Reversing Insecticide Resistance Using CRISPR

 

Researchers have tested using CRISPR to reduce insecticide resistance in pests. In simple form, this was done by editing the gene which controls insecticide resistance by returning it to a wild type allele, making it susceptible to insecticides. This obviously came with ethical concern so the researchers only made it a temporary solution. Hence, why they returned the gene to wildtype rather than removing the insecticide-resistant variant genes entirely by replacing them with susceptibility to pesticide genes. They term for this is a e-Drive cassette which spreads through CRISPR gene editing which binds to Cas9 DNA and cuts out voltage gated sodium ion channel (vgsc) insecticide resistant gene site. This solution is not permanent since removing insecticide resistance lowers fitness of pests.

What the e-Drive essentially does is disable the insecticide resistance gene by using CRISPR to ensure that the wild-type gene has a 100% frequency of being passed to offspring. Since the non-resistance gene is being spread rapidly, it can spread faster than the resistance gene within just a few generations, 8 to 10 to be specific. Although the cassette was also inserted with a fitness check which limits viability or fertility. So the wild type gene spreads, increasing susceptibility and reducing pests (for example on crops), then over time the added fitness check along with the natural lower fitness takes over and the non-resistant pests eventually die out. The population returns to a normal resistant one. The beauty of this e-Drive cassette is that it can be reintroduced whenever needed, for example, if the pest problems become large again, then the e-Drive can easily be added back. It is a short term, effective, easily implemented, and easily removed strategy that the researchers hope could also work on mosquitos for malaria.

This is a great development because insecticide-resistance is rapidly spreading throughout populations of pests. While we need to control pests from destroying things like crops, it is becoming increasingly difficult to use pesticides to kill them. We also do not want the e-Drive to become out of control which could seriously harm pest populations. As the researcher says, this strategy will work without creating any other perturbation to the environment. If we can successfully increase pesticide effectiveness without entirely harming a pest population, I am all for it.

Links

https://www.sciencedaily.com/releases/2024/11/241122172740.htm

https://www.epa.gov/pesticide-registration/slowing-and-combating-pest-resistance-pesticides

Pesticide Runoff is affecting Aquatic Mammals due to Lost Genes

Today’s Marine mammals have all evolved from terrestrial mammals that trekked back into aquatic environments and created adaptations to thrive in these new environments. One of the genes they lost in adapting to aquatic life was an enzyme that would aid in defending against pesticides. With this discovery of a missing gene in marine mammals make the issues of pesticide runoff in oceans an even more important issue in our environment. The gene responsible for this defense was labeled as PON1 which was identified to defend against organophosphates, the pesticides used in agriculture. Most marine mammals have pieced together similar enzymes to replicate the results of the PON1 gene with some exceptions being walruses, fur seals, and spotted seals, all of which would be the most vulnerable to organophosphates. Now why did these marine mammals adapt to lose this gene that their terrestrial ancestors once had? The leading theory is that due to the fact that marine mammals take in large amounts of oxygen for deep dives, they evolved to remove oxygen carrying molecules. Molecules such as PON1, that otherwise would be harmful under the pressure of deep dives. (Zimmer, 2018)

These pesticide runoffs have also started to affect coastal avian species as well as the marine mammals. There have been a rise of unidentified diseases and conditions related to issues with the organisms endocrine systems. With an organisms endocrine system being exposed to its surroundings, many believe that these pesticide runoffs are to blame for the unusual mutations and reactions of these organisms. (Tanabe, 2009)

Even though there isn't evidence that directly links the runoff to these mutations and diseases in coastal organisms such as mammals and avians, the consensus of these researchers are that the pesticides have a part to play in this ecological issue. It is impossible to know exactly where runoff from agriculture will wind up but it is a guarantee that it will reach the oceans at once point. This means that we have to be conscious of the volume of pesticides we use on our plants as well as the possible reactions that organisms in the oceans and waterways will have to these chemicals. Although there aren’t direct links to the issues marine mammals are facing, i suspect that in the coming years more information will be discovered on the effects of such pesticides on marine mammals and other ocean going species.

References

Tanabe, S. (2002, 09). Contamination and toxic effects of persistent endocrine disruptors in marine mammals and birds. Marine Pollution Bulletin, 45(1-12), 69-77. doi:10.1016/s0025-326x(02)00175-3

Zimmer, C. (2018, August 09). Marine Mammals Have Lost a Gene That Now They May Desperately Need. Retrieved from https://www.nytimes.com/2018/08/09/science/marine-mammals-pesticides.html

Caffeinated fruit flies help identify potential genes affecting insecticide resistance

A group of scientist at the university of Kansas devised a technique to be able to potentials locate and label the resistant gene found in many insecticide resistant insects. Caffeine was used as the primary locator of for the resistant gene. Because caffeine has a chemically similar structure to its surrogate, xenobiotics, it was employed to help the scientist track the location of the gene on Drosophila melanogaster.

