Genetics: Orchid origin story illuminated by genome sequencing

The genome sequence of the orchid Apostasia shenzhenica is reported online in Nature this week. A. shenzhenica is a self-pollinating orchid species found in southeast China, and the findings provide new insights into the origins and evolution of the diverse and widespread orchid family.

Orchids represent about 10% of flowering plant species, encompass wide diversity in their morphology and lifestyle, and have successfully colonized almost every habitat on Earth. The Apostasia genus, along with one other genus, diverged early and forms a sister lineage to the rest of the orchid family. Zhong-Jian Liu, Yves Van de Peer and colleagues report the whole genome sequence of one of its members, A. shenzhenica. They also present transcriptome data (the set of RNA molecules that control the expression of an organism’s genes) for orchids from three other subfamilies, and new high-quality genome data for two species from a further subfamily.

The authors find that A. shenzhenica shows clear evidence of a whole-genome duplication, which is shared by all orchids and occurred shortly before their divergence. Comparisons with other orchids and flowering plants enable the authors to reconstruct an ancestral orchid ‘gene toolkit’, which sheds light on the genetic mechanisms that underlie key orchid innovations. These include the development of the labellum (a ‘lip’ on the flower that attracts insects) and the reproductive structure known as the gynostemium, as well as the evolution of epiphytism (the ability to grow on another plant).