Analyze The Complete Nucleotide Sequence Of The Mitogenome Of Bombyx Mandarina And Study On The Mechanism Of Sex-linked Cocoon Fluorescence Color In Bombyx Mori

To fully understand the wild silkworm mitochondrial genome and analyze the origin of the silkworm. The complete nucleotide sequence of the mitogenome of Bombyx mandarina strain Qingzhou was sequenced and analyzed. The results showed that the circular genome is 15,717 bp long and has the typical gene organization and order of lepidopteran mitogenomes. All protein-coding sequences are initiated with a typical ATN codon, except the COI gene, which has a 4-bp TTAG putative initiator codon. Eleven of the 13 protein-coding gene have a complete termination codon (all TAA), but the remaining two genes terminate with incomplete codons. All transfer RNAs (tRNAs) have a clover-leaf structure typical of the mitochondrial tRNAs, and some of them have a mismatch in the four-stem-and-loop structure. The length of the A+T rich region of B. mandarina strain Qingzhou is 495 bp, shorter than that of B. mandarina strain Tsukuba (747 bp) but similar to that of Bombyx mori. Phylogenetic analysis based on the whole mitochondrial genome sequences of the available sequenced species (B. mori strains C-108, Aojuku, Backokjam, and Xiafang, B. mandarina strains Tsukuba, Ankang, and Qingzhou, and Antheraea pernyi) shows the origin of the domesticated silkmoth Bombyx mori to be the Chinese B. mandarina. Nuclear mitochondrial pseudogene sequences were detected in the nuclear genome of B. mori with the MEGA BLAST search program. A phylogenetic analysis of these nuclear mitochondrial pseudogene sequences suggests that B. mori was domesticated independently in different areas and periods.We also want to understand the different fluorescent cocoon between male and female, the strain of L, which cocoon fluorescence is sex-linked was investigated. The fluorescent pigments of the contents of midgut, midgut, blood, middle silk glands, posterior silk glands, and cocoon was analyzed with thin-layer chromatography (TLC), and showed a favourable consistency of the fluorescent pigments in its blood, middle silk glands, as well as cocoon. The difference fluorescent colour between the cocoon of male and female may caused by the yellow fluorescent pigments differently accumulated in the midgut of female and male. From the fluorescent regions on a native-PAGE gel separating total midgut protein of female, low weight 30kD lipoprotein, troponin, 30k lipoprotein and 27 kDa glycoprotein precursors were presumed to be some candidate of fluorescence-conjugated-protein by LC-MS identification. 2-D electrophoresis was also used to study the proteome of the hemlymph and the midgut between the male and the female of the same silkworm strain. Eventually, in the hemlymph, 61 special protein spots were identified from the male silkworm, and 15 special protein spots in the female silkworm, meanwhile, only were 153 special protein spots found in the midgut of male and 130 special protein spots in the midgut of female. Hopefully our results provided the valuable reference to the mechanism of the sex-linked cocoon fluorescence color between male and female.