Genetic Engineering of plants

for Fatty-acid composition

Genetic engineering......?

Is a type of genetic modification.

purposeful addition of a foreign gene or genes to the

genome of an organism.

not bound by the limitations of traditional plant

breeding.

physically removing the DNA from one organism

and transffering the gene(s) for one or a few traits

into another.

Overcomes the 'sexual' barrier between species.

traits from any living organism can be transferred into

a plant.

more specific in that a single trait can be added to a

plant.

Genetic engineering in action Genetic engineering comes to action where

Plant breeding has its limitations.

Overcomes sexual incompatibility, resulting

in addition of new traits to a species.

When plants are crossed, many undesirable

traits are transferred along with the trait of

interest.

STEPS INVOLVED IN GENETICENGENEERING OF PLANTS….

Step 1: DNA Extraction

A sample of an organism containing thegene of interest is taken through a seriesof steps to remove the DNA.

Step 2 : Gene Cloning

Extraction of the gene of interestfrom the rest of the genome andmaking multiple copies of it.

Step 3 : Gene Design

Done in a test tube by splicing the gene apartwith enzymes and replacing the regions thathave been extracted.

Step 4 : Transformation

Inserting new gene into some of the cellsusing different techniques

Some of the common methods include thegene gun, agrobacterium, microfibers, andelectroporation.

The main goal is to transport the newgene(s) and deliver them into the nucleus ofa cell without killing it.

1.Transformed plant cells are then regenerated into transgenic plants.

2.The transgenic plants are grown to maturity in greenhouses

Step 5 : Backcross Breeding

1. Transgenic plants are crossed with elite breeding lines to combine the

desired traits of elite parents and the transgene into a single line.

2.Offsprings are repeatedly crossed back to the elite line to obtain a high

yielding transgenic line.

3.Results in a plant with a yield potential close to current hybrids that

expresses the trait encoded by the new transgene.

MODIFICATION ACHIEVED ENZYME ENGINEERED SOURCE OF GENE AND

REFERENCE

Lauric acid production Acyl-ACP thioesterase California bay ,Voelker et al, 1992

lncreased stearic acid Antisense of stearoyl-ACP

Stearyl-COA desaturase

Brassica napus, ,Knutzon et al., 1992

Rat, Crayburn et al.

Reduced saturated fattyacids Stearyl-COA desaturase

3-Ketoacyl-ACP synthase II

Acyl-ACP thioesterase

Yeast ,Polashock et al,

Castor, Bleibaum et al,

Soybean ,Yadav et al,1993

Reduced saturated fattyacids in

phosphatidylglycerol

Acyl-ACP:glycerol-3-phosphate

acyltransferase

Squash,Arabidopsis, Murata et al., 1992

lncreased saturated fattyacids in

phosphatidylglycerol

Acyl-ACP:glycerol-3-phosphate

acyltransferase

Escherichia coli ,Wolter et al, 1992.

Petroselinic acid production.Acyl-ACP desaturase Coriander ,Cahoon et al., 1992

Increased-a-linolenic acid w3 desaturase Arabidopsis, Arondel et al.,1992;Yadav etal.1993

Cyclopropane fatty acid Cyclopropane synthase Escherichia coli,Schmid1993

y-Linolenic acid production Linolenic Ab desaturase Synechocystis, Reddy et al., 1993

increased oleic acid production ACP:protein A fusion Spinach Lee et al., 1993

MODIFYING GENE FOR FATTYACID COMPOSITION

Understanding and manipulating the biochemistry of oil biosynthesis,and cloning of the genes encoding the enzymes involved in fatty acidmodification and oil accumulation

Produces "designer" plant seed oils with improved nutritional.

Includes overexpression or suppression of genes encoding single ormulti-step biosynthetic pathways

assembles the complete pathway for the synthesis of long-chainpolyunsaturated fatty acids.

transgenic plant oils represent the first success in design of modified plant products.

Directed gene down-regulation strategies have enabled the specific tailoring of

common fatty acids.

diacylglycerol acyltransferase 2, which catalyzes the final step in triacylglycerol

assembly, is an important contributor to the synthesis of unusual fatty acid.

increasing the accumulation of Δ12-modified fatty acids synthesized by transgenically

expressed FAD2-like enzymes is popular .

biochemical analysis of plants that express introduced fatty-acid metabolic pathway

ensures the removal of novel fatty acids from their site of synthesis on

phosphatidylcholine which enable further modification, exclusion from membrane

lipids and accumulation in seed triacylglycerols containing oils.

Some works done

Genetic modification now makes it possible to improve the composition and

properties of oils from different plants far more quickly and precisely.

The first genetically modified vegetable oil has a high proportion of lauric

acid - desirable for many food and non-food applications

Recently a new soybean has been developed, producing less saturated and

more heat stable oil, thus has a healthier fatty acid composition

Rapeseed oil is rich in monounsaturated fatty acids. But a different fatty acid

composition would be better for some applications.

Genetic engineering could be used to optimise the fatty acid composition of

rapeseed oil

Rapeseed can be used to produce certain emulsifiers, vitamin E, and substances

that can help lower cholesterol levels.

Genetically modified rapeseed could be developed with a higher content of

long-chain fatty acids as fatty acids with longer side chains remain solid at

higher temperatures.

There is a wide and diverse range of unusual fatty acids in the seed oil of many

wild plants. with unknown biological role, but may have a role in defence

against pests.

sources of these unusual fatty acids cannot be produced economically on a

commercial scale.

Hydroxy, epoxy, conjugated, acetylenic, very long chain, medium chain and

branched chain fatty acids and liquid waxes are among the industrial targets of

greatest interest.

Oils high in hydroxy fatty acids can be produced from castor and Lesquerella ,

but it could be produced more economically on a large scale currently with

canola or soybeans engineered with genes for such metabolism

Genes for most of these unusual fatty acids have been cloned.