Elaine Law, UBC, 2002

Plant BreedingFor years, framers have been selecting for certainfeatures in crops producing plants that are easier togrow, tastier, and bigger without knowing the exactmechanism of how this occurs.

Recognizing valuable traits and incorporatingthem into future generations is veryimportant in plant breeding

Advances in plant biotechnology hasmade it possible to identify andmodify genes controlling specificcharacteristics.

Nowadays scientists can transfer genes from oneorganism to another unrelated organism, producingwhat is now known as “genetically modifiedorganism” or “transgenic animal/plant”.

Any food produced this way is called GM food

A Little Bit of History……Transgenic plants were first created in the early1980s by three groups working independently.

‘83 ‘84 ‘85 ‘86 ‘87 ‘88 ‘89 ‘90 ‘91 ‘92 ‘93 ‘94 ‘95 ‘96 ‘97 ‘98 ‘99 ‘00 ‘01 ‘02

Firsttransgenic

plant

Delay-ripening tomatoCommercialized in the US

Firstfieldtests6/92

Herbicideresistant, insectresistant plantscommercialized

GM maizeapproved by EU

FirstBt cornplants6/90

Rotting resistant tomatoapproved by FDA

These early transgenic plants were resistant toantibiotics and cancer drug, demonstrating thepotential of transgenic plants. Subsequent researchhas developed transgenic plants with commerciallyuseful traits such as resistance to herbicides, insects,and viruses.

Why Produce GM Food?

Traditionally, combining the desirable genes in oneplant is a long and laborious process, involvingcrossing one plant to another plant of the samespecies or related species.

From economical and agriculturalstandpoints, it is advantageousto grow crops that have higheryield or improved quality, pest ordisease resistance, or toleranceto heat, cold and drought.

Desirable genes may provide means forplants to combat these conditions.

The development oftransgenic technologyallows useful genes fromvarious living sources tobe brought together in arelatively simple manner.

Increase tolerance to adverse growingconditions, e.g. cold/heat/drought

Advantages of GM Food:

Selectively reduce allergy-causing propertiesof some foods

Increase crop yields, e.g. increase the sizeand number of seed

Improve sensory attributes of food, e.g.flavor, texture

Provide resistance to pests and reduce theuse of pesticides

Increase the nutritional value of crops, e.g.increase the protein content of rice

The United Nations estimated that with the worldpopulation reaching 7.15 billion by 2015, 575 millionpeople will face chronic malnutrition and famine.

By increasing crop production and nutrientcomposition, GM food has the potential to reducehunger, malnutrition, and perhaps alleviates poverty

Identifying a Desirable Gene

Modifying the Gene

Making a Transgenic Plant

This iscurrentlythe rate

limiting stepof making atransgenic

plant.

To ensure that the gene is expressed(translated into protein product) at theright place and time, a promoter sequenceis added.

We know very little about the specific genesthat determine plant characteristics.

Effort focused at sequencing andunderstanding the functions of genes inagriculturally important plant species wouldaccelerate this process immensely.

Size?

Color?Heat tolerance ?

Taste?

Genedonor Extract

DNA Isolatethe gene

Certainmodifications

take placeprior to a

gene’sintroduction

to a planthost.

Changing the sequence of the gene canalso optimize resultant protein function.

Successful incorporation of the transgeneis a rare event in plants; therefore amarker gene (e.g. drug resistance) isusually added to allow selection

Gene Gun

Clone intovector

Marker gene construct

tr a n

sfo r m a t i o

n

Put intobacteria

Manybacteria

Manyconstructs

=

Transformation

There are twomethods of

transformation:Gene Gun and

Agrobacteriuminfection

Gene Guna.k.a. microprojectilebombardment or biolistics

Double click this icon to see a movie preparedby the University of Nebraska describing howgene gun works.

Gold particle coated with the DNAcontaining the gene of interest is shotinto the nucleus of a plant cell, the DNAwill detach and may become incorporatedinto the plant chromosomes.

Agrobacterium Infection

Transformation Con’t

Agrobacterium tumefaciens is a species of bacteriacommonly found in soil. This bacteria has the amazingability to infect plant cells with a piece of its own DNAcalled T-DNA.

Upon infection, the T-DNA will integrate into the plantchromosome, takeovers the plant's cellular machinery anduses it to produce more bacteria.

Ti-PlasmidT-DNA

A plant that is wounded will besusceptible to Agrobacteriuminfection and develop tumors.

