Thylakoid Biogenesis and Dynamics: The Result of a Complex Phylogenetic Puzzle

Eukaryotic genome evolution: rearrangement and coevolution of compartmentalized genetic information

“…It posed questions about the underlying structures (along with X-ray crystallography), their function and biogenesis, as well as the evolution of the photosynthetic machinery, that were not previously accessible to a meaningful experimental analysis. The results obtained are fundamental (Herrmann 1996;Herrmann & Westhoff 2001).…”

“…These rearrangements must have been massive, frequent, with diverse kinetics and time-scales, and unexpectedly complex. They included four processes that operate in parallel and are probably of equivalent quality: intracellular transfer of DNA fragments/ genes, loss of (redundant or dispensable) genes, and gain of genetic information, either by reshuffling existing information or by lateral gene transfer (Herrmann 1997;Herrmann & Westhoff 2001). Genome shaping has been accompanied by: (ii) an intermixing of the endosymbiotic genetic potentials, but also by lateral gene transfer; (iii) the establishment of an integrated genetic machinery (rather than semiautonomous organelles); (iv) the generation of nuclear regulatory dominance; (v) a reductive evolution of organelle genomes, and, in a 'second step' of the evolution of eukaryotes, by (vi) the generation of spatiotemporal programs to manage complex multicellular societies.…”

“…Therefore, most, if not all, were transferred early in evolution. However, transfer of genes for complex organelle structures occurred gradually, with a non-stochastic selection, and, to retain function, unidirectionally (Herrmann & Westhoff 2001). Such structures are therefore genetic mosaics, of dual genetic origin, and their biogenesis requires the coordinated operation of genetic information and protein syntheses in different cellular spaces.…”

“…Such structures are therefore genetic mosaics, of dual genetic origin, and their biogenesis requires the coordinated operation of genetic information and protein syntheses in different cellular spaces. Chloroplasts contain at least eight major structures of dual genetic origin, including components of the photosynthetic machinery (thylakoid membrane, ribulose bisphosphate carboxylase/oxygenase), 70S ribosome, PEP-RNA polymerase, acetyl coenzyme-A carboxylase, Clp protease, transcript processing machinery, and inner envelope; the phylogenetically older mitochondria contain less (Herrmann & Westhoff 2001). The comparison of plastids, mitochondria and hydrogenosomes, their generally DNA-lacking derivatives, suggests that the 'ultimate aim of genome restructuring in the plant cell, as in the eukaryotic cell in general, is the elimination of genome compartmentation while retaining physiological compartmentation' (Herrmann & Westhoff 2001).…”

“…It is by no means trivial to say that the photosynthetic process in chloroplasts is anchored in the genetic system of the plant (autotrophic eukaryotic) cell, which has a compartmentalized set-up with a long and complex history. Molecular research in photosynthesis has contributed substantially to the elucidation of the basic principles of the genetic system of that cell, to formulate a new concept of eukaryotism from both functional and phylogenetic aspects, and to develop the currently predominating concept of 'molecular phylogeny' towards a 'functionally defined molecular phylogeny' (Herrmann 1997;Martin & Herrmann 1998;Race et al 1999;Herrmann & Westhoff 2001) that we ultimately want to understand. Although mere sequence analysis has been, and is, useful for the deduction of genealogies, evolution is based on selection of function, and without knowledge of the underlying functional aspects, so far it has revealed neither how and why a particular development has occurred, nor how the plant cell operates.…”