Where have all the plants come from?

For many years it has been the considered view that land plants had evolved some 500 million years ago from stonewort-like algae, something like the extant genus Chara. In a timely re-evaluation of this notion, Sabina Wodniok et al. (BMC Evolutionary Biology 11: 104; doi:10.1186/1471-2148-11-104) have examined a large phylogenetic data set of nuclear-encoded genes from 40 green plant taxa (Viridiplantae). Their conclusion is that either the Zygnematales – or a clade consisting of the Zygnematales and the Coleochaetales – are the sister group to the embryophytes (‘land plants’). Although this suggestion concurs with a previously published phylogenetic study of chloroplast genomes, the team concede that additional data are needed to confirm their conclusion. So, is this announcement of purely ‘academic’ interest? It is certainly an academic study, but trying to identify the ancestors of our land flora is important in directing studies on the course of that evolution to the correct organisms. Nevertheless – and until this idea is overturned – class study of Spirogyra will take on an even more important dimension if it is viewed as a potential land-plant ancestor! I’m sure the students will be suitably impressed, providing they’ve set up their microscopes properly.