WhatEntamoeba histolytica andGiardia lamblia tell us about the evolution of eukaryotic diversity |
| |
Authors: | J Samuelson |
| |
Institution: | (1) Department of Immunology and Infectious Diseases, Harvard School of Public Health, 665 Huntington Avenue, 02115 Boston, MA, USA |
| |
Abstract: | Entamoeba histolytica andGiardia lamblia are microaerophilic protists, which have long been considered models of ancient pre-mitochondriate eukaryotes. As transitional
eukaryotes, amoebae and giardia appeared to lack organelles of higher eukaryotes and to depend upon energy metabolism appropriate
for anaerobic conditions early in the history of the planet. However, our studies have shown that amoebae and giardia contain
splicoeosomal introns, ras-family signal-transduction proteins, ATP-binding casettes (ABC)-family drug transporters, Golgi,
and a mitochondrion-derived organelle (amoebae only). These results suggest that most of the organelles of higher eukaryotes
were present in the common ancestor of all eukaryotes, and so dispute the notion of transitional eukaryotic forms. In addition,
phylogenetic studies suggest many of the genes encoding the fermentation enzymes of amoebae and giardia derive from prokaryotes
by lateral gene transfer (LGT). While LGT has recently been shown to be an important determinant of prokaryotic evolution,
this is the first time that LGT has been shown to be an important determinant of eukaryotic evolution. Further, amoebae contain
cyst wall-associated lectins, which resemble, but are distinct from lectins in the walls of insects (convergent evolution).
Giardia have a novel microtubule-associated structure which tethers together pairs of nuclei during cell division. It appears
then that amoebae and giardia tell us less about the origins of eukaryotes and more about the origins of eukaryotic diversity. |
| |
Keywords: | Cyst wall evolution lateral gene transfer mitochondrion-derived organelle phylogeny |
本文献已被 SpringerLink 等数据库收录! |
|