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Carnivorous Plant Evolution

CU School of Medicine

2/6/2017

AURORA, Colo. – A team of scientists that includes researchers from the University of Colorado Anschutz Medical Campus have sequenced the genome of the Australian pitcher plant and discovered a key to the mystery of how those plants became predatory. 

Australian pitcher plants evolved to include carnivorous pitcher leaves and non-carnivorous flat leaves and that feature allowed the scientists to analyze the genetic basis for carnivory by comparing the two types of leaves.

The findings are reported in an article in the Feb. 6 issue of the journal Nature Ecology and Evolution. 

Lead author Kenji Fukushima, PhD, began the pitcher plant genome project while a graduate student under the guidance of co-author Mitsuyasu Hasebe, Professor at the Graduate University for Advanced Studies (SOKENDAI) and National Institute for Basic Biology (NIBB) in Japan. Fukushima is a postdoctoral research fellow of the Japan Society for the Promotion of Science at the University of Colorado School of Medicine, conducting research in the laboratory of David Pollock, PhD, professor of biochemistry and molecular genetics.

The team of scientists sequenced and analyzed the nuclear genome of the Australian pitcher plant, which drowns its prey in an inescapable vat of digestive juices. The team found changes in its genome that were linked to remarkable characteristics of carnivorous plants such as prey attraction, trapping, digestion and nutrient absorption. 

Pitchers, or pitfall traps, are also a classic example of convergent evolution, a phenomenon that occurs when distantly related organisms end up with similar forms and function in response to similar environmental challenges. Their convergent biology explains why the original proponent of natural selection, Charles Darwin, shared Dr. Fukushima’s fascination with carnivorous plants. 

The scientists analyzed pitcher plant digestive fluid, an enzyme cocktail secreted from their specialized leaves, in three independently evolved pitcher plants and a sticky carnivorous plant Drosera. The study concluded that in addition to convergent digestive physiology, the separately arisen digestive enzymes often incorporated similar genetic components, even though the lineages had split more than 100 million years ago, long before their respective carnivorous habits arose. 

“It turns out that carnivorous plants are an amazing story of convergent evolution in systems at multiple scales. The physiological convergence of leaf form and function is associated with convergent evolution in enzyme repertoires, gene expression patterns, and most strikingly, amino acid substitutions. Excess convergence is strong evidence of natural selection, especially when found on multiple scales,” said Pollock, who is a coauthor of the article along with graduate Structural Biology and Biochemistry PhD student Stephen Pollard. 

The research team also included groups led by Victor Albert (University at Buffalo) and Shuaicheng Li (BGI-Shenzhen and the University of Hong Kong in China).

A full list of authors is available online. The title of the paper is “Genome of the pitcher plant Cephalotus reveals genetic changes associated with carnivory.”