Techniques for Cloning Plants

Asexual Reproduction and Transgenic Plant Culture

Finding the right genes

• Just like for animals and humans, once we find an individual plant with a desired trait, we can try to find the gene for that trait using gel electrophoresis and PCR.

• Examples of naturally occurring traits scientists might like to use include: genes for disease resistance and drought resistance.

Disease ResistanceSusceptible tree Resistant Tree

American Chestnut Restoration Project; US Forest Service; University of Tennessee; http://www.fs.fed.us/r8/chestnut/history.php; Last edited 4-30-2010; Accessed 1-03-2014.

Drought Resistance

Drought resistant Drought susceptible

Batra, Karen; “Biotech Corn Stands Tall;” BiotechNOW; http://www.biotech-now.org/food-and-agriculture/2012/08/biotechs-drought-tolerant-corn-stands-tall?utm_source=newsletter&utm_medium=email&utm_campaign=0808; 8-02-2012; Accessed 1-3-2014

Traits• Once the traits have been isolated, scientists

want to grow plants that have both the desired trait and all of the other good traits their strain has. For example – you wouldn’t want resistant corn or chestnuts that tasted bad.

• Traditional breeding, where each offspring has a mother and father, can bring in bad traits with the good ones.

• However, we can use biotech tools to see which organisms have the genes and which do not – we don’t have to wait for them to grow up.

Genetic engineering

• As with animals, we can use vectors to put the desired gene, with a marker, into plant cells.

• A vector that is often used by genetic engineers working with plants is a bacterium called agrobacterium.

• Natural agrobacterium already would work by injecting DNA into plant cells.

Cloning• Unlike with animals, plants respond very

naturally to being cloned. Plant clones occur in nature when a stem or leaf are buried in soil, they can develop roots from the stem of leaf and grow a new plant. Almost all plant cells can act as stem cells and produce other plant tissues.

• This is called vegetative propagation and has been used by farmers and gardeners for centuries.

• The new plant is genetically identical to the parent plant.

Vegetative Propagation

Meritnation; http://www.meritnation.com/ask-answer/question/what-is-vegitative-propagation/science/1759172; edited 10-2012; Accessed 1-3-2014.

In the lab:• Samples are often grown on a nutrient

medium, similar to the agar used to grow bacteria.

• The nutrient is different that bacterial media – it provides the plant minerals, nutrients and hormones that will help young plant clones grow.

• Hormones like auxins and cytokinins help the plant cells grow into young “plantlets” or baby plants.

Agrobacterium

iGEM 2010; Team Nevada/Agrobacterium Transformations; http://2010.igem.org/wiki/images/d/d0/Agro_theory.png; Accessed 1-3-2014.

In the lab:• Like when bacterial cultures were

grown – it is important to use sterile technique to prevent unwanted funguses or other cells from growing.

• Use sterilized tools, surfaces, media and clean plant samples.

• As with bacteria, you can use flame or steam sterilization for tools and use 70% alcohol or 10% bleach for surfaces.

• Avoid touching any samples or tools to anything that is not sterile – this includes you.

Plant tissue culture:

Biotech Hobbyist Magazine; http://www.nyu.edu/projects/xdesign/biotechhobbyist/tree_cloning.html; Accessed 1-3-2014.