from
http://opbs.okstate.edu/~melcher/MG/MGW1/MG1378.html :
-The RNA polymerases of organelles resemble those of eubacteria more than they do those of eucaryotes. Bacterial and organelle polymerases are sensitive to the same inhibitors and insensitive to inhibitors of eucaryotic RNA polymerases.
-Organelle protein synthesis is sensitive to the same inhibitors that inhibit protein synthesis in eubacteria and insensitive to some that inhibit cytoplasmic protein synthesis. Organelle and bacterial ribosomes are more similar to each other than either are to cytoplasmic ribosomes of eucaryotes.
-Phylogenetic analysis of small subunit rRNA nucleotide sequences suggested that mitochondrial rDNA shared a common ancestor with modern endosymbiotic bacteria (ricketsia, Agrobacterium, Rhizobium).
-Similarly, 16S rDNA phylogenetic analysis suggests that most plastid rDNA genes shared common ancestors with a cyanobacterium. Euglena and Chlamydomonas rDNAs probably arose from a different ancestral cyanobacterial rDNA..
-Intrageneric comparisons of organelle genomes reveal some species with the same gene in both organelle and nuclear genomes. One or the other may be inactive. Occasionally an active gene may be in the organelle for one species and in the nucleus for another of the same family.
from
http://en.wikipedia.org/wiki/Endosymbiotic_hypothesis :
Evidence that mitochondria and chloroplasts arose via an ancient endosymbiosis of a bacteria is as follows:
-Both mitochondria and chloroplasts contain DNA which is fairly different from that of the cell nucleus, and in a quantity similar to that of bacteria. Further, they are surrounded by two or more membranes, and the innermost of these shows differences in composition compared to the other membranes in the cell. This is consistent with a cellular origin.
-New mitochondria and chloroplasts are formed only through a process similar to binary fission. In some algae, such as Euglena, the chloroplasts can be destroyed by certain chemicals or prolonged absence of light without otherwise affecting the cell. In such a case, the chloroplasts will not regenerate.
-Much of the internal structure and biochemistry of chloroplasts, for instance the presence of thylakoids and particular chlorophylls, is very similar to that of cyanobacteria. Phylogenies built with bacteria, chloroplasts, and eukaryotic genomes also suggest that chloroplasts are most closely related to cyanobacteria.
DNA sequence analysis and phylogeny suggests that nuclear DNA contains genes that probably came from the chloroplast.
-Some genes encoded in the nucleus are transported to the organelle, and both mitochondria and chloroplasts have unusually small genomes compared to other organisms. This is consistent with an increased dependence on the eukaryotic host after forming an endosymbiosis.
-Chloroplasts appear in very different groups of protists, which are in general more closely related to forms lacking them than to each other. This suggests that if chloroplasts originated as part of the cell, they did so multiple times, in which case their close similarity to each other is difficult to explain.
What is wrong with this evidence ? How would you interpret it differently ?
