Dual mutations in the whitefly nicotinic acetylcholine receptor ß1 subunit confer target-site resistance to multiple neonicotinoid insecticides.

Neonicotinoid insecticides, which target insect nicotinic acetylcholine receptors (nAChRs), have been widely and intensively used to control the whitefly, Bemisia tabaci, a highly damaging, globally distributed, crop pest. This has inevitably led to the emergence of populations with resistance to neonicotinoids. However, to date, there have been no reports of target-site resistance involving mutation of B. tabaci nAChR genes. Here we characterize the nAChR subunit gene family of B. tabaci and identify dual mutations (A58T&R79E) in one of these genes (BTß1) that confer resistance to multiple neonicotinoids. Transgenic D. melanogaster, where the native nAChR Dß1 was replaced with BTß1A58T&R79E, were significantly more resistant to neonicotinoids than flies where Dß1 were replaced with the wildtype BTß1 sequence, demonstrating the causal role of the mutations in resistance. The two mutations identified in this study replace two amino acids that are highly conserved in >200 insect species. Three-dimensional modelling suggests a molecular mechanism for this resistance, whereby A58T forms a hydrogen bond with the R79E side chain, which positions its negatively-charged carboxylate group to electrostatically repulse a neonicotinoid at the orthosteric site. Together these findings describe the first case of target-site resistance to neonicotinoids in B. tabaci and provide insight into the molecular determinants of neonicotinoid binding and selectivity.

An analysis on the reliability and validity of a scoring system of house -tree -person test for depression / 预防医学

Objective To develop a quantitative scoring system for the House -Tree -Person (H -T -P)test.Methods By literature review and expert consultation,preliminary evaluation items were defined.After pilot test,the scoring system for assessing depression were defined.A total of 21 6 cases of patients with depressive mood disorder from the Tong De hosptial of the Zhejiang Province were tested.The reliability and validity of a scoring system of house -tree -person test for depression were analyzed.Results The scoring system of depression evaluation including 23 items and 5 factors,could explain 77.50% of the cumulative total variance.The split -half reliability of the system was 0.87 and 0.88,and the internal consistency reliability of the system was 0.81 .The Kappa coefficient of each item was 0.71 -0.89 (P <0.01 ). The standard validity of the scale was 0.65,and the criterion validity of each factor was 0.34 -0.60 (P <0.01 ).The critical point of positive demarcation was 4,and the critical point of positive demarcation of each factor was 1 .The Kappa value of the consistency test was 0.85 with the PHI Depression Inventory.Conclusion This study demonstrates H -T -P scoring system has acceptable validity and internal consistency.