Rafflesia cantleyi, perhaps better known as the corpse flower for its pungent scent, steals everything from its host. Though each blossom can be in excess of three feet across, the massive buds cannot support themselves, and have no leaves, stalks or true roots. Instead, they rely entirely upon their vine host,Tetrastigma rafflesiae, for survival. Harvard researchers have now discovered that food and water aren’t the only things the corpse flowers steal – over the course of evolutionary history, Rafflesia has also stolen Tetrastigma‘s genes.
The corpse flower and its host have a very intimate relationship. From the start, Rafflesia burrows into the Tetrastigma‘s tissues, growing as thread-like strands in direct contact with the surrounding vine’s cells. They are so dependant on their host that the corpse flowers have even lost the ability to make chlorophyll, a requirement for photosynthesis, and thus defy the very nature of being a plant by being unable to produce food from sunlight. These parasites feed off their host vines, growing and growing until they finally erupt, dramatically if briefly, into large, rubbery flowers that stinks like rotting flesh.
Somehow, after generations and generations of intimate contact between parasite and host, Rafflesia has ended up with more than the usual parasitic spoils. As a new study published today in BMC Biology reveals, the parasite expresses dozens of genes that it has co-opted from its host.
The passage of genes from distant lineages, such as the corpse flower and its vine host, is known as horizontal gene transfer. Though common in bacteria (e.g. the transfer of antibiotic resistance), it is much rarer in plants and animals, and we still don’t fully understood how it occurs.