Mapping Of Z~∧W Translocation Chromosome Fragment And Analysis Of Functional Genes In The Sex-Linked Balanced Lethal Silkworm Strain

Sex-linked balanced lethal (SLBL) silkworm strain was bred by Strunnikov with irradiation in 1975. The males of the SLBL strain has two non-allelic recessive genes (lethal gene 1,l1and lethal gene 2,l2). The two genes are located on two different Z chromosomes and cause death at embryo stage. There are two translocated fragments on the W chromosome. One fragment was from 10th chromosome containing the egg colour gene (+W2), which can cover up the white egg colour mutation (w2). The other was one from the Z chromosome, which conteins the +os gene that can compensate the os (larval skin translucent) mutation and rescue the lethal effect of l1 on the Z Chromosome. In the SLBL strain, the female eggs are black and the male eggs are white, which could help us to distinguish the sex of silkworm during the egg stage. Half of the male and female embyroes will die during the embyro stage due to the l1 and l2, respectively. In present research, the simple sequence repeats (SSR) were employed as a tool to analyze the Z(?)W translocation fragments to provide a theoretical basis for molecular regulation mechanisms in the SLBL strain.The results are as follows:563 pairs of SSR primers were designed based on the conserved sequence of Z chromosome (near to os) of P50 strain, and used to detecting the polymorphic markers between the SLBL strain (female parent, P1) and the wild silkworm strain (male parent, P2).124 markers showed polymorphic between the parents. The F1 and BC1 generation were made using P1 as female parent and P2 as male parent. The female moths of F1 and both female and male moths of BC1 were used for selecting the W-linked markers. 26 SSR markers were amplified with double-bands among the female moths of F1 generation and were used for selecting the sex-limited inheritant markers in the BC1.5 SSR polymorphic loci were linked with W chromosome including Bm_scaf72-2, Bm_scaf72-32, Bm_scaf72-37, Bm scaf72-45 and Bm scaf72-55. It indicates that these markers were located on the Z W translocation segment. The length between Bm_scaf72-2 and Bm_scaf72-55 is about 0.48Mb. While Bm_scaf72-87 marker has no sex-limited inherited character in F1 and BC1 generation. The translocation site was located between Bm scaf72-55 and Bm scaf72-87 about 0.32 Mb.The function of the genes in the translocation range betweem Bm_scaf72-2 and Bm_scaf72-87 were analyzed by bioinformatics methods. And the length between Bm_scaf72-2 and Bm_scaf72-87 is about 0.8Mb. The results showed that some important genes playing the key role in biological activity were contained among these regions, including G-protein signaling modulator, cycle like factor, ociad protein, PAR-domain protein, amino acid transporter, olfactory receptor-like receptor, cl-channel protein, H+ transporting ATP synthase, and phenylalanine hydroxylases.