Subject: Re: endosymbiotic theory

From: [email-masked] (Jonathan B. Marder)
Date: Tue, 03 Dec 96 10:01:32 GMT

In article <[email-masked]>,
   [email-masked] wrote:
>I am researching why there are different types of chlorplasts (membranes
>and pigments) in algae and terrestrial plants and was wondering if anyone
>had a good simple explanation as to why.  This is for general introductory
>purposes.  I understand the reasoning behind the endosymbiotic theory but
>there are still such differences.
>
>Brian 

This is a really interesting question. Chloroplasts of terrestrial plants and 
green algae are apparently related to prokaryotes like Prochloron or 
Prochlorothrix. These bacteria have chlorophylls a and b but no 
phycobilisomes.

The situation is different for rhodophytes (red algae) where the plastids 
(rhodoplasts) appear to be like cyanobacteria i.e. they have no chlorophyll b,
but do have phycobilisomes. This is also true for Cyanophora paradoxa, a 
eukaryote with a cyanobacterium-like plastid.

Thus we have evidence for at least two types of plastid pointing to two 
separate endosymbiotic events in evolution.

BTW It seems that relatives of purple non-sulphur photosynthetic bacteria also 
found their way into eukarotes, but lost their photosynthetic capacity. It is 
to this bacterial group that mitochondria are most closely related. 

Jonathan B. Marder             ,      Department of Agricultural Botany
E-mail: [email-masked] |      The Hebrew University of Jerusalem
Phone: (08 or +9728) 9481918   | /\/  Faculty of Agriculture
Fax:   (08 or +9728) 9467763   |/  \  P.O.Box 12, Rehovot 76100, ISRAEL
     http://www.agri.huji.ac.il/~marder