DNA is present in the nucleomorph of cryptomonads: Further evidence that the chloroplast evolved from a eukaryotic endosymbiont |
| |
Authors: | Martha Ludwig Sarah P. Gibbs |
| |
Affiliation: | (1) Department of Biology, McGillUniversity, 1205 Avenue Docteur Penfield, H3A 1B1 Montreal, Quebec, Canada |
| |
Abstract: | Summary The nucleomorph is a unique self-replicating organelle which is invariably present in the periplastidal compartment of cryptomonads. The nucleomorph ofCryptomonas abbreviata is located in a groove on the inner face of the pyrenoid. When JB-4-embedded sections ofC. abbreviata are stained with 4-6-diamidino-2-phenylindole (DAPI), the nucleomorph exhibits a blue fluorescence characteristic of DNA-DAPI complexes. This fluorescence is removed by DNase digestion, but not by RNase. When cells are prepared for electron microscopy by the method of Ryter and Kellenberger (Schreil 1964), a network of fine DNA-like fibrils is observed in the nucleomorph matrix. It is estimated that the nucleomorph contains between 108 and 109 daltons of DNA. The presence of DNA in nucleomorphs strongly supports the hypothesis that the nucleomorph is the vestigial nucleus of a eukaryotic endosymbiont. It is postulated that this eukaryotic symbiont was an ancestral red alga or an organism closely related to red algae. The cryptomonad host cell, on the other hand, is not evolutionarily close to any other group of algae. |
| |
Keywords: | Algal evolution Chloroplast evolution Cryptomonasabbreviata Nucleomorph DNA |
本文献已被 SpringerLink 等数据库收录! |
|