Article

Chloroplasts of most vascular plants contain a NADH dehydrogenase complex (Ndh complex) homologous to the mitochondsial complex I. Eleven ndh genes encoding this complex are local- ized in the chloroplast genome. These genes are not present in the chloroplast genomes of several genera of free-living green algae (Chlorella, Chlamydomonas). but they occur in others (Nephroselmis, Mesosiigma, Chaeiosphaeridium). The Ndh complex in vaseular plants is involved in the protection against photo-oxidative stress. We have isolated Trebouxoid photo- bionts from Ramalina farinacea L. (Ach.) in order to study the possible presence and function of the Ndh complex in lichenized algae. PCR amplification and sequencing of DNA isolated from purified Trebouxoid photobionts indicates the presence of the ndhF gene in these algae. Its expression was confirmed by immunological analysis. The sequence presented a high degree of similarity with the previously described ndhD sequence of Physcomitrella patens subsp. patens, a moss which is used as an alternative model system to investigate the molecular basis in terrestrial plants. The homology was lower when compared with Anthoceros formosae, the fern Huperzia lucidula or the unicellular green alga Nephroselmis olivacea. These results clearly indicate the presence of the ndhD gene in Trebouxoid photobionts from Ramalina furinacea. They also suggest the possibility of a closer proximity of these Trebouxia plastid genome (o the Bryophytes and/or the Pteridophytes included in the Lycopodiales -immediate ancestors of land plants- than to other green algae lineages.