Transgenic Rice Plants Essay Research Paper The

Transgenic Rice Plants Essay, Research Paper

The following form contents were entered on 15th Apr 97

Date = 15 Apr 97 23:58:50

subject

= School Sucks

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name = Sarah

Lenhardt

email = sxl63@po.cwru.edu

publish = yes

subject = Biology

title

= Transgenic Rice Plants

papers = Please put your paper here.

Transgenic

Rice Plants that Express

Insect Resistance

For centuries, rice has been

one of the most important staple crops for the world and it now currently feeds

more than two billion people, mostly living in developing countries. Rice

is the major food source of Japan and China and it enjoys a long history of

use in both cultures. In 1994, worldwide rice production peaked at 530 million

metric tons. Yet, more than 200 million tons of rice are lost each year to

biotic stresses such as disease and insect infestation. This extreme loss

of crop is estimated to cost at least several billion dollars per year and

heavy losses often leave third world countries desperate for their staple food.

Therefore, measures must be taken to decrease the amount of crop loss and

increase yields that could be used to feed the populations of the world. One

method to increase rice crop yields is the institution of transgenic rice plants

that express insect resistance genes. The two major ways to accomplish insect

resistance in rice are the introduction of the potato proteinas

e inhibitor

II gene or the introduction of the Bacillus thuringiensis toxin gene into the

plant’s genome. Other experimental methods of instituting insect resistance

include the use of the arcelin gene, the snowdrop

lectin/GNA (galanthus nivallis

agglutinin) protein, and phloem specific promoters and finally the SBTI gene.

The introduction of the potato proteinase inhibitor II gene, or PINII,

marks the first time that useful genes were successfully transferred from a

dicotyledonus plant to a monocotyledonous plant. Whenever the plant is wounded

by insects, the PINII gene produces a protein that interferes with the insect’s

digestive processes. These protein inhibitors can be detrimental to the growth

and development of a wide range of insects that attack rice plants and result

in insects eating less of the plant material. Proteinase inhibitors are of

particular interest because they are part of the rice plant’s natural defense

system against insects. They are also beneficial because they are inactivated

by cooking and therefore pose no environmental or health hazards to the human

consumption of PINII treated rice.

In order to produce fertile transgenic

rice plants, plasmid pTW was used, coupled with the pin 2 promoter and the

inserted rice actin intron, act 1. The combination of the pin 2 promoter and

act 1 intron has been shown to produce a high level, wound inducible expression

of foreign genes in transgenic plants. This was useful for delivering the

protein inhibitor to insects which eat plant material. The selectable marker

in this trial was the bacterial phosphinothricin acetyl transferase gene (bar)

which was linked to the cauliflower mosaic virus (CaMV) 35S promoter. Next

the plasmid pTW was injected into cell cultures of Japonica rice using the

BiolisticTM particle delivery system. The BiolisticTM

system proceeds as

follows:

Immature embryos and embryonic calli of six rice materials were

bombarded with

tungsten particles coated with DNA of two plasmids containing

the appropriate

genes.

The plant materials showed high frequency

of expression of genes when stained

with X-Gluc. The number of blue

or transgenic units was approximately 1,000.

After one week, the transgenic

cells were transferred onto selection medium

containing hygromycin

B. After two weeks, fresh cell cultures could be

seen on bombarded

tissue. Some cultures were white and some cultures were blue.

Isolated cell

cultures were further selected on hygromycin resistance. However,

no

control plant survived.

Then twenty plates of cells were bombarded with

the PINII gene, from which over two hundred plants were regenerated and grown

in a greenhouse. After their growth, they were tested for PINII gene using

DNA blot hybridization and 73% of the plants were found to be transgenic.

DNA blot hybridization is the process by which DNA from each sample was digested

by a suitable restriction endonuclease, separated on an aragose gel, transferred

to a nylon membrane, and then finally hybridized with the 1.5 kb DNA fragment

with pin 2 coding and 3′ regions as the probe. The results also indicate that

the PINII gene was inherited by offspring of the original transgenic line,

that the P

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