The Complete Chloroplast Genome And Phylogenetic Analysis Of The Endangered Species Syringa Pinnatifolia (Oleaceae)

Chloroplasts are the photosynthesis organelles of plants,and are an important unit of plant cell genetics.The chloroplast genome sequence of angiosperms is highly conserved and belongs to the maternal inheritance.It has many advantages such as small molecular weight,simple structure,low evolution rate and multiple copies.Therefore,The complete genome research of chloroplasts is becoming more and more important in the study of plant genomics.Syringa pinnatifolia is a National Grade III Endangered Species,and is the only plant with pinnately compound leaves in the Syringa genus,It has important scientific significance for studying the genetic relationship,phylogeny and geographical distribution of Syringa.However,there are few studies on the chloroplast genome of S.pinnatifolia,which hinders the development of molecular biology and genomics.This paper first published the chloroplast genome of S.pinnatifolia.In this thesis,the optimal method for extracting chloroplast DNA from S.pinnatifolia was obtained.The full-length chloroplast genome of S.pinnatifolia was obtained by high-throughput sequencing,and its genomic structure was analyzed and compared with its related genomes.These contents enrich the study of the chloroplast genome of the S.pinnatifolia,and have important value for the development of its molecular markers,phylogenetic relationships,chloroplast genome engineering and its endangered mechanism.The main results are as follows:(1)In this paper,two representative plants of the genus Syringa were selected,including the endangered species S.pinnatifolia and the widely distributed S.oblata,and the chloroplast separation and chloroplast DNA extraction methods were compared and analyzed by modified high-salt low-p H method.High purity and quality chloroplast DNA conforming to genomic molecular level studies was obtained,and a simple and rapid method for chloroplast DNA extraction was established.(2)The High-throughput sequencing technology was used to sequence and analyze the chloroplast genome of S.pinnatifolia.The bioinformatics software was used to assemble and splicing the chloroplast genome to a total length of 155,326 bp,and have a typical quadripartite structure composed of a large single copy(LSC)region,a small single copy(SSC)region,and two inverted repeats(IRa/IRb).The sequence and content of the genes are similar to the published chloroplast genome of the Oleaceae plant.Furthermore,the GC content,the IR expansion and contraction,the long repeat sequence,the simple repeat sequence,and the codon usage bias were analyzed for S.pinnatifolia and its related plants,which provided basic data for the subsequent research of the plant.(3)35 species of Lamiforms and Gentianales plants were selected.Arabidopsis thaliana was used as the outer group.The phylogenetic tree was constructed by using different chloroplast genome datasets.The obtained phylogenetic tree has accurate subject position and high support rate.The results showed that the Oleaceae plant and the Lamiforms formed a lineage,and the relationship between S.pinnatifolia and Syringa vulgaris and Ligustrum lucidum was similar.The lineage were formed separately from the other Oleaceae species,and S.pinnatifolia were earlier differentiated from Oleaceae.The evolutionary relationship and location of the cloves in the angiosperms were elucidated.These results provide the basis for a complete phylogenetic analysis of the Syringa.