MANHATTAN, Kan. – A Kansas State University researcher’s work has shed new light on which of two genes present in many insect species should be targeted for new insecticides that will be safer for humans and the environment than those currently used.
K-State entomology professor Kun Yan Zhu, along with a team of scientists at K-State, the Mayo Clinic, Oklahoma State University and China Agricultural University, uncovered the functions of two different acetylcholinesterase or AChE genes in the red flour beetle, which is a serious, globally-distributed insect pest of stored grains and grain products found in grain storage facilities, flour mills, grocery stores, warehouses and homes.
The research team’s findings were published Feb. 12, 2012 in PLoS ONE (www.plosone.com) and Feb. 27, 2012 in Scientific Reports (http://www.nature.com/srep/index.html), both are online scientific journals.
Acetylcholinesterase (AChE) is a crucial enzyme involved in cholinergic neurotransmission in the nervous system of insects and other animal species. The enzyme breaks down the neurotransmitter acetylcholine at the synaptic cleft (the space between two nerve cells) after acetylcholine has served the function of signal transmission. This keeps the synaptic cleft clear so that next signal transmission can occur.
Commonly used organophosphate insecticides, which are related to nerve agents, are known as anticholinesterases because they are potent inhibitors of AChE. Inhibition of AChE prevents the breakdown of acetylcholine by the enzyme. As such, acetylcholine continues to cause nerve signal transmission, which leads to overstimulation of the nervous system and eventual death of an animal.
For years, AChE was known to be encoded by a single gene in vertebrates and insects. But by 2002, in a breakthrough discovery, a team of researchers led by Zhu found a paralogous or second AChE gene in the greenbug, which is an aphid species that often causes serious damage to sorghum, wheat and other small grains in the world. Since Zhu group’s finding of a second AChE gene in the greenbug, scientists have quickly learned that many insect species have two different AChEs.
That earlier work, described in a scientific journal as “a breakthrough in this toxicological riddle…,” led to the latest work to determine which of the two genes studied in the red flour beetle is responsible for cholinergic neurotransmission. In turn, that tells the scientists which should be the target for anticholinesterase insecticides and is responsible for insecticide resistance conferred through the target gene mutations.