| SSR polymorphism and mitochondria! DNA length variation and heteroplasmy in the population of Chinese alligator (Alligator sinensis) were studied in the present research.1 The technique of microsatellites DNA markers and its application in conservation genetics of endangered animals Microsatellites DNA are simple tandemly repeated sequence motifs consisting of repeat units of 1-5 bp in length. As genetic markers, they are widely dispersed in eukaryotic genomes. The advantages of microsatellites include high polymorphism, high abundance, codominance and selective neutrality. In present review, the primary principle, researching methods, main characters and technology development of microsatellite DNA makers were summarized, and its applications in the genetic conservation of endangered animal were illustrated.2 SSR polymorphism of Alligator sinensis and conservation strategy of genetic diversity In order to reveal the genetic structure of Chinese alligator population, total of 39 individuals including 7 wild individuals outside of the research center were sampled to construct wild, F1 and F2 groups according to their generations, and 10 micorsatellite loci selected from 25 primer pairs originally designed for Alligator mississippiensis were employed for investigating the genetic diversity of Alligator sinensis. The results indicated that contrasting with Alligator mississippiensis and some other endangered species, Chinese alligator had a extremely low genetic diversity level with ,4=2.38, Ne=1.60, H0=0.374, He = 0.350 and PIC=0.327. There were no significant differences of A, Ne, H0, He, PIC and each SSR locus alleles frequency distribution among 3 groups. However, Hardy-Weinberg equilibrium analysis revealed that F2 captive group showed a remarkable genetic disequilibrium at loci Ami-#,-6 and Ami-#-222. The reason accounting for the current genetic status ofXChinese alligator is dramatically shrink of the population in past decades. Due to the lack of significant difference between wild group and captive group, all survived Chinese alligator should be treated as one ESU in the next conservation practice. More attention regarding the effective population size and low frequency alleles should be emphasized in genetic management of captive alligators and establishing new separated propagation.3 Mitochondrial DNA Length Variation and Heteroplasmy in Captive Populations of Chinese Alligator Due to the severe population shrink and depression in past decades, Chinese alligator was in very poor genetic diversity status which was revealed by RAPD, AFLP, SSR and mtDNA sequencing. However, apparent variance of fragment length was found in tandemly repeated region of mtDNA control region 3' end, 12 haplotype fragments and 21 genotypes were detected in 48 individual samples, and there were 12 individuals exhibited heteroplasmy that 2~4 fragments were detected in their amplification products respectively. Compared with other molecular makers, the high variance revealed by mtVNTR might be attributed to the apparent difference of the genetic diversity recovery at different lever despite the individual number recovered obviously in Chinese alligator captive populations which were set up sooner after the severe bottleneck, and also relate to its special composition in tandemly repeated sequences. The heteroplasmy detected in some individuals indicated that the mechanisms of mtDNA replicating and inheriting might be more complicated than we know, and it is necessary to carry out further research to determine the exact reason for length heteroplasmy of mtDNA detected in Chinese alligator.4 The individual identification of Chinese alligator with SSR and mtVNTR To prevent the genetic depression of Chinese alligator and keep its existing genetic diversity, it is necessary to carry out individual identification and screening for rare alleles and their holders. SSR and mtVNTR markers were applied to discriminate 39 Chinese alligator individuals, and the result showed th...
|
PDF Full Text Request