From: jlogsdon@sunflower.bio.indiana.edu (John Logsdon)
Subject: Re: Eukaryotes w/o mitochondria (was Re: The evolution of sexes)
Organization: Indiana University
Date: Thu, 30 Jul 92 17:08:20 GMT

In article <785@tdat.teradata.COM>, swf@teradata.com (Stanley Friesen) writes:
> 
> In article <1992Jul28.230849.16222@bronze.ucs.indiana.edu> jlogsdon@sunflower.bio.indiana.edu (John Logsdon) writes:
> |
> |First of all there are LOTS of eukaryotes (in addition to _Pelomyxa_)
> |that do not have organelles,that is chloroplasts(cp) and/or mitochondria(mt).
> |...
> | Since mt arose
> |prior to the endosymbiosis of cps, mts are the only organelle really in issue
> |here. (But see Palmer, Current Biology, 1992, v2: pp 318- 320 for evidence 
> |that cps may have arisen deeper in eukaryotic evolution than once thought). 
> 
> Well, you seem to have more up-to-date knowledge in this area than I do.
> I am having enough trouble staying up to date in paleontology, so I have
> not been following protistology since Dr. Eugene Bovee retired.
> 
> I'm not to surprised about evidence for early origin of cps, since I know
> they have originated at least 4 distinct times.
>
Actually it is still unsettled as to whether plastids (chloroplasts being a 
particular type) are Monophyletic (a single origin) or Polyphyletic (multiple 
origins). See Gray, MW Trends in Genetics v5: pp294-299 (1989). 

> 
> I thought I had heard of someone finding DNA in ciliary basal bodies.
> Has this been refuted?  (Mind, I never did like Margulis' idea of
> spirochetes as pre-cilia, but this does not mean that some other,
> otherwise unknown, group of prokaryotes might not be the source of cilia).

You are correct that it was claimed that basal bodies contained DNA in 
_Chlamydomonas_ (Cell v59: pp121-132 (1989)).  Unfortunately, there have
been a number critiques of this paper, two papers which I have at hand:

1) Critique based on the physical (size) limitations of the basal bodies 
and the fact that Anti-DNA antibodies do not stain the "organelles"
(Cell v62:615-619(1990)).
 
2) Critique based on the apparent copy number of the genetic linkage
group that was purpored to be the basal body DNA. The copy number is
the same as other nuclear linkage groups, and is apparently unchanged 
in mutants which lack basal bodies (J. Cell Biology v113: 339-346 (1991)).

In addition, my feeling, garnered second-hand from a friend in the Chlamy 
community, is that the original reports are in serious doubt.
  
> 
> |More on the issue of euks w/o mts: Tom Cavalier-Smith wrote a nice "News and
> |Views" article a few years back (Nature, 1987, v326:332-333) in which he
> |recognizes at least FOUR major groups of eukaryotic protists w/o mts. 
> |Archamoebae (to which _Pelomyxa_ belong),  Metamonada (which includes the 
> |diplomonad _Giardia_), Microsporidia (includes _Vairimorpha_), and Parabasalia
> |(ie:_Trichomonas_).
> 
> An impressive list.  The diplomonad and the parabasalian surprize me.
> Or are the diplomonads considered to be derived from parabasalians?
> Or is it only Giardia amoung the diplomonads that lacks mts?

As you probably know, protist systematics (non-molecular) is pretty messy 
(At least at the level of relationships between major protist groups);
much like that of early bacterial systematics (pre-Woese).

Cav.-Smith considers Metamonada, Parabasalia, Microsporidia and Archamoebae 
to be separate Phyla, all of whose members are amitochondrial (ie:diplomonads,
in Class Anaxostylea, are ALL amitochondrial). _Trichomonas_ (Parabasalian)
_Giardia_ (Metamonadan), and _Vairimorpha_ (Microsporidian) branch off quite
separately on the rRNA tree, also supporting them as separate "Phyla."
(see ref below).

> 
> |These Phyla (at least the last three, for which there are
> |data) branch off of the main eukaryotic line of descent very early - BELOW 
> |organisms known to have mitochondria (ie:trypanosomes). This is
> |based on ribosomal RNA (and in some cases, protein) sequences. This led Cav.-
> |Smith to state "..some of these protozoa are living relics of the earliest 
> |phase of eukaryote cell evolution and diverged from our own anscestors before 
> |the symbiotic origin of mitochondria (ref above)." The current data also 
> |support this contention.
> 
> This certainly sounds reasonable to me.  If indeed the rRNA and protein
> sequences support the early branching, I would consider the matter just
> about settled.
> 

In fact, in a more careful look at the literature, a member of the Archamoebae,
_Entamoeba_ has had the rRNA sequenced (Sogin, Curr. Opin. Genet. Devel. 
v1: pp457-463).  It branches off Above the trypanosomes, so therefore may have
primitively had mt, and subsequently lost them.  It is not clear whether the
phylum Archamoebae is not monophlyetic, and some other members may branch off
nearer Giardia and the like, or some other scenario(s). More organisms in
Archamoebae need to be looked at to address this question (to my knowledge
_Pelomyxa_ has nott been looked at).
 
> |Is there any evidence for sex in these primitively mt- organisms?
> 
> I have never heard of sex in Pelomyxa.
> I am not sure about microsporids, since they are so different from
> the Sporozoa proper (which do have sex).

Therefore, it still seems to me an open question as to whether amitochondrial
 organisms (primitively, or secondarily) have sex!

> 
> -- 
> sarima@teradata.com			(formerly tdatirv!sarima)
>   or
> Stanley.Friesen@ElSegundoCA.ncr.com
> 
John
__________________________________________________________
John Logsdon         Department of Biology
                     Indiana University
                     Bloomington, IN  47405
                     (812) 855-2549
                     (812) 855-6705 fax

jlogsdon@sunflower.bio.indiana.edu
____________________________________________________________