Aedes Albopictus Diapause And Its Photoperiodic Regulation Mechanism

Background:Aedes albopictus is among the 100 most invasive species worldwide and poses a major risk to public health.Photoperiodic diapause provides a crucial ecological basis for the adaptation of this species to adverse environments.Ae.albopictus is the sole vector transmitting dengue virus in Guangzhou,but its diapause activities herein remain obscure.Diapause in Ae.albopictus appears in the egg stage,and the maternal photoperiodic effect determines whether the female mosquitoes produce the diapause eggs.However,the mechanism of photoperiodic regulation is still unclear,which is different from the interpretation of circadian rhythm.Therefore,this study systematically studies the characteristics of diapause behavior and the mechanism of photoperiodic regulation in the wild populations of Ae.albopictus in Guangzhou.Methods:The field investigations,diapause induction,determination and the critical photoperiod(CPP)observation in the laboratory,combined with the statistical analyses using a distributed lag non-linear model(DLNM)and a four-parameter logistic(4PL)regression model,were utilized for characterization of diapause behavior in the wild populations of Ae.albopictus in Guangzhou.Two wild strains from Guangzhou and Haikou were disposed under LD/SD(long/short photoperiod)conditions,and the female mosquitoes' heads were sampled at two time points of ZT4(light)and ZT20(dark),respectively,after individual diapause determination.The molecular mechanisms of diapause photoperiodic regulation in Ae.albopictus were demonstrated by Multi-omics analyses including RNA-de novo and small RNAomics.Results:Diapause behavior in the wild population of Ae.albopictus in Guangzhou was confirmed,CPP was 12.312 h,and the diapause incidence was significantly negatively correlated with photoperiod.Diapause incidences show a significant seasonal dynamics.The diapause eggs appeared around September in each year,and the diapause incidence decreased to zero in early March in the following year,while a lot of diapause eggs turned to develop to larvae after diapause termination.The diapause egg of Ae.albopictus is the main stage for overwinter in Guangzhou.107632 high quality all-unigene were gained by RNA-de novo,of which 62,801(58.35%)were annotated.In SD groups of Guangzhou wild strain,there were 98 DEGs(differentially expressed genes)in the light period,while 118 DEGs in the dark period,3 DEGs in the light and dark periods,and 244 DEGs in the unique light-dark period oscillation.Among them:the circadian clock genes per,cry2,vriand pdf are important DEGs,per and vri were found with different isoforms,which respectively expressed in the light and/or dark periods in SD groups.Taken away the molecular background in the control groups of Haikou strain,the differentially expressed miRNAs and piRNAs in SD groups of Guangzhou strain,only appeared in the light phase were 52 and 22,in the light and dark periods were 36 and 11,only in the dark period were 53 and 52,unique in the light-dark period oscillations were 22 and 20,respectively.Among them:miR-34 and miR-124 was only differentially expressed in the light stage,while let-7 and miR-8 in the light and dark periods,bantam and miR-278 in the dark period in SD groups of Guangzhou wild strain.Conclusions:Diapause behavior of Ae.albopictus in Guangzhou was confirmed and comprehensively characterized.Diapause in Ae.albopictus is significantly related with photoperiod,with seasonal dynamics.Therefore,for the efficient prevention and control of mosquito-borne diseases,citywide public health campaigns in Guangzhou should start in early March.Furthermore,this study also provides an optimized investigation system and statistical models for the study of Ae.albopictus diapause.The differentially expressed molecules including DEGs,miRNAs and piRNAs were 463,163 and 105,respectively.Among them,per,cry2,vri and pdf were the important DEGs,which might involve in the diapause photoperiodic regulation,but different from the circadian regulation pathway.This study will benefit for further clarification of the photoperiodic regulatory pathway in Ae.albopictus diapause,and provide scientific data for exploring a new way to control the mosquito population by blocking the diapause process during the maternal stage in Ae.albopictus,as well facilitating the study on photoperiodic diapause and regulation pathway for photoperiodic calendar in other insects or organisms.