Paul Lepp asks,
"A few months ago there was a discussion here about phylogenies based
on heat shock proteins and a number of other proteins. From what I
remember it seemed that the argument was made that eukaryotes could
have arisen from the fusion of a gram pos. and an archea. Could
someone be so kind as to pass along a few cites on the HSPs and the
gram pos./archea connection. Much appreciated."
Gupta and Golding (1993) have noted that the sequences of archaebacterial
HSP70 genes most closely resemble those from gram positive bacteria. The
dendrogram of HSP70 genes is not consistent with the Three Domain Hypothesis
of Woese. They point out that there are many other gene dendrograms that
also reveal a close relationship between archaebacteria and gram positive
bacteria in spite of widespread belief that the archaebacteria form a
separate monophyletic group.
In order to preserve the Three Domain Hypothesis in the face of such
evidence, Gupta and Golding (1993) postulate that eukaryotes arose from a
fusion between an achaebacterial and a gram *negative* ancestor. Thus,
according to these authors, some eukaryotic genes are more similar to
archaebacterial genes while others (such as HSP70 genes) are more similar to
genes from gram negative bacteria.
Of course, another possibility is that the Three Domain Hypothesis is wrong
and the HSP70 dendrogram is a true representation of the actual species
phylogeny. I should point out that the eukaryotic HSP70 genes are, in
fact, no more similar to those from gram negative bacteria than to genes
from other bacteria.
Hope this helps.
Laurence A. Moran (Larry)
Gupta, R.S. and Golding, G.B. (1993) Evolution of HSP70 gene and its
implications regarding relationships between archaebacteria, eubacteria,
and eukaryotes. J. Mol. Evol. 37, 573-582.
Boorstein, W. R., Ziegelhoffer, T. and Craig, E.A. (1994) Molecular evolution
of the HSP70 multigene family. J. Mol. Evol. 38, 1-17.
Rensing, S.A. and Maier, U.-G. (1994) Phylogenetic analysis of the stress-70
protein family. J. Mol. Evol. 39, 80-86.