Plastid DNA question

Subbaiah C. Chalivendra subbaiah at
Mon Sep 4 14:17:14 EST 2000

Dana A. Dudle  wrote:
>  I have never heard of any work on the genomes of other plastids.
>Is this because chloroplasts are more easily extracted, or more abundant
>in plant cells than in other plastids?  Is the DNA lost from these other
>kinds of plastids? Are there fewer copies of the plastid chromosome in
>amyloplasts (for example) than in chloroplasts?  Have I just missed
discussion of alternate plastid DNA in the literature?

Chloroplasts are one type of plastids specialized to do 
photosynthesis, just like chromoplasts or amyloplasts which have 
different functions. In many cases they are inter-convertible. 
Therefore, other plastid types in a particular species should have 
the same plastome (plastid genome) component (gene content as well as 
copy number). However, expression patterns of plastid genes and 
import of cytoplasmic proteins (nuclear encoded) differ from one type 
to the other in order to serve different functions. For example, 
during the transition of chloroplasts in the pericarp of developing 
fruits (e.g., tomato, sweet pepper) to chromoplasts as the fruits 
ripen, show different mRNA and protein profiles. Studies indicate 
that mechanisms such as DNA methylation or RNA/protein turnover may 
play a role in the differential gene expression, without any 
alterations in the plastome.

However, plastids in parasitic plants (which do not carry out 
photosynthesis) have been shown to have lost a part of the plastome 
(perhaps genes that have no function).

Jeffrey D. Palmer at Indiana University, Bloomington, an authority on 
plant organellar genomes, would have more details.

Subbaiah Chalivendra

Subbaiah Chalivendra, Ph. D.
S-27 Turner Hall
Dept. Crop Sciences, 1102 S. Goodwin Ave
University of Illinois
Urbana, IL 61801-4730

Phone: 217 333-9743

Fax:   217 333-6064


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