Plant Biotechnology

butterbeanscubaΒιοτεχνολογία

12 Δεκ 2012 (πριν από 4 χρόνια και 10 μήνες)

287 εμφανίσεις

Plant Biotechnology

Chapter 6

Motivation for genetically
engineered crops


Agriculture is the biggest industrial sector
in the world


$1.3 trillion of products/year


Over past 40 years, world population has
doubled while agricultural land area has
increased by only 10%

Plant transgenics


Transfer of genes to plants directly
accelerates selective breeding practices
used in the past.


Cotton fiber strength


increased 1.5% per year through conventional
breeding


Increased 60% by inserting a single gene into the
plant


Corn and soybean have been targets of much
genetic engineering


Cloning


Many types of plants can regenerate from a
single cell, similar to a bacterium.


The resulting plant is a clone or replica of
plant from which original cell was taken.


Protoplast fusion


Introducing a gene into a “denuded” plant cell
and generating a new plant

Genetic engineering techniques
applied to plants

Protoplast fusion

Agrobacterium tumefaciens
as a vector for
transferring foreign genes into plant
chromosome


This bacterium naturally infects plant cells
causing cancerous growths
-

crown gall
disease


Infection (
vir
) genes carried on Ti plasmid

Infection Process


Vir genes copy T
-
DNA


Open channel in bacterial
cell membrane for T
-
DNA
to pass through


T
-
DNA enters plant through
wound, integrates itself into
plant chromosome

http://www.bio.davidson.edu/people/kabernd/seminar/2002/method/dsmeth/ds.htm

Leaf fragment technique used to
introduce foreign genes into plant


Small discs are cut from plant leaf


Discs are cultured to start a new plant


Early in the regeneration process, the bacterium
Agrobacterium tumefaciens

carrying a Ti
plasmid is introduced into the culture


The plasmid DNA combines with the plant
chromosome


Discs are treated with hormones to encourage
shoot and root development and then the new
plant is planted in the soil


Make leaf discs

Briefly culture

discs with

genetically

modified

Agrobacterium

Transfer to filter

paper over nurse

cells


Culture 2
-
3 days

Transfer to shoot stimulating medium

Leaf fragment technique

Agrobacterium

with Ti plasmid

with foreign gene

Gene guns

Gene

gun

Antisense technology


Used to produce the Flavr
-
Savr tomato in
1994.


Enzyme polygalacturonase breaks down
structural polysaccharide pectin in wall of a
plant.


This is part of the natural decay process in a
plant


Monsanto identified the gene than encodes
the enzyme and made another gene that
blocked the production of the enzyme.

Antisense molecules

Plant vaccines


Plants are susceptible to diseases caused
by viruses (tobacco mosaic virus)


Virus surface protein induces an immune
response in the plant against the
protein/virus


Researchers inserted the virus protein into
the plant genome using the Ti plasmid/
Agrobacter

vector for insertion and
expression in the plant

Concerns about genetically
modified foods


Human health


Unsuspected allergens


What other issues are there?


Environment


Messing up the gene pool of non
-
target
species in the environment


Lateral gene transfer


Still poorly understood in nature

Summary


Variety of techniques are available to
introduce genes into plants and have the
plants express the gene


Such genetic engineering is used to


Improve disease resistance


Flavor of product


Nutrition of product


Shelf life of product


Any other property of plant that improves its
value