[Analysis of horizontal transfer gene of Bombyx mori NPV].

For research on genetic characters and evolutionary origin of the genome of baculoviruses, a comprehensive homology search and phylogenetic analysis of the complete genomes of Bombyx mori NPV and Bombyx mori were used. Three horizontally transferred genes (inhibitor of apoptosis, chitinase, and UDP-glucosyltransferase) were identified, and there was evidence that all of these genes were derived from the insect host. The results of analysis showed lots of differences between the features of horizontal transferred genes and the ones of whole genomic genes, such as nucleotide composition, codon usagebias and selection pressure. These results reconfirmed that the horizontally transferred genes are exogenous. The analysis of gene function suggested that horizontally transferred genes acquired from an ancestral host insect can increase the efficiency of baculoviruses transmission.

The complete mitogenome and phylogenetic analysis of Bombyx mandarina strain Qingzhou.

The complete nucleotide sequence of the mitogenome of Bombyx mandarina strain Qingzhou was determined. 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 B. 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.