Evidence for organelle origin

Genetic clues point to 'missing links' between hydrogenosomes and mitochondria

Charles Choi(cqchoi@nasw.org)
Mar 2, 2005

The first genetic evidence of hydrogenosomes—organelles found in some ciliates, trichomonads, and fungi that generate hydrogen and adenosine triphosphate (ATP)—that evolved from mitochondria is reported by Dutch and German researchers in Nature this week.

"Our findings prove the existence of missing links between mitochondria and hydrogenosomes," coauthor Johannes Hackstein of Radboud University Nijmegen in the Netherlands told The Scientist. "This has value in analyzing the evolution of the eukaryotic cell, to help better understand these organelles and possibly mitochondrial dysfunctions."

Hydrogenosomes resemble mitochondria morphologically, but generally lack a genome, hampering clarification of their origin. Considerable debate exists over whether hydrogenosomes evolved from aerobically functioning mitochondria that acquired an anaerobic metabolism or from endosymbionts capable of both aerobic and anaerobic function that mitochondria also descended from.

In 1998, Hackstein and colleagues found preliminary evidence that hydrogenosomes of the anaerobic ciliate Nyctotherus ovalis from cockroach guts might possess genes. In the...

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