The Study On The Mechanism Of The Difference In The Number Of DC Bristles Between Drosophila Melanogaster And Musca Domestica

Both the Musca domestica and Drosophila melanogaster belong to the family of Diptera.In nearly 100 million years of evolution,they formed the externalized sensory organ bristles,which retained the common features of primitive ancestors and evolved their own unique phenotypes.Therefore,they are excellent genetic markers for studying the evolution of phenotypic traits.The development of bristles in drosocentral(DC)of D.melanogaster and M.domestica is different.M.domestica has six pairs of DC bristles,while D.melanogaster has two pairs of DC bristles,the specific mechanism of their difference in DC bristles is not clear yet.In this study,we took the Drosocentral(DC)bristles of the above two species as research subjects to study bristle developmental genes for elucidation of the reasons of the differences in the number of DC bristles between the two species in the evolutionary process and the regulatory mechanism of bristle development.The main results are as follows:1.The m RNA expression levels of genes scute(sc),emc,pannier(pnr),hairy and u-shaped(ush),which are related to the regulation of bristles development were analyzed,the results shows that there were significant differences in the expression levels of five genes between the two species.Therefore,we consider that the difference in these five genes expression may be one of the reasons for the difference in the number of DC bristles between the two species.2.Drosocentral Enhancer(DCE)element of D.melanogaster was replaced by the DCE regulatory element of M.domestica with CRISPR/Cas9 technology.The results showed that the number of DC bristles in transgenic flies increased.The results showed that the phenotypic differences of the DC bristles between species caused by the evolution of cis-regulatory sequences,which drove the differential expression of sc at the DC site.3.Electrophoretic mobility shift assay(EMSA)results showed that the cis-regulatory element upstream of emc gene,emc E6,can bind to the transcription factor PNR,which could regulate the expression of emc.Our results suggest that differences in expression levels of five genes may be one reason for the difference in the number of DC bristles between M.domestica and D.melanogaster.The evolution of cis-regulatory sequence DCE between species drives the differential expression of sc at the DC sites,which lead to the difference of the DC bristles phenotype.emc inhibits the development of bristles,and PNR protein is involved in transcriptional regulation by binding to the upstream cis-regulatory element of emc.Our research reveals the regulatory mechanism of phenotypic evolution and development at the molecular level,providing theoretical and experimental basis for evolutionary developmental biology.