The scientist doggedly test 1700 lines of fruit flies and their response to caffeine. they were able to determine 10 trait loci of genes containing either the resistance or susceptibility to caffeine and identified CYP12d1-d CYP12d1-p as the culprits responsible for being the enabling enzymes that detoxify toxic compounds. These genes come from a family of P450 compounds. The scientists subsequently found that those two gens alone, make up for 10 percent of the fruit flies variation in resistance to caffeine. This approach can hopefully be employed to identify many genes that are associated with resistance to any drug.

This new information can help increase the economic yield for crop and at the same time make it cheaper for people to buy certain plants. Farmers will be able to produce more crop that are resistant to insects and other pest. Also the ability to locate genes is becoming more clearer with experiments like these.

Main Article: http://www.sciencedaily.com/releases/2014/03/140327101417.htm

Related Article: http://abstracts.genetics-gsa.org/cgi-bin/dros14s/showdetail.pl?absno=14531586

Caffeine Used On Fruit Flies to Investigate Insecticide Resistance Genes

Insect crop pests have been gradually developing resistance to chemical pesticides for more than fifty years. The genes of fruit flies (Drosophilia melangaster) were analyzed by scientists at the University of Kansas to determine the loci in which these resistance traits reside. They used caffeine as a chemical substitute for a pesticide, a common practice in analyzing xenobiotics.


The response or resistance to caffeine was tested in 1,700 flies, and they were able to map ten trait loci. In one of the stretches of DNA mapped they identified two genes that code for enzymes involved with unarming toxic compounds: Cyp12d1-d and Cyp12d1-p, members of the cytochrome P450 gene family. These two genes contribute over 10 percent of the variation of fruit flies' resistance to caffeine.
It is important to understand the nature of insect's resistance to pesticides because their inheritable ability to overcome chemicals causes all kinds of issues: It increases our need to strengthen chemical pesticides, which we inevitably ingest. Further, the climbing strength of these pesticides have environmental effects on the local soil and fauna/flora. And the most obvious, it can be detrimental to crop yield, which affects food prices and availability.


Article:  http://www.sciencedaily.com/releases/2014/03/140327101417.htm
Related Article (more info on insecticide resistance): http://abacus.gene.ucl.ac.uk/jim/pap/mallet89tree.pdf

Got the travel bug? There's a good chance you do

If you like to travel, like I do, you'll be disturbed to hear it's getting harder to kill the vacationer's No. 1 enemy: bedbugs.

[caption id="attachment_7227" align="alignright" width="337" caption="Thanks to their genetics, some bedbugs are immune to pesticides."][/caption]

A new study out this week in the journal Scientific Reports finds that certain colonies of bedbugs can turn on genes in their outer shells that help them shrug off the effects of pesticides. Scientists from the University of Kentucky in Lexington studied 21 groups of bedbugs and found that these genes "detoxify" pesticides and stop them before they get into the bedbugs' nerve cells. In addition, researchers found that the bugs also have a pesticide-resistant gene in their actual nerve cells, called kdr. This kdr gene plus the genes in their outer shells mean these bugs have two defense mechanisms to fight our bug sprays.

Knowing the shell is helping bedbugs survive pesticides "implies that better formulations can be designed to penetrate the cuticle (the protective outer shell layer) more effectively and thus provide better control," says entomologist Changlu Wang from Rutgers University in New Jersey.

However, scientists are still scratching their heads, wondering when these bedbugs developed their resistance qualities.

"Was it in the past ten years? The past 50? Or are we looking at the past several hundred years or more?" Zachary Adelman, an entomologist from Virginia Tech, says in a recent article of National Geographic.

Adelman says discovering the answer to that question could help scientists figure out how quickly bedbugs are evolving and what we can do to control their populations.

My wife and I travel often and this is always a concern for both of us but, especially for her. It's sad news for travelers to hear that these pests are becoming more resistant to pesticides. If you do happen to bring them home they will take over very quickly which can cost a small fortune to rid yourself of the problem. Maybe it's better to just stay home. However, a friend once told a story of how they knew a couple that had an infestation of bed bugs that spread throughout their home from a picture frame they purchased at a yard sale. So, there is more than just one way to catch a bug.