Physiological and biochemical studies on negatively correlated cross resistance in the green rice leafhopper

据认为，稻纵卷叶蝉对N-甲基氨基甲酸酯和有机磷的抗性主要原因是乙酰胆碱酯酶(AChE)对这些杀虫剂的敏感性降低。本研究建立了一种通过测定昆虫个体对杀虫剂的AChE敏感性来监测抗性的简易生化监测方法。该方法可用于监测稻纵卷叶蝉对N-甲基氨基甲酸酯和有机磷的抗性。利用这种监测方法，我们发现N-氨基甲酸甲酯和久效磷(OP)的组合在体外AChE抑制下对稻纵卷叶蝉的交叉抗性表现出负相关。然而，生物测定没有发现这种独特的关系。因此，将野生型菌株的N-甲基氨基甲酸酯抗性基因导入敏感品系，选育出RMC品系。利用敏感品系和RMC品系，我们发现两种杀虫剂之间存在负相关的交叉抗性。通过生物测定未能在田间品系中发现负相关的交叉抗性，其原因是在抗性品系中分离久效磷的脂肪酸酯酶(ALIE)增加。通过不同菌株的配对交配，我们发现GRLH具有6种AChE同工酶。我们可以净化AChE约3000倍。这两种酸痛在生化特征上有明显的差异。我们将阐明AChE抑制中负相关交叉耐药的分子机制。

It is acknowledged that the major cause of N-methyl carbamates and organophosphates resistance in the green rice leafhopper, Nephotettix cincticeps Uhler, is a reduced sensitivity of acetylcholinesterase(AChE) to these insecticides. In this study, a simple biochemical monitoring method for resistance by assaying sensitivity of AChE of individual insects to insecticides was established. And this method was found to be useful for the monitoring of N-methyl carbamamates and organophosphates resistance in the green rice leafhopper. By using this monitoring method, we found that the combination of N-methyl carbamate and monocrotophos (OP) showed negatively correlated cross resistance in the green rice leafhopper at in vitro AChE inhibition. However, this unique relation was not found by the bioassay. Thus, N-methyl carbamate resistance gene of the field strain was introduced to a susceptlble strain, and we bred Rmc strain. Using a susceptible and Rmc strains, we found that there is a negatively correlated cross resistance between the two insecticides. The cause we could not find the negatively correlated cross resistance in the field strain by bioassay was found to be an increased aliesterase(AliE) which sequestered monocrotophos in resistant strain. By pair mating of various strains, we found that the GRLH possess 6 isozymes of AChE.We tried to isolate and purify AChE of heads from a susceptible and resistant strains. We could purify AChE about 3000 times. There was a clear difference between these two AChEs in biochemical characters. We are going to clarify molecular mechanism of negatively correlated cross resistance at AChE inhibition.