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Plants, animals more closely linked, ECU biologist finds

GREENVILLE, NC   (Oct. 19, 2007)   —   It’s not just that John Stiller wants people to know that plants and animals are more genetically linked than they had believed to be in the past.

Stiller, a professor of biology at East Carolina University, wants his findings to illustrate the larger concern he has about the methods biologists are using to track and classify genetic material and the trees that order and organize them.

“Plants and animals share molecular, biochemical, and genomic-level features that suggest a relatively close relationship between the two groups,” Stiller said.

Stiller’s findings appear in the August 2007 issue of the journal, “Trends in Plant Science.”

The most common methods that compare only DNA sequences, Stiller believes, tend to obscure a “relatively close evolutionary relationship between plants and animals.”

Creating a genomic analysis from a set of cells (multicellular eukaryotes) that had a function “known” to Stiller and his research associates, Stiller found in his analysis at least five key areas in which the function of plant cells and animal cells were far more similar than those of fungi. It has been a long-held belief that fungi and animals are more closely related; Stiller’s study now suggests that plants are closer to animals than previously thought.

"In both green plants and animals, cell cycles are controlled by master switches," he said. "These function, and malfunction, similarly in both groups."

Other similarities in plants and animals include: overall content of protein families and domains; cancerous cells that divide rapidly if left unchecked; pathways for sensing external stimuli; and unique enzymes that process RNA so that it functions properly.

The links Stiller highlights between the plant and animal kingdoms are contained in genetic material that many biologists concerned with classification have long disregarded as anomalies in the data. But, said Stiller, it was in these anomalies that he discovered the similarities among the plant and animal kingdoms.

Stiller says he doesn’t have a problem with naming and ordering the biological world; he sees it as a most useful tool for education and research; but he does believe that the system used to classify it must be both as accurate and precise as possible, even if the sequencing takes and poses conflicts in the data.

“What is so powerful and appealing about these trees is they absolutely get a clear answer,” Stiller said. “Naming groups is a powerful tool; it goes back to Aristotle and Linnaeus. People always have been very concerned with how nature is ordered.”

Stiller is hopeful that his findings will encourage those who develop the trees of life using DNA sequencing methods to not disregard the conflicts, and rather embrace them to get the most accurate picture of the natural world.

“I think we should suspend belief in the dogma of the tree and look where these [organisms] really fit in, to see if there is a unifying message,” he said. “I’m in favor of a global signal. Let us emphasize the conflicts in the data, not ignore them. They may be telling us more than we think.”


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