Any comments?

Ludvig Mortberg Agneta.Guillemot at historia.umu.se
Sun Oct 15 13:46:02 EST 1995


Taken without permission from Biological Abstracts 
on CD-ROM, for "fair use" only:

TI: Molecular classification of living organisms.
AU: Saccone-C; Gissi-C; Lanave-C; Pesole-G
CS: Dip. Biochim. Biol. Mol., Univ. di Bari, via Orabona, 
4, 70126 Bari, Italy
SO: Journal of Molecular evolution 40(3): 273-279
PY: 1995
IS: 0022-2844
LA: English
AB: Recent studies in molecular evolution have 
generated strong conflicts in opinion as to how world 
living organisms should be classifed. The traditional 
classification of life into five kingdoms has been 
challenged by the molecular analysis carried out mostly 
on rRNA sequences, which supported the division of the 
extant living organisms into three major groups: 
Archaebacteria, Eubacteria, and Eukaryota. As to the 
problem of placing the root of the tree of life, the analysis 
carried out on a few genes has provided discrepant 
results. In order to measure the genetic distance between 
species, we have carried out an evolutionary analysis of 
the glutamine synthetase genes, which previously have 
been revealed to be good molecular clocks, and of the 
small and large rRNA genes. All the data demonstrate 
that archaebacteria are more closely related to 
eubacteria than to eukaryota, thus supporting tha 
classical division of living organisms into two main 
superkingdoms, Prokaryota and Eukaryota.
- - - 
JA: Biological Abstracts vol. 99 Iss. 11, ref. 155946
UD: 9502


TI: Root of the universal tree of life based on ancient 
aminoacyl-tRNA synthetase gene duplications.
AU: Brown-J-R; Doolittle-W-F
CS: Canadian Inst. Advanced Res., Dep. Biochem., 
Dalhousie Univ., Sir Charles Tupper Build., Halifax, NS 
B3H 4H7, Canada
SO: Procedings of the National Academy of Sciences of 
the United States of America 92(7): 2441-2445
PY: 1995
IS: 0027-8424
LA: English
AB: Universal trees based on sequences of single gene 
homologs cannot be rooted. Iwabe et al. (Iwabe, N., 
Kuma, K.-I., Hasegawa. M., Osawa, S. & Miyata, T. 
(1989) Proc. Natl. Acad. Sci. USA 86, 9355-9359) 
circumvented this problem by using ancient gene 
duplications that predated the last common ancestor of 
all living things. Their seperate, reciprocally rooted trees 
for elongation factors and ATPase subunits subunits 
showed Bacteria (eubacteria) as branching first from the 
universal tree with Archaea (archaebacteria) and 
Eukarya (eukaryotes) as sister groups. Given its topical 
importance to evolutionary biology and concerns about 
the appropriatness of the ATPase data set, an evaluation 
of the universal tree using other ancient gene 
duplications is essential. In this study, we derive a 
rooting for the universal tree using aminoacyl-tRNA 
synthetase genes, an extensive multigene family whose 
divergence likely preceded that of prokaryotes and 
eukaryotes. An approximatly 1600-bp conserved region 
was sequenced from the isoleucyl-tRNA synthetases of 
several species representing deep evolutionary branches 
of eukaryotes (Nosema lucustae), Bacteria (Aquifex 
pyrophilus and Thermotonga maritima) and Archae 
(Pyrococcus furiosus and Sulfolobus acidocaldarius). In 
addition, a new valyl-tRNA synthetase was characterized 
from the protist Trichomonas vaginalis. Different 
phylogenetic methods were used to generate trees of 
isoleucyl-tRNA synthetase rooted valyl- and leucyl-tRNA 
synthetases. All isoleucyl-tRNA synthetase trees show 
Archaea and Eucarya as sister groups, providing strong 
confirmation for the universal rooting reported by Iwabe 
et al. As well, there was strong support for synthetase 
gene from Tr. vaginalis clustered with other eukaryotic 
ValRS genes, which may have been transferred from the 
mitochondrial genome to the nuclear genome, 
suggesting that this amitochondrial trichomonad once 
harbored an endosymbiotic bacterium.
- - -
JA: Biological Abstracts vol. 99, Iss. 11, Ref. 151624
UD: 9502


I couldn't resist posting this. Sorry.

L.




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