Study On Sex-determining Network, And CDNA Cloning And Function Of The Key Gene BmSxl In Bombyx Mori

Study on sex determination in Bombyx mori was carried out for understanding the mechanism of sex determination and applying it in sericulture to bring some economic benefit. So study on silkworm sex determination has drawn attention in sericulture all the time. Classical genetics suggested that gene Fem on the w chromosome should be the primary signal in sex determination in Bombyx mori. Recently downstream regulatory gene Bmdsx has been identified. But gene network between genes Fem and Bmdsx is still unknown, especially genes regulating directly Bmdsx. With the finished draft sequence of silkworm genome, mechanism of sex determination in Bombyx mori was explored in our work after we studied different alternative splicing and different expression between male and female silkworm, and found the key genes by analysis of bioinformation, EST and the whole genome microarray. The main results present as follow. 1. Identification of homologs of sex-determining genes in silkworm genomeHomology analysis between the silkworm genome and all the known genes of Drosophila sex determination showed that homologs of 22 genes were found in silkworm. Moreover, their corresponding EST sequences were found except for gene Sxl. Homologs of sex determination were reported firstly after the draft sequence of silkworm genome came out.Analysis on the regulatory network of sex determination between silkworm and Drosophila indicated that, for the primary signal of sex determination, Homologs of genes da, emc, gro, sisB, run and dpn were found in silkworm while no one of genes her, sisA and sisC were found. This suggested that the ratio of X : A was not the primary signal of sex determination in silkworm but the single gene Fem, which was accorded with the point of classical genetics. In the dosage compensation pathway, no homolog of genes msl1 and msl2 were found while the one of the rest three genes msl3, mle and mof were found, which was confirmed that mechanism of dosage compensation is lacking in silkworm. In the pathway of sex determination of somatic cell, homologs of genes Sxl, tra2, dsx, ix, Rbp1, doa, snf, vir and fl(2)d were found except for tra, which demonstrated that sex determination in somatic cell should be conserved in silkworm though individual gene and its regulation may has changed. In the pathways of sexual behavior and sex determination in the germline, homologs of all the genes fru, dsf,ovo and otu found. This showed that both of pathways should be conserved in silkworm. In a word, in the regulatory network of silkworm sex determination homologs of most of downstream genes still work and were conserved. Homologs of only part of upstream genes work and something has changed. All this confirmed the idea that sex determination involved from the bottom of the regulatory network to the top proposed by Wilkins.