To use Agrobacterium as amean to incorporatetransgenes in plantchromosomes, scientists haveremoved the tumor-causinggenes on the T-DNA, but leftthe bacteria’s abilities toinfect a plant and transfer itsT-DNA intact.

Tumor caused byAgrobacteria

Selection oftransformed cells

Culture the plant cell withAgrobacteria carrying the

transgene

The recombinant DNA will betransferred to the plant cell

Geneticallymodified plant

Regeneration ofthe plant

Agrobacterium

SaskatchewanAgricultural

BiotechnologyInformation Centre

Click the icon below tosee the movie “how to

make a transgenic plant”made by the

After the plant cells are infected withAgrobacteria, they are transferred to aselective media where cells that did notincorporate the transgene will die.

The cells which harbor the transgeneare then regenerated in media containingnutrients and growth hormones.

Selection and Regeneration

If a plant passes thesetests, it is rarely directlyused for crop production,instead it will be crossedwith an improved line ofthe crop.

Testing the transgenic plant

Once a transgenic plant is obtained,a set of extensive tests has to bedone. Every transgenic plant must beverified for the incorporation of thetransgene.

If the transgene is present, the plant isevaluated for any adverse effects imposedby the transgene.

Assays are done to determinethe activity of the transgene,whether this gene is passedstably from one generation tothe next, and whether there areunforeseen effects on plantgrowth, yield, and quality.

Roundup Ready™ Soybeans

Some Examples of CurrentTransgenic Plants

A problem in agriculture is the reduced growth of cropsimposed by the presence of unwanted weeds. Herbicidessuch as RoundupTM and Liberty LinkTM are able to kill awide range of weeds and have the advantage of breakingdown easily. Development of herbicide resistant cropsallows the elimination of surrounding weeds without harmto the crops.

Increase Yields

Crops can be modifiedto optimize growthconditions: improve

nitrogen assimilation,increase oxygen

absorption, efficientphotosynthetic

pathway, and increasestarch biosynthesis. Transgenic plant

modified to haveincrease yield

Unmodifiedcontrol plant

Insect Resistance

Corn hybrid with aBt gene

Corn hybridsusceptible toEuropean corn

borer

Various insectresistant crops havebeen produced. Mostof these make use of

the Cry gene in thebacteria Bacillus

thuringiensis (Bt);this gene directs the

production of aprotein that causes

paralysis and death tomany insects.

Normal rice

“Golden” rice

Golden Rice

Transgenic technologyproduced a type of rice that

accumulates beta-carotenein rice grains. Once inside

the body, beta-carotene isconverted to vitamin A.

More than 120 millionchildren in the world

suffers from vitamin Adeficiency. Golden Rice has

the potential to helpprevent the 1 to 2 million

deaths each year caused bya deficiency in this vitamin.

Papaya infectedwith the papaya

ringspot virus

Virus resistancegene introduced

Virus Resistant Crops

The Freedom IIsquash has a modifiedcoat protein thatconfer resistance tozucchini yellows mosaicvirus and watermelonmosaic virus II.Scientists are nowtrying to develop cropswith as many as fivevirus resistance genes

Pharmaceutical Production in PlantsGenetically modified plants have been used as“bioreactors” to produce therapeutic proteinsfor more than a decade. A recent contributionby transgenic plants is the generation of ediblevaccines.

Edible vaccines are vaccines produced in plantsthat can be administered directly through theingestion of plant materials containing the vaccine.Eating the plant would then confer immunityagainst diseases.Edible vaccines produced bytransgenic plants are attractive formany reasons. The cost associatedwith the production of the vaccine islow, especially since the vaccine canbe ingested directly, and vaccineproduction can be rapidly up scaledshould the need arises. Ediblevaccine is likely to reach moreindividuals in developing countries.The first human clinical trial tookplace in 1997. Vaccine against thetoxin from the bacteria E.coli wasproduced in potato. Ingestion of thistransgenic potato resulted insatisfactory vaccinations and noadverse effects.

Vol. 19, No. 3Feb. 1, 1999

One focus of current vaccine effort is on hepatitis B, avirus responsible for causing chromic liver disease.Transgenic tobacco and potatoes were engineered toexpress hepatitis B virus vaccine. During the past two years,vaccines against a E.coli toxin, the respiratory syncytialvirus, measles virus, and the Norwalk virus have beensuccessfully expressed in plants and delivered orally. Thesestudies have supported the potential of edible vaccines aspreventive agents of many diseases.

