Phylogenetic adaptation of plastid DNA in the evolution of the heterotrophic euglenoid flagellate Astasia longa
Hachtel, W.
Botanisches Institut der Universität Bonn, Kirschallee 1, D-53115 Bonn, Germany
The colourless, nonphotosynthetic protist Astasia longa is phylogenetically related to green Euglena gracilis. The 73 kb plastid DNA (ptDNA) of A. longa is about half the size of E. gracilis chloroplast DNA (cpDNA). More than 50 kb of Astasia ptDNA sequence has been determined. No genes for photosynthetic function have been found except rbcL. Identified genes include rpoB, tufA, and genes coding for 3 rRNAs, 17 tRNAs, and 14 ribosomal proteins. Not only is the nucleotide sequence of these highly conserved between A. longa and E. gracilis, but a number of these genes are clustered in a similar fashion and have introns in the same positions in both species. There are strong arguments in favor of the A. longa ptDNA being functional. The results further support the idea that photosynthetic genes normally encoded in cpDNA have been preferentially lost in Astasia, but the chloroplast genes coding for components of the plastid translational apparatus have been maintained. This apparatus might be needed for expression of rbcL and also of still unidentified nonphotosynthetic genes of Astasia ptDNA.
Hachtel, W. (1996) DNA and gene expression in nonphotosynthetic plastids. In: M. Pessarakli, ed., Handbook of Photosynthesis. M. Dekker, New York, pp. 349-355
Hachtel, W. (1997) A plastid genome in the heterotrophic flagellate Astasia longa. Endocytobiosis and Cell Res., in press
| LOCATION |
DATE |
TIME |
| Lecture Hall I |
Sunday, April 5 |
04:30 pm |