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Stick insects synthesize their own bacterial enzymes

At some point, stick insects picked up the genetic code for pectinase synthesis.

By
Brooks Hays
The Vietnamese stick insect species Ramulus artemis is one of several that acquired bacterium genes enabling the synthesis of the digestive enzyme pectinase. Photo by Matan Shelomi/MPI Chem. Ecol.
The Vietnamese stick insect species Ramulus artemis is one of several that acquired bacterium genes enabling the synthesis of the digestive enzyme pectinase. Photo by Matan Shelomi/MPI Chem. Ecol.

JENA, Germany, May 31 (UPI) -- Microbes inside the guts of animals, including humans, produce enzymes that break down food. These enzymes team-up with those naturally produced by the body to aid digestion.

Not all beneficial microbes are easily acquired, however. That's a problem for insects that rely on a group of microbial enzymes called pectinases to break down plant cell walls.

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According to a new study scientists with the Max Planck Institute for Chemical Ecology, stick insects have side-stepped this dependency problem by learning to synthesize their own pectinase.

"Insects are not supposed to make their own pectinases," Matan Shelomi, a postdoctoral fellow with the Institute for Chemical Ecology's entomology department, said in a news release.

At some point, stick insects picked up the genetic code for pectinase synthesis from a common microbe -- most likely from gamma-proteobactera.

"We are not sure how it happened, but one or two pectinase genes from a gut bacterium or even just something in the food clearly jumped into the stick insect genome, and then evolved along with the insects," said Shelomi.

Not all stick insects produce pectinases. A short stick insect species in California called Timema cristinae does not, while the latest study suggests all species belonging to the group known as "Euphasmatodea" do. To trace the origins of the gene jump, researchers compared genomes of several species with a database containing the genomes of more than 1000 insect species.

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The analysis suggests Euphasmatodea insects picked up the special genes just after the divergence of Timema cristinae, between 110 to 60 million years ago, but before the lineage diversified into the 3,000 species it features today.

The acquisition of special enzyme genes may have enabled the evolutionary success and remarkable diversity of the stick insect.

"Something happened, to make the tiny Timema become a planet-wide group of nearly 3,000 species that can be nearly half a meter long," concluded Shelomi.

The latest research was published this week in the journal Scientific Reports.

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