Nouveaux types d'ultrastructure plastidiale chez les Phéophycees

Systematics and evolutionary history of pyrenoid-bearing taxa in brown algae (Phaeophyceae)

“…However, several authors strongly suspect A. australe to be conspecific with A. ferruginea (Dele´pine & Asensi, 1975;Womersley, 1987;Mu¨ller & Parodi, 1994) and this is supported by the fact that both species exhibit similar tubular invaginations in their pyrenoids (Dele´pine et al, 1976;Tanaka et al, 2007). We therefore consider it reasonable to propose a new family of Scytothamnales, the Asteronemataceae, on the basis of our data on A. ferruginea (see Taxonomic changes).…”

“…Subsequent studies overlooked Mu¨ller et al's (1998) suggestion and followed the earlier, morphology-based arguments of Dele´pine & Asensi (1975), Dele´pine et al (1976), Magne (1976) and Asensi et al (1977), according to which Bachelotia and Asteronema could not be closely related because of their structural and ultrastructural differences (such as the apical versus lateral position of the pyrenoid in B. antillarum and A. ferruginea). Hence, when recent studies by Uwai et al (2005) and Phillips et al (2008) showed tree topologies where Bachelotia appeared closely related to the Scytothamnales -though without high support -the possibility of classifying them together was not discussed.…”

“…First, it has been reported previously that the three genera of the Scytothamnales sensu Peters & Clayton (1998) (Peters & Clayton, 1998;Tanaka et al, 2007) and A. ferruginea (Tanaka et al, 2007) all have tubular invaginations of the plastid envelope inside the substance of the pyrenoid, whereas no such invaginations have been observed in B. antillarum (Magne, 1976;Asensi et al, 1977). Second, in B. antillarum, the pyrenoid is terminal with respect to the direction of the thylakoids (Magne, 1976;Asensi et al, 1977;, whereas it protrudes laterally in A. ferruginea (Magne, 1976) and the Scytothamnales sensu stricto (Dele´pine et al, 1976). In summary, these observations suggest that two evolutionary events occurred on the common branch to A. ferruginea and the Scytothamnales: (1) the appearance of tubular invaginations of the plastid envelope in the pyrenoid, and (2) the migration of the pyrenoid from a terminal to a lateral position with respect to the thylakoids.…”

“…These include members of the Scytothamnales sensu Peters & Clayton (1998) (i.e. the three genera Scytothamnus, Splachnidium and Stereocladon), which have a focal chloroplast with stellate lobes and a central pyrenoid embedded in the stroma (Dele´pine & Asensi, 1975;Dele´pine et al, 1976;Asensi et al, 1977;Clayton, 1986;Peters & Clayton, 1998;Ouriques & Bouzon, 2000;Tanaka et al, 2007). A superficially similar but structurally quite different arrangement is found in Asteronema (currently placed in the Scytothamnales but so far not assigned to a family), Asterocladon (not included in an order despite its seemingly close relationship to the Ectocarpales: Mu¨ller et al, 1998;Peters & Ramı´rez, 2001;Uwai et al, 2005) and Bachelotia (which has been proposed to be merged into the Scytothamnales; Silberfeld et al, 2010).…”

Marine benthic algae of Namibia

“…Moreover, Delépine et al (1976) held that the arrangement of plastids in a stellate manner in both genera indicates converging evolution because these taxa have little phylogenetic affinities. This opinion has been recently supported by molecular studies (Reviers and Rousseau, 1999;Rousseau et al, 2001).…”