RNA-seq Analyses Of Photoperiodic Diapause In Aedes Albopictus And Preliminary Identification Of Its Clock Gene Period

Background:Aedes albopictus has strong ability of biological invasion.Photoperiodic diapause is a plastic phenotype in Ae.albopictus,which lays a foundation for the critical ecological adaptation in unfavorable habitats.Diapause egg is the main overwinter stage in Ae.albopictus,which provides an important biological basis for its global spread and rapid transmission of mosquito-borne diseases such as dengue,Zika virus disease,etc.However,the molecular regulation mechanisms of photoperiodic diapause in Ae.albopictus is still not clear.Therefore,in the present study,the high thoughput RNA-seq was utilized for exploration of molecular regulation pathways of photoperiodic diapause in Ae.albopictus.Methods:Guangzhou wild strain(GZ strain sampling from the subtropical population with photoperiodic diapause in Guangzhou region)and Haikou wild strain(HK strain sampling from the tropical population without photoperiodic diapause in Haikou region)of Ae.albopictus were selected and disposed under long and short photoperiods(LD/SD)conditions.The females of Ae.albopictus were individually performed the induction and determination of diapause,and then the females’ heads were sampled at two time points of ZT4(light)and ZT20(dark),respectively.Therefore,a total of 8 groups was conducted with three repetitions per group,whilst 25-30 heads of female mosquitoes were collected in each sampling pool for further high throughput RNA-seq analyses.C6/36 genome reference-based assembly of Ae.albopictus was optimized,and the differentially expressed genes(DEGs)and differentially expressed transcripts(DETs)were further screened at the level of genes and transcripts.Moreover,the core clock gene period involved in DEGs/DETs in the biological clock regulation pathway was preliminarily identified.Results:A total of 116,892 transcripts and 38,416 unigene were obtained via analyses of the reference-based assembly of transcriptome.In comparison with the molecular background in the control groups of HK strain,GZ strain was observed with a higher number of transcripts.Whilst,DEGs and DETs specific in GZ strain that appeared only in the light phase were 289,and 678;in both light and dark periods were 11,and 47;only in the dark period were 297,and 1216;and unique,in the light-dark period oscillations were 193,and 617,respectively.Among them,the core clock gene per was one of the essential DEGs/DEFs,and observed differentially expressed in the level of transcripts.Our findings indicated that there was a complicated alternative splicing pattern in per gene,and at least five different isoforms of per gene have been identified.Conclusion:790 DEGs and 2358 DETs relative to molecular regulation of photoperiodic diapause in Ae.albopictus were identified via our in-depth RNA-seq study,in which per and other biological clock genes were involved in.The differential expression of per gene was mainly found at the transcriptional level,and five isoforms of per gene were preliminary identified.This study lays a foundation for further elucidating the photoperiodic regulation pathway of diapause in Ae.Albopictus.