Genic-SSR Markers Development And Population Genetic Study Of The Rare And Endangered Plant Tetraena Mongolica

Genetic variation is a product of long-term evolution and reflection of the adaptive capacity of species.The study of genetic diversity and genetic structure contributes to understand the evolutionary history of and fully dissect evolutionary potential,which is crucial for exploring the endangerment mechanism of rare species.Tetraena mongolica Maxim.,a xerophytic shrub with succulent leaves of the Zygophyllaceae family,is a rare and endemic plant to the Eastern Alxa-Western Ordos desert region in Inner Mongolia,China.T.mongolica is a good candidate for studies of biology diversity origin and habitat adaptation,because of a typical species with origin antiquity and strong stress resistance.In recent decades,the plant has suffered from human activities and environmental degradation,ecological environment and landscape pattern has occurred significant changes.The distribution area has been shrinking,the habitat environment has been fragmented,and the number of populations has declined sharply or even disappeared.Therefore,a lot widely attention from local governments and scholars has been made to the search of the conservation of this species and understanding of its genetic diversity and survival status.In this study,a gene expression database of T.mongolica was constructed by using transcriptome sequencing,and polymorphic genic-SSRs were identified by multiple transcriptome comparisons.Then,the quantity,frequency and location of the identified genic-SSR loci in relevant genes were characterized,and a group of polymorphism SSR markers was developed.Finally,the population genetics of this species was carried out by using the above developed genic-SSR markers,and ts genetic diversity and population dynamics were investigated from adults and seedlings groups.The main results are as follows:(1)A total of 343.2 million Clean reads were sequenced,and 119603All-unigenes were assembled,with an average length and N50 are 1098 bp and 1843bp,respectively.(2)A total of 811 polymorphic genic-SSR loci were identified in 646All-unigenes of six T.mongolica individuals.Among them,trinucleotides(522,64.36%)were the most abundant,followed by dinucleotides(261,32.18%).718genic-SSRs were successfully located in the related transcripts.The trinucleotide and dinucleotide repeats SSRs were mostly located in Protein-coding sequences(90.12%)and Untranslated regions(91.33%),respectively.(3)Functional annotation showed that genic-SSR-containing sequences were enriched in“Cellular processes”GO terms and“Plant hormone signal transduction”KEGG pathways,which indicates the SSR variance may have potential influence on the function of these genes.(4)Among 39 randomly selected genic-SSRs,32 were successfully amplified with the corresponding PCR products.These SSRs were showed some polymorphism in 48 T.mongolica individuals,which Observed heterozygosity(Ho),Expected heterozygosity(He),and Polymorphism information content(PIC)values were 0.462,0.579 and 0.518,respectively,and the polymorphic loci accounting for 82.05%of all the detected SSRs.(5)By using 12 highly polymorphic genic-SSR markers,363 individuals were explored to perform the population genetics study.As a result,there was no significant difference in genetic diversity among adults and seedlings groups,with the H_O and H_E of 0.428 and 0.509,0.435 and 0.526,respectively,and T.mongolica has a medium high level of genetic diversity,(6)The Genetic differentiation coefficient(F_ST)and Gene flow(N_m)values of the 14 investigated T.mongolica populations showed no significant variation on the populations that comprised adults and seedlings groups.The F_ST and N_m values were approximately 0.4 and 3.0,respectively.Then,the genetic structure of both adults and seedlings groups comprised populations were studied respectively,the result showed that both of them were divided into three clusters,and there were no significant changes in the genetic structure of these populations.