Polymorphism of MHC class IIB in an acheilognathid species, Rhodeus sinensis shaped by historical selection and recombination

Background Rhodeus sinensis is a bitterling species occurring throughout the numerous freshwater systems on the East Asia. Here, we analyzed the diversity of the MHC class IIB (DAB) genes from this species, which may offer meaningful insights into evolutionary processes in this species as well as other bitterlings. Results Using cDNA and gDNA samples from 50 individuals, we discovered classical 140 allelic sequences that could be allocated into either DAB1 (Rhsi-DAB1) or DAB3 (Rhsi-DAB3). DAB sequences completely lacking the intron, but identical or similar to Rhsi-DAB1, were also discovered from our gDNA samples, and this intron loss likely originated from the retrotransposition events of processed mDNA. The β1 domain was the most polymorphic in both Rhsi-DAB1 and -DAB3. Putative peptide biding residues (PBRs) in Rhsi-DAB1, but not in Rhsi-DAB3, exhibited a significant dN/dS, presumably indicating that different selection pressures have acted on those two DABs. Recombination between different alleles seemed to have contributed to the increase of diversity in Rhsi-DABs. Upon phylogenetic analysis, Rhsi-DAB1 and -DAB3 formed independent clusters. Several alleles from other species of Cypriniformes were embedded in the clade of Rhsi-DAB1, whereas Rhsi-DAB3 clustered with alleles from the wider range of taxa (Cyprinodontiformes), indicating that these two Rhsi-DABs have taken different historical paths. Conclusions A great deal of MHC class IIB allelic diversity was found in R. sinensis, and gene duplication, selection and recombination may have contributed to this diversity. Based on our data, it is presumed that such historical processes have commonly or differently acted on the polymorphism of Rhsi-DAB1 and -DAB3.

Crystalline-like structure in sperm membrane of Chinese Rhodeus sinensis, Acheilognathinae

It is well know that the spermatozoa are highly polarized cells. The membrane of mammals sperm have been studied in detail. The results have shown are markable diversity of structure with in an otherwise common place unit membrane. However, very few papers were dealt with teleost sperm membrane. Our privious report shows that Carassius auratus (Cyprinidae) sperm membrane have differentiated with regional specificity just like those in mammals. In general, intramembrane protein particles are highly organized at certain are as in the head plasma membrane forming crystalline-like structure, in contrast, rest areas of plasma membrane contain many random dispersed particles. The present study has shown the existence as well as the characteristics of crystalline-like structure in sperm membrane of Chinese Rhodeus sinensis, Acheilognathinae, Cyprinidae.In spawing season the male fish are killed, apart of test is were took out and put into 2.5% glutaraldehyde buffered to pH 7.2 with 0.1mol/L sodium cacodylate.