Divide and rule

日期:2017-06-05 01:50:49 作者:农忾怿 阅读:

By Bob Holmes in Santa Cruz LAND plants may owe their evolutionary success to the accidental duplication of a gene early in their history, say scientists in the US and Germany. The gene in question codes for actin, a key component of the internal skeleton of cells. Like animals, higher land plants have many different actin genes, and the different versions of the protein have different properties. This diversity helps cells perform specialised functions, an essential step in the evolution of complex multicellular organisms. For years, however, researchers have debated whether the variety of actin genes was what enabled land plants to diversify, or whether the genes diversified later. Now researchers believe they have evidence to support the first theory. Debashish Bhattacharya of the University of Iowa in Iowa City and his colleagues sequenced the actin genes of three primitive land plants, and several green algae. The green algae have a single version of the gene, they found, as does Mesostigma viride, a single-celled organism that represents the lowest branch on the evolutionary tree leading to land plants. In contrast, all the other primitive land plants they studied have at least two actin genes—evidence that the gene was duplicated around the time the lineage evolved. Higher up the tree, more duplications appear, Bhattacharya told a meeting of the International Society for Evolutionary Protistology in Flagstaff, Arizona, earlier this month. This suggests that gene duplication and divergence were key events in the origin of complexity in land plants, he says. The evidence fits well with other data, says Richard Meagher, an expert on the actins of higher plants at the University of Georgia. But to clinch the point, he says,