Genomic Clues to the Ancestral Flowering Plant

Amborella trichopoda is an understory shrub that is endemic to New Caledonia (see the figure). It is an early-diverging flowering plant—most phylogenetic studies indicate that it diverged from the lineage leading to most flowering plants, and it is the single sister species to all other extant angiosperms (1). As such, it represents the equivalent of the duck-billed platypus in mammals (in the earliest branch of the mammalian family tree). Given its pivotal position in flowering plant phylogeny, it has been of considerable interest to sequence its genome. On page 1467 of this issue, the Amborella Genome Project (2) reports the nuclear genome sequence, with extensive analyses. In addition, on page 1468, Rice et al. (3) report the complete sequence of the Amborella mitochondrial genome, which contains a massive amount of horizontally transferred DNA. And on page 1516, Chamala et al. (4) describe a new assembly and validation approach for the Amborella nuclear genome that can be applied to other nonmodel eukaroytes.