How the roundworms became resistant to avermectin
NEMATODES are one of the most difficult garden pests to control. These roundworms feed on plant roots and restrict the plant’s ability to absorb water and nutrients. They also cause various diseases in humans and animals. Usually, avermectin produced by Streptomyces avermitilis, a soil bacterium, is used as a pesticide and for treatment of nematodal diseases.
But nematodes have developed a resistance to avermectin, reasons for which are unknown. Now, scientists at Lewis-Sigler Institute for Integrative Genomics at Princeton University in the US have found why the resistance develops. They say a particular gene, known as GLC-1, is responsible. The resistance occurs due to deletion of the gene.
For their study the team compared laboratory-raised nematode Caenorhabditis elegans that had not developed avermectin resistance, to a resistant one captured from the Hawaiian islands. The researchers found that they could make the avermectin-resistant population drug-sensitive again by introducing the GLC-1 gene from the laboratory-raised nematodes. The scientists say avermectins affect certain regulatory channels on the nerve and muscle cells of C. elegans. The antibiotic binds to the neurotransmitter glutamate on the cell and closes the channels responsible for carrying out nerve impulses. This leads to paralysis of the nematode. In the resistant worms the binding site for glutamate is absent due to deletion of GLC-1 gene.
The team after comparison also noted that C. elegans raised in agricultural fields was more resistant than the one found in the forests. The reason for this they say is that nematodes in agricultural fields have spent at least part of their life in soil treated with avermectin in comparison to forests. The study was published in the February 3 issue of Science.
The researchers say the findings provide insights into genetic mechanisms by which organisms cope with environmental challenges and the possible evolution of drug resistance in pathogens. This could help devise better ways for their control.
We are a voice to you; you have been a support to us. Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.
.png)
Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.