BY:

Varsha chauhan

Genetically Modified crops

Genetic modification is modern biotechnology techniques to manipulate the genetic material of organisms within a species or between different species.

Transgenic plants are the results of modern biotechnology.

An organism containing a transgene introduced by technological methods is called transgenic.

Transgenes are the genetically engineered gene added to a species. The process of producing transgenic organism is called transgenesis .

PLANT TRANSFORMATION METHODS : Transfer of DNA via a vector: Agrobacterium Direct transfer of DNA: gene guns electroporation microinjection

Steps in genetic modification for plants

Golden rice

GOLDEN RICEGolden rice is a variety of rice (Oryza sativa)

produced through genetic engineering with improved nutritional quality.

Golden rice appears golden due to presence of B-carotene, a precursor of vitamin A in the edible portions of rice.

The concept of golden rice was developed by potrykus and beyerwith the goal of helping children and pregnant women who suffer from vitamin A deficiency (VAD) , which was a major source for 1-2 million deaths, 500,000 cases of irreversible blindness and millions of cases of xerophthalmia annually.

Growing and consuming golden rice could be an economical and effective way of overcoming these health problems, vis-à-vis oral or injecting vitamins A supplement due to its cost factor.

Golden rice was designed to produce beta-carotene, a precursor of vitamin A, in the edible part of rice, the endosperm.

The rice plant can naturally produce beta-carotene in its leaves, where it is involved in photosynthesis. However, the plant does not normally produce the pigment in the endosperm, where photosynthesis does not occur

HOW DOES IT WORK?

genetic engineering is used in order to create Golden Rice, where the method involved is by using a common plant bacterium which naturally inserts its genes into plant tissue hosts.

The addition of 2 genes in the rice genome will complete the biosynthetic pathway

1. Phytoene synthase (psy) – derived from daffodils ( Narcissus pseudonarcissus )Phytoene synthase is a transferase enzyme involved in the

biosynthesis of carotenoids. It catalyzes the conversion of geranylgerany pyrophosphate to phytoene.

2. lycopene cyclase (crt1) – from soil bacteria Erwinia uredovoraProduces enzymes and catalysts for the biosynthesis of

carotenoids ( β -carotene) in the endosperm

The psy and crt1 genes were transformed into the rice nuclear genome and placed under the control of an endosperm-specific promoter , so they are only expressed in the endosperm.

The exogenous lyc gene has a transit peptide sequence attached so it is targeted to the plastid , where geranylgerany diphosphate formation occurs.

The bacterial crt1 gene was an important inclusion to complete the pathway, since it can catalyze multiple steps in the synthesis of carotenoid, while these steps require more than one enzyme in plants.

The end product of the engineered pathway is lycopene , but if the plant accumulated lycopene, the rice would be red.

Recent analysis has shown the plant's endogenous enzymes process the lycopene to beta-carotene in the endosperm, giving the rice the distinctive yellow color for which it is named.

The original golden rice was called SGR1, and under greenhouse conditions it produced 1.6 µg/g of carotenoids.

DISADVANTAGEHealth

May cause allergies or fail to perform desired effectSupply does not provide a substantial quantity as the

recommended daily intakeEnvironment

Loss of Biodiversity. May become a gregarious weed and endanger the existence of natural rice plants

Genetic contamination of natural, global staple foodsCulture

Some people prefer to cultivate and eat only white rice based on traditional values and spiritual beliefs

Bt cotton is an insect resistant transgenic crop designed to combact the bolloworm infection of cotton.

It was created by genetically engineering the cotton genome to express an insecticidal protoxin produced by a bacterium bacillus thuringiensis.

The Bt is a short form Bacillus thuringiensis.The bacterium Bacillus thuringiensis (Bt) is a

family of over 200 different proteins which naturally produce chemicals harmful to selective insects, most notably the larvae of moths and butterflies, beetles, cotton bollworms and flies, and harmless to other forms of life.

This bacterium forms parasporal crystals during stationary phase of its growth cycle. The synthesized crystalline proteins called ‘endotoxins’ are highly toxic to certain insects.

They kill the insect by acting on the epithelium tissues of midgut of caterpillars.

These bt toxins includes cry I , cry II, cry III and about 200 others that accumulate within the bacterium body as an inactive precursor. (* cry = crystalline)

The gene coding for Bt toxin has been inserted into cotton, causing cotton to produce this natural insecticide in its tissues.

(Bt) cotton was created through the addition of genes encoding toxin crystals in the Cry group of endotoxin. When insects attack and eat the cotton plant the Cry toxins are dissolved.

This is made possible due to the high pH level of the insects stomach. The now dissolved and activated Cry molecules bond to cadherin-like proteins on cells comprising the brush border molecules.

Due to the formation of Cry ion channels sufficient regulation of potassium ions is lost and results in the death of epithelial cells. The death of such cells creates gaps in the brush border membrane. The gaps then allow bacteria and (Bt) spores to enter the body cavity resulting in the death of the organism.

The major advantage of Bt cottonThe Bt cotton has inbuilt genetic resistance to bollworms and is

very effective in controlling the yield losses caused by bollworms to a considerable extent. The resistance is governed by a single dominant gene.

Use of Bt cotton reuces use of pesticides resulting in reducing the cost of cultivation.

It results in improvement of yield levels and also improves margin of profit to the farmers.

It provides opportunities to grow cotton in areas of severe bollworm incidence.

It promotes ecofriendly cultivation of cotton .It also reduces environmental pollution and risk of health

hazards associated with use of insecticides because in Bt cotton the insecticides are rarely used. An average reduction of 3.6 sprays per crop season has been reported in Bt varieties as compared to non-Bt.

Effect of Bt cotton on the health of animals, poultry, human and environmentThe feeding of Bt cotton seed to animal has not been

reported to have any adverse effect.Seed of Bt cotton and its cake do not have any

adverse effect on digestion of animals. Moreover, no allergic or toxic effect of use of Bt cotton seed and meal has been reported.

The oil extracted from the seed of Bt cotton has not been found to have any adverse effect on human health.

No adverse effect of Bt cotton has been reported on non target beneficial insects so far.

No adverse effect of Bt cotton on the environment has been reported by any of the countries where Bt cotton is commercially cultivated.

Thankyou