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 is most often taken advantage by genetic engineers through selecting cells that can successfully be transformed into an adult plant which can then be grown into multiple new plants containing 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
Nicotiana. Major advances in tissue culture and
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. 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
Sequencing, has abundant
Bioinformatics 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 Mutagenesis, genetic engineering allows targeted removal without disrupting other genes in the organism.
Ornamental
Some genetically modified plants are purely
Ornamental plant. They are modified for flower color, fragrance, flower shape and plant architecture.
The first genetically modified ornamentals commercialised altered colour.
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 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
Platanus.
The papaya ringspot virus (PRSV) devastated papaya trees in Hawaii in the twentieth century until transgenic
papaya 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).
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, 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. GM crops contribute by improving harvests through reducing insect pressure, increasing nutrient value and tolerating different . Despite this potential, as of 2018, the commercialised crops are limited mostly to like cotton, soybean, maize and canola and the vast majority of the introduced traits provide either herbicide tolerance or insect resistance.[ISAAA 2013 Annual Report 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 and parts of Asia and little in Europe and Africa.
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 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.
is the most well known GM crop that is aimed at increasing nutrient value. It has been engineered with three genes that
beta-carotene, a precursor of
Retinol, 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
, 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
Lemna Lemna minor,
the
algae Chlamydomonas reinhardtii[(10 December 2012) " Engineering algae to make complex anti-cancer 'designer' drug" PhysOrg, Retrieved 15 April 2013] and the
moss Physcomitrella patens.
Biopharmaceuticals produced include
,
,
Antibody,
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
and
.
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,
[ Protalix technology platform ] including a drug treatment for Gaucher's disease.
[Gali Weinreb and Koby Yeshayahou for Globes 2 May 2012. " FDA approves Protalix Gaucher treatment "]
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.
