WHAT

 
 
 

WHO

 
 
 

WHY

 
 
 

 Plastid Transformation in Crop Plants
 

WHAT ARE PLASTIDS? AND WHY IS IT USEFUL TO TRANSFORM THEM?

Plastids develop from proplastids which are small organelles found in the plant cell. 
Several kinds of plastid e.g. chloroplasts, chromoplasts and leukoplasts develop 
from the proplastid and each have a different function. The most common plastid 
found in the plant cell is the chloroplast.  There can  be up to several  hundred 
chloroplasts in a cell. 

CHLOROPLASTS TRAP THE SUNS ENERGY 

The main function of the chloroplast  is to harness the energy from sunlight and 
use it  to convert carbon dioxide and water to sugars that can used or stored by 
the plant. This process is known as photosynthesis.  Most chloroplast functions 
are dictated  by genes in  the nucleus.The chloroplast itself contains a circular 
molecule of DNA that also encodes genes for photosynthesis and other chloroplast 
activities.

POLLEN DOES NOT CARRY CHLOROPLAST DNA

One striking feature of plastids is that its genome (the circle of DNA) is maternally 
inherited in most plants.  This means that the pollen grains (the male reproductive
cells carry the genetic information contained in the nucleus but not in the chloroplast. 
This fact can be exploited in the context of genetic modification (GM) of plant 
species.  One of the main concerns of those opposed to GM technology is the
containment of the modified gene within the transgenic crop.  It is argued that 
there would be no control on the escape of  novel genes via  pollen dispersion. 
If  however, using  this technology,  the novel genes  were contained in the 
chloroplast,  the pollen grains would  remain  "unmodified" and so pose no 
threat of spread of the novel gene by pollen dispersion.
 
 

Contract no: QLK3-CT-1999-00692
Coordinator: Prof. Phil Dix, Department of Biology, NUI Maynooth, Co. Kildare, Ireland. 

Any questions? Email:phil.dix@may.ie
 
Chloroplast image from:   www.brigadoon.com/~schafer/biology/chloropl.html