Multiple acetylcholinesterases in Pardosa pseudoannulata brain worked collaboratively to provide protection from organophosphorus insecticides

Acetylcholinesterase (AChE) is an essential neurotransmitter hydrolase in nervous systems of animals and its number varies among species. So far, five AChEs have been identified in the natural enemy Pardosa pseu-doannulata. Here we found that Ppace1, Ppace2 and Ppace5 were highly expressed in the spider brain, among which the mRNA level of Ppace5, but not Ppace1 and Ppace2, could be up-regulated by organophosphorus in-secticides at their sublethal concentrations. In spider brain, the treatment by organophosphorus insecticides at the sublethal concentrations could increase total AChE activity, although high concentrations inhibited the ac-tivity. The activity that increased from the sublethal concentration pretreatment could compensate for the ac-tivity inhibition due to subsequent application of organophosphorus insecticides at lethal concentrations, and consequently reduce the mortality of spiders. PpAChE1 and PpAChE2 were highly sensitive to organophosphorus insecticides, and their activities would be strongly inhibited by the insecticides. In contrast, PpAChE5 displayed relative insensitivity towards organophosphorus insecticides, but with the highest catalytic efficiency for ACh. That meant the up-regulation of Ppace5 under insecticide exposure was important for maintaining AChE activity in spider brain, when PpAChE1 and PpAChE2 were inhibited by organophosphorus insecticides. The study demonstrated that multiple AChEs in the spider brain worked collaboratively, with part members for maintaining AChE activity and other members responding to organophosphorus inhibition, to provide protection from organophosphorus insecticides. In fields, high concentration insecticides are often applied when ineffective controls of insect pests occur due to relative-low concentration of insecticides in last round application. This application pattern of organophosphorus insecticides provides more chances for P. pseudoannulata to survive and controlling insect pests as a natural enemy.

Automated summary

This study found that the use of organophosphorus insecticides in spiders can inhibit the activity of acetylcholinesterase (AChE). However, treatment with sublethal concentrations of these insecticides can actually increase total AChE activity in spider brains, thereby reducing spider mortality. Specifically, the up-regulation of Ppace5 is important for maintaining AChE activity when other AChEs are inhibited.