained other traits, which include providing virus resistance, delaying senescence, modifying flower colour and altering the plants composition.
Golden rice is the most well known GM crop that is aimed at increasing nutrient value. It has been engineered with three genes that
biosynthesise beta-carotene, a precursor of
vitamin A, in the edible parts of rice.
It is intended to produce a fortified food to be grown and consumed in areas with a
shortage of dietary vitamin A. a deficiency which each year is estimated to kill 670,000 children under the age of 5 and cause an additional 500,000 cases of irreversible childhood blindness.
The original golden rice produced 1.6μg/g of the
carotenoids, with further development increasing this 23 times.
In 2018 it gained its first approvals for use as food.
Biopharmaceuticals
Plants and plant cells have been genetically engineered for production of
biopharmaceuticals in
bioreactors, a process known as
Pharming. Work has been done with
duckweed ''
Lemna minor'', the
algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
''
Chlamydomonas reinhardtii'' and the
moss
Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...
''
Physcomitrella patens''. Biopharmaceuticals produced include
cytokines
Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrin ...
,
hormones
A hormone (from the Ancient Greek, Greek participle , "setting in motion") is a class of cell signaling, signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and beh ...
,
antibodies
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
,
enzymes
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...
and vaccines, most of which are accumulated in the plant seeds. Many drugs also contain natural plant ingredients and the pathways that lead to their production have been genetically altered or transferred to other plant species to produce greater volume and better products.
Other options for bioreactors are
biopolymers and
biofuels
Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (E ...
. Unlike bacteria, plants can modify the proteins post-
translationally, allowing them to make more complex molecules. They also pose less risk of being contaminated. Therapeutics have been cultured in transgenic carrot and tobacco cells, including a drug treatment for
Gaucher's disease.
Vaccines
Vaccine production and storage has great potential in transgenic plants. Vaccines are expensive to produce, transport and administer, so having a system that could produce them locally would allow greater access to poorer and developing areas.
As well as purifying vaccines expressed in plants, it is also possible to produce edible vaccines in plants. Edible vaccines stimulate the
immune system when ingested to protect against certain diseases. Being stored in plants reduces the long-term cost as they can be disseminated without the need for cold storage, do not need to be purified, and have long term stability. Also being housed within plant cells provides some protection from the gut acids upon digestion; the cost of developing, regulating and containing transgenic plants is high, leading to most current plant-based vaccine development being applied to
veterinary medicine, where the controls are not as strict.
References
{{DEFAULTSORT:Genetically Modified Plant
Genetic engineering
Genetically modified organisms in agriculture