Miniview: Multiple origins of plasmodesmata

Abstract

Plasmodesmata in photosynthetic eukaryotes are found in all embryophytes, in many members of the Chlorophyta, and in the Phaeophyceae. The Phaeophyceae and the Chlorophyta clearly developed cell walls and multicellularity independently, so that (in the absence of lateral gene transfer) plasmodesmata evolved independently in these groups. The minimum number of independent origins of plasmodesmata in the Chlorophyta based on molecular phylogenies is two (Chlorophyceae sensu lato, Charophyceae sensu lato). Other intercellular connections in members of the Chlorophyta (Ctenocladus, Smithsoniella, Volvox) are structurally very different from true plasmodesmata. Recently published taxonomies of the Chlorophyta have five classes (Chlorophyceae, Oedegoniophyceae, Trentepohliophyceae, Klebsormidiophyceae and Charophyceae sensu stricto) with plasmodesmata out of a total of thirteen. However, it is by no means clear that these classes all acquired plasmodesmata independently.