The Expression Of Regulatory Genes Of Juvenile Hormone And Molting Hormone In Sex-dimorphic Development Of Phenacoccus Solenopsis

Phenacoccus solenopsis Tinsley,which has been recently found as an invasive exotic mealybug pest,has a great potential threat to economic crops.It is typically characterized by its extreme sexual dimorphism.The wingless female growth progresses through consecutive molts and maintain juvenile characteristics at the adult stage.In contrast,male,after two nymphal molts,enter two non-feeding quiescent stages,pre-pupa and pupa,in which the adult features are formed,such as developing wings.Insect metamorphosis is governed by two main growth hormones that act in concert: juvenile hormone(JH)and molting hormone(MH).There are differences in the variation of two hormones titers and related genes expressions under different type of metamorphosis.Despite the concomitant discovery of these two hormones,research on their molecular actions has mainly focused on holometabolous insects.There is still little study on hemimetabolous insects about two hormones,especially on scale insects.We firstly carried out experiments to find a set of the most suitable reference genes for both sexes of Phenacoccus solenopsis across all the different developmental stages,then the expression of several regulatory genes of JH and MH were measured in sex-dimorphic development of the pest.The main results were as follow:(1)Ten candidate genes were selected from P.solenopsis transcriptome data for this study.The amplification efficiency and melting curves of each candidate gene suggest that each of the primer pairs amplified a unique product.After analyzing the expression of ten candidate reference genes using common algorithms,we finally determined EF1-β and RP-L32 as the most suitable reference genes for the various developmental stages in male and female P.solenopsis.(2)JHAMT gene expression was high in the late second nymph stage for males;however,its expression decreased rapidly at the pre-pupa stage and nearly stopped at the pupa stage.Gene expression in males was higher than females at the pre-pupa stage among JHAMT,Kr-h1 and Gce.The results showed that JH levels are higher in males.Furthermore,male quiescent pupal-like stages were likely to be associated with higher transcript levels of JHAMT,Kr-h1 as well as Gce.(3)Gene expression pattern in males on USP was basically the same as normal molecular mechanism of ecdysone in other insects,however,showed the opposite trend in females.Broad(Br)and E93,the family of transcription factors,both showed extreme high levels at the pre-pupa stage in males.On the contrary,these two genes remained at low levels in females.In summary,there are significant differences in the expression of regulatory genes of juvenile hormone and molting hormone between females and males in P.solenopsis.The expression level of several key genes in the research in males is higher than that in females.Therefore,it is inferred that there is a certain link between these key genes and sexual dimorphism.This study helps to ensure the role of juvenile hormone molting hormone in sexual dimorphism of P.solenopsis,and to provide effective research and theoretical basis for scientific prevention and control of P.solenopsis.