The Evolution Of Tufted Deer (Elaphodus Cephalophus) Inferred From The Mitochondrial Genome And Five Satellite DNAs

The species of Muntiacinae, Cervidae are morphological similarity but considerable diversity of their karyotypes, which are rare in the mammal evolution and great interest to evolutionary biologists and cytogeneticists. The tufted deer is a sole species in Elaphodus, Muntiacinae. Pervious reports showed that there was extreme chromosomal polymorphism in the species of Elaphodus cephalophus, including the 2n= 46/47/48 in female and 2n= 47/48 in male, but the evolution of its karyotypes and species is still unclear, So in the present study, we cloned the mitochondrial genome and five satellite. DNAs in the tufted deer, in order to research the chromosome evolution and species evolution.1. The mitochondrial genome of the tufted deer was determined by PCR. The mitochondrial genome (16 347bp) contains typical gene content and organization of mitochondrial genome found in mammals. Several unusual features distinguished this genome from other muntjacs mitochondrial genomes. The start codon of NADH4L appears to be GTG, which is rare in Cervidae, but has been designated as an initiator of Rangifer tarandus and Cervus nippon NADH4L. The cyt b gene (1143nt) has a subterminal AAA followed by the stop codon TAG. This is similar to that of Rangifer tarandus. Based on the 12 H strand protein-coding genes, phylogenetic analysis were carried out to confirm that a monophyly of Muntiacinae (Elaphodus + Muntiacus), the Elaphodus and Muntiacus were the sister-group relationships and the Elaphodus had diverged from Muntiacus species more than 4.3 MYA.2. C- values of male and female tufted deer was determined by flow cytometry using human lymphocyte cell DNA content (2C = 7.0 pg) as a standard. Result shows that DNA content for male and female are 4.962 pg and 4.971 pg, respectively. The genome size is 2.43×10~9 bp. The genome size of tufted deer is larger than that of Indian muntjac, but smaller than that of the Chinese muntjac, which had diverged later than tufted deer from the Muntiacinae subfamily. It's assumed that the tufted deer had evolved indepentently a relative long time.3. Five satellite DNAs were cloned and characterized by southern blot or Fluorescence in situ hybridization (FISH). FISH studies with satellite I and satellite II to different karyotype of tufted deer metaphase chromosomes localized both satellite DNAs at the pericentromeric regions of most of chromosomes. Two pairs of tufted deer autosomes (Chromosomes 1 and 2) had interstitial satellite I sites with a pair of these autosomal pairs (chromosomes 1) also exhibiting interstitial satellite II signals. An interstitial site on the X chromosome was found to have satellite I signals. These data were used to more precisely define the chromosome centrosome-telomere fusion and Robertson translocation in the tufted deer karyotypes.We also found that a X- autosome translocation in the tufted deer (2n= 47(?) ) . It drives karyotype evolution. The satellite III DNA family was isolated from the genome of roe deer and Chinese water deer, howerver, it was not detected among the other eight deer species examined from the genera of Alces , Cervus, Dama, Muntiacus, Odocoileus , and Rangifer. It is a relic of the 'old' deer species. In the present study, we generated a satellite DNA III clone from the tufted deer. FISH studies with satellite III to tufted deer metaphase chromosomes localized satellite DNA at the pericentromeric regions of a pair of small chromosomes. Therefore, it is also present in the genome of tufted deer. Southern blot studies with satellite IV to tufted deer genomic DNA demonstrated that Satellite IV also present in the tufted deer. It is a 'young' satellite DNA, not exist in the Chinese water deer. The Chinese water deer belongs to the Telemetacarpalia, but the tufted deer belongs to the Plesiometacarpalia. Take together, this might implicate that the tufted deer may be closely related to the ancestor of the Plesiometacarpalia (Cervinae and Muntiacinae). Southern blot studies with satellite V to tufted deer genomic DNA demonstrated that Satellite V also present in the male tufted deer. FISH studies with satellite V to tufted deer metaphase chromosomes localized on the pericentromere region and heterochromatin block on the long arm of Y chromosome. The heterochromatin might be amplified on the Y chromosome very recently. It further hints that the chromosomes evolution have more complex rearrangements in the Muntiancinae animals.