Rnai Of Ace1and Ace2in Silkworm And Rice Stem Borer Reveals Their Differential Function

Acetylcholinesterase (AChE, EC3.1.1.7) is the key enzyme in insect nervous system.Its classical function is to hydrolyze the Ach, the transmitter of chemical information, by which nervous synapse transmits, into acetic acid and choline, preventing nervous transmission from depolarization disconnecting caused by over excitation. AChE is the target of organophosphorus and carbamates pesticides. But it has recently been found that AChE has many non-classical functions including embryo lethality, action incoordination, cell adhesion, synapse genesis.It has been found that multiple AChE genes exist in Diptera,Homopterous and Lepidop terous insects.Multiple AChE genes appeared before the differentiation of arthropods. However, there is only one AChE gene, ace2, in Drosophila, posssibly due to a second lose event in the evolutionary process. It is generally believed that AChEl is the main target of pesticides in many insects. In this study, the expression of two AChE genes in stripped rice borer and silkworm was interfered by RNAi and their functions were investigated.The major results are as follows:1) FAM labeled siRNA was injected into the bodies of silkworm and rice stem borers. The results showed that FAM-labeled siRNAs can pass through brain-blood barrier (BBB). The expression of AChE genes were knockdown sucessfully.2) We knockdown Bm-Ace and Cs-Ace respectively. The mRNA abundance in different tissues before or after RNAi treatment was estimated using qRT-PCR. The results showed that the expression of Bm-ace2was significantly higher than that of Bm-acel. However, the mRNA abundance of Cs-ace1was significantly higher than that of Cs-ace2. The Ace genes in the treated insects had reduced most in the head and muscle.3) The results showed that the mRNA abundance of two Ace genes in the third instar of silkworm had reduced at72h after siRNA injection, The AChE activities were reduced by25%at96h after siRNA injection.Interfering of Bm-ace2but not Bm-acel led to high reduction of AChE activity, indicating that Bm-AChE2is the major enzyme in silkworm.The feeding capacity of both si-ace1and si-ace2treated insects was significantly affected at5-days after injection. The weights and lengths were significantly reduced at14day after injection. The pupa malformation of si-ace treated insects were observed at21d after injection, proving that AChE plays an important role in the growth and development in insects.