While all of the worms studied had the lin-48 gene, C. elegans was the only species to express the gene in its excretory cells. The researchers looked at the excretory cells because that's where they could easily see the differences in lin-48 expression.
In laboratory petri dishes, the worms were exposed to high levels of sodium chloride regular table salt.
The expression of lin-48 in the excretory cells appeared to give C. elegans a survival advantage over its relatives, as the other species were unable to process the excess salt, and more than three-quarters died as a result.
"Having lin-48 in the excretory cell changes the cell, but we're not sure how," Chamberlin said. "Lin-48 itself is a transcription factor it turns on other genes that theoretically help C. elegans handle excessive levels of salt. But we don't know what other genes it affects.
"Differences in gene expression contribute to structural and functional differences between species," she said. "In this case, C. elegans' excretory system can handle excessive levels of salt, which may give the worms an additional benefit of living in naturally salty environments where other worms can't survive."
The researchers concluded that C. elegans is more highly evolved than similar worm species because it developed a change in gene expression over time.
"This change made C. elegans more complex," Chamberlin said. "If we can understand how gene regulation becomes more complicated, it might tell us how organisms became increasingly complex."
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Contact: Helen Chamberlin
Chamberlin.27@osu.edu
614-688-0043
Ohio State University
18-Feb-2004