Genome-wide Analysis Of Gene Evolution And Identification Of Horizontal Gene Transfer

Currently, available biologic sequence data are increasing exponentially with the completion of human genomic project (HGP) and the coming of the post genome era. It becomes a very important task in the study of bioinformatics to analyze huge dataset and obtain the valuable information. In this study, we described the application of two different levels by methods of bioinformatics.1. Genome-wide identification and evolutionary analysis of B7-H3B7-H3 is an immune costimulatory molecule of the B7 family that contains a set of immunoglobulin-V (IgV) and immunoglobulin-C (IgC) domains. By multiplex PCR, mouse B7-H3 was found to have an extracellular IgV-IgC domain (2IgB7-H3), whereas the dominantly expressed form of human B7-H3 was found to be a splice variant containing tandemly duplicated IgV-IgC-IgV-IgC domains (4IgB7-H3). Hamster B7-H3 was predicted to be 2IgB7-H3, and the monkey B7-H3 gene was predicted to have a similar structure to the human gene. To explore the evolutionary process of B7-H3 gene, we conducted a genome-wide structure and phylogenetic analysis of B7-H3 genes in currently sequenced genomes. Based on the available data, seventeen mammalian B7-H3 genes were predicted to have tandemly duplicated 4Ig domains. The analysis of gene structure and phylogenesis reveal that these 4IgB7-H3 genes resulted from domain duplication. Nevertheless, no difference in function has been observed between the two isoforms. It is likely that domain duplication in 4IgB7-H3 leads to functional redundancy.2. Analysis of Horizontal Transfer Gene of Bombyx mori NPVFor research on genetic characters and evolutionary origin of the genome of baculoviruses, three horizontally transferred genes were identified using the Blast search and phylogentic analysis method with Bombyx mori NPV and Bombyx mori genomic databases. These genes were origined from host insects, and the detected transferred directions are the HGT from insects to baculoviruses. The analysis results showed that baculovirus had obtained IAP and UGT gene through transfer of the transposon. There are 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 reconfirm that the horizontally transferred genes are exogenous. Interestingly, these genes are all known tobe directly involved in the infection of insect hosts by baculoviruses. These findings suggested that horizontally transferred genes accuired from an ancestral host insect can control host physiology and increase the efficiency of baculoviruse transmission.