Phragmoplastin, green algae and the evolution of cytokinesis

Phragmoplast-mediated cell division characterizes the land plants in the streptophyte lineage and some species of the green algal orders Coleochaetales, Charales and Zygnematales that are basal to that lineage. This type of cell division is generally not found in the other green plant lineage, the chlorophyte algae. A well-developed phragmoplast-type cell division has been documented, however, in two subaerial green algae (Cephaleuros parasiticus and Trentepohlia odorata) belonging to the order Trentepohliales--an order that molecular sequence data place unequivocally within the chlorophytes rather than streptophytes. Is the phragmoplast-mediated cell division of the Trentepohliales a case of homology or non-homology? To gain more insight into this question, we are exploring the potential phylogenetic information inferred from gene sequences of phragmoplastin, a dynamin-like protein that has been associated with cell-plate formation during phragmoplast-mediated cytokinesis in land plants. Primers for green algae were designed based on an available phragmoplastin sequence from soybean and yielded PCR amplifications from the trentepohlialean green algae Trentepohlia and Cephaleuros and the leafy liverwort Bazzania: These are the first published data for phragmoplastins in algae and liverworts. Analysis of phragmoplastin gene sequences in chlorophyte and streptophyte green algae may help to chart the evolution of the development of the phragmoplast.