The Research On The Immunoglobulin Heavy Chain Sequences Of Hucho Taimen

Hucho taimen taxonomically belongs to Osteichthyes (Osteichthyes), ray-finned (Actinopterygii),Clupeidae catalogue (Clupeomorpha), order salmoniformes (Salmoniformes):(Salmonoidei), salmon, salmon branch?(Salmonidae), salmon, Salmo subfamily(Salmoninae)(Salmo).Hucho taimen can naturally grow very big and fast, and the meat of the fish is delicious and nutritious. There are2subspecies in cold aquatorium inland of our country, with the difference of anadromous form population and totally freshwater habitat population.Fish are the earliest creatures having immunoglobulin (Ig). The immunoglobulin gene sequences showed great changes in evolution boundary of fish, and Salmonidae fish originated in a special geographical period, therefore the study of immunoglo-bulin gene sequence of salmonids, has important meaning to many aspects such as palaeobiogeography, palaeoecology, climate change and vertebrate evolution system. In this regard, hucho taimenimmunoglobulin heavy chain variable region (VH) and constant region (CH) sequences have been studied and functionally analysed by using the molecular biology and Bioinformatics Method, and compared with therainbow trout(Oncorhynchus mykiss) corresponding sequence (Genbank accession No. S63348.1)for similarity.From the main immune organs of hucho taimen, spleen, total RNA were extracted, and RT-PCR techniques were used for the heavy chain cDNA clones.40clones were selected randomly from positive clones sequenced.32complete VH sequences without repeating and1CH sequence were obtained. Through the BLUST network comparison, the result showed that the sequences similarity reach up to87.4%between the hucho taimemmmunoglobulin VH and the sequence with GenBank accession number S63348.1. Domain variability analysis of the nucleotide sequence obtained showed that the framework region (FR) of hucho taimen immunoglobulin HV is relatively conservative, with low mutation rate. Complementary determining region (CDRs) mutation rate is high, especially in CDR3area, that can reach up to35%. In immunoglobulin VH, random rearrangement of D and J fragments, exonuclease function, as well as lots of N, P fragments inserting in heavy qualifying point, have greatly increased the diversity of the heavy chain variable region of hucho taimen Ig. Compared with the corresponding sequences of Channel catfish(Ictalurus punctatus),Grass carp(Ctenopharyngodon idella), Rainbow trout(Oncorhynchus mykiss) and Atlantic salmon(Salmo salar), the constant region of hucho taimen displayed closely genetic relationship with of Rainbow trout and Atlantic salmon. The Ig obtained in the study was inferred to be type of IgM.