Edible Vaccines

There is hope to produce edible vaccines in bananas, whichare grown extensively throughout the developing world.

Concerns of GM Food

Evolution of super pests that are resistantto all types of herbicides or insecticides

Whether it is ethical to eat a foodcontaining a gene from something one wouldnot eat for religious, health or other reasons

Unintended modification of other species inthe neighboring fields due to cross pollination

Ethics of move genes between plants oranimals which do not normally interbreed

Disturbing the balance of ecosystems bycreating species that normally do not exist

The use of modern biotechnologyin food has evolve rapidly duringthe last decade, without a fullunderstanding of this technologyand its consequences.

As a safety measure, before any GM foods arereleased into the market, they are subjected torigorous safety assessments by the industry andregulatory agencies of the places of origin.

Nutrition FactsServing Size 2 Cookies (33g)Servings per container: 6

Amount per servingCalories 140 Calories from fat 60

Total Fat 6g, 11% Daily ValueSaturated Fat 2.5g 12%Cholesterol 20 mg 7%Sodium 65 mg 3%Total carbohydrate 19g 6%Protein 1gVitamin A 4%

PRODUCED WITH GENETICALLY ENGINEERED INGREDIENTS

INGREDIENTS: UNBLEACHED WHEAT FLOUR, CANOLA OIL, EVAPORATED CANE JUICE, BUTTER, STRAWBERRY JAM (APPLE CONCENTRATE, STRAWBERRY CONCENTRATE, WATER, STRAWBERRIES, LOCUST BEAN GUM, PECTIN, CITRIC ACID), EGGS, WHEY, SALT, BAKING SODA

In the United States, where GM crops are most abundant,they are regulated by three federal agencies: theEnvironmental Protection Agency, the Food and DrugAdministration, and the United States Department ofAgriculture. The assessments, including that performed bythe manufacturers, may take several years to complete, andthe GM food is only released into the market when it meets allthe requirements set out by these agencies.In Canada and the United States, labelingof GM foods is only required when thefood is significantly different from itsconventional counterpart in composition,nutrition and allergenicity.

Concerns of GM Food

References/ResourcesArticles

Ye, X., S. Al-Babili, A. Kli, J. Zhang, P. Lucca, P. Beyer, and I. Potrykus.2000. Engineering the provitamin A (-carotene) biosynthetic pathwayinto (carotenoid-free) rice endosperm. Science 287:303-305.

Chargelegue D, Obregon P, Drake PM. Transgenic plants for vaccineproduction: expectations and limitations. Trends Plant Sci. 2001Nov;6(11):495-6.

Daniell H, Streatfield SJ, Wycoff K.Medical molecular farming:production of antibodies, biopharmaceuticals and edible vaccines inplants. Trends Plant Sci. 2001 May;6(5):219-26.

Richter LJ, Thanavala Y, Arntzen CJ, Mason HS. Production ofhepatitis B surface antigen in transgenic plants for oral immunization.Nat Biotechnol. 2000 Nov;18(11):1167-71.

Moellenbeck, D.J., M.L. Peters, J.W. Bing, L.S. Higgins, L. Sims, et al.2001. Insecticidal proteins from Bacillus thuringiensis protect cornfrom corn rootworms. Nature Biotechnology 19:668-672.

Guerinot, M.L. 2000. Enhanced: the green revolution strikes gold. 2000.Science 287:241-243.

Resources on the Web

Transgenic Crops: and introductory and resource guide-verycomprehesive web site on transgenic plantshttp://www.colostate.edu/programs/lifesciences/TransgenicCrops/index.html

UC Davis Biotechnology Program-has a series of PowerPointpresentations on transgenic plant http://www.biotech.ucdavis.edu/

Colorado Agricultural Information http://www.csuag.com/

Environmental News Network GM Food Information-containsintroduction to GM food and a quiz on the topichttp://enn.com/indepth/gmfood/index.asp

DNA for Dinnerhttp://www.gis.net/~peacewp/webquest.htm#Introduction

Food for Our Future http://www.foodfuture.org.uk/

Saskatchewan Agricultural Biotechnology Information CentreAgrobacterium animation:http://www.agwest.sk.ca/sabic_index_tp.shtml

University of Nebraska geneg gun animation:http://croptechnology.unl.edu/