Parasites are seldom popular, but the creepy behavior of certain parasitic plants would make them really hated, if only their victims were capable of emotion. These plants don’t just steal the nutrients others have worked so hard to acquire, they have grabbed more than 100 genes from plant species they were preying on, increasing their effectiveness as exploiters.
Non-biologists may think the ability to produce carbohydrates to store chemical energy through photosynthesis is the essential feature of being a plant. However, while the vast majority of the plants are doing the hard work of turning the Sun’s energy into something useful for themselves and the rest of the ecosystem, a few species have become the botanical equivalent of vampires. Using features called haustoria they suck the lifeblood, in the form of water and nutrients, from the plants they latch onto.
Dodder is one of these parasites. Although some plant parasites specialize in preying on a single genus or even species of plant, dodder is a generalist.
Professor Claude dePamphilis of Penn State University examined the dodder genome and was surprised to discover how many genes it had acquired through a process known as horizontal gene transfer.
"Horizontal gene transfer, the movement of genetic material from one organism into the genome of another species, is very common in microbes and is a major way that bacteria can acquire antibiotic resistance," dePamphilis said in a statement. "We don't see many examples of horizontal gene transfer in complex organisms like plants, and when we do see it, the transferred genetic material isn't generally used. In this study, we present the most dramatic case known of functional horizontal gene transfer ever found in complex organisms."
In Nature, dePamphilis reports on 108 genes some or all dodder species appear to have acquired through horizontal gene transfer and are now using to perform a wide variety of plant functions. These include defenses against other attackers and even the structure of the haustoria, the very instruments used to tap into the prey.
Most insulting of all is a gene that produces small RNA segments that are injected into the host plant to silence its anti-parasite defenses. This gene too was “stolen” through horizontal transfer.
Eighteen of the genes occur in every species of dodder dePamphilis studied, indicating they were acquired by the doddering ancestor and have been useful enough to be preserved ever since. Indeed, dePamphilis thinks their acquisition may account for a lot of dodder’s success as a parasite.
One thing dePamphilis doesn’t know and is keen to explore is whether any genes go the other way, and if so whether the plants dodder preys on get some compensation for all the nutrients they lose, or just acquire useless DNA sequences.
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