Tremendous Transfer – Intracellular and Horizontal Gene Transfer in the Genome of the Basal Angiosperm Amborella trichopoda

Amborella trichopoda, most likely sister to all other extant angiosperms, is the only “basal angiosperm” that has sequenced nuclear and organellar genomes. The Amborella mitochondrial genome is extremely unusual owing to its record-setting content of foreign DNA (Rice et al. 2013). The origins of the foreign DNA are the Amborella plastid genome and mitochondrial genomes of other angiosperms, mosses, and green algae, acquired via both intracellular and horizontal gene transfer. The phylogenetic diversity of the foreign DNA derives from epiphytic plants that grow all over Amborella. The ability to produce new shoots from wounded branches may also have contributed to the high degree of horizontal gene transfer. Intracellular gene transfer, on the other hand, is common in plants, especially in the mitochondrial and nuclear genomes. Given the unique mitochondrial genome, the nuclear genome of Amborella could be a potent recipient of organellar and foreign DNA. Here we address: 1) whether the nuclear genome also shows evidence of extreme levels of HGT and IGT (intracellular transfer between compartments of the cell), 2) how patterns of IGT and HGT are being used to understand when and how these massive transfers may have occurred, and 3) the kinds of analyses that are most effective at detecting and understanding these processes in Amborella and other plants.