The Complete Chloroplast Genome And Phylogenetic Analysis Of Fatsia Japonica And Hydrocotyle Sibthorpioides

Chloroplast,which originated from an endosymbiotic event in which ancient eubacteria invaded the eukaryotic cell,is an important organelle for its essential role in plant photosynthesis as biosynthetic factories.Furthermore,chloroplast DNA(cpDNA)conservativity and its slow rate of nucleotide substitution make cpDNA a suitable and widely used tool in plant phylogeny.Fatsia japonica and Hydrocotyle sibthorpioides,which are all belong to Araliaceae family,have potential or clear medicinal value and excellent gardening value as ornamentals.The chloroplast genome research about them can effectively supplement the plant chloroplast genome database,and contributes to related researchs such as intergeneric relationship among Araliaceae family.In the study,chloroplast genome sequences of F.japonica and H.sibthorpioides are reported for the first time,then we conducted comparative genomics analysis and phylogenetic analysis:(1)These chloroplast genome sequences are 155,613bp and 152,880bp respectively in length and have a typical quadripartite structure with large(LSC)and small(SSC)single-copy regions separated by a pair of inverted repeats(IRs).Their gene content and organization are considerably similar to those previously reported species belonging to the same family.We also analyzed their repetitive sequence,simple sequence repeats,codon usage bias and so on,which contribute to related researchs.(2)Results show that basic characteristics such as length of genome regions,GC content,gene content and organization are quite similar to other plants of Araliaceae,however,have interfamily and intergeneric differences.Particularly,ycf15 in h.sibthorpioides is a pseudogene.P-distance analysis shows the differences between these plants,as well as obvious tendency of group dividing.(3)We constructed phylogenetic trees basing on 22 kinds of chloroplast genomes of Apiales,using seven different data sets and by three methods.Results show that Hydrocotyle belongs to Araliaceae with strong support(100%)and forms the basal position of this family as the earliest diverging lineage;F.japonica belongs to Asian Palmate group of Araliaceae with moderate support,while we inferred it placed sister to a clade of Kalopanax septemlobus and Metapanax delavayi;the evolutionary relationship among Asian Palmate group tends to(((((K septemlobus+ M.delavayi)+ F.japonica)+(E.senticosus+ B.hainla))+ Dendropana)+ S.delavayi).This study enrichs the plant chloroplast genome database and whole genome database of corresponding plants.These phylogenetic trees based on chloroplast genomes can provide more phylogenetic data while in previous studies the number of taxa sampled was small and only provided limited resolution at the intergeneric level in core Araliaceae.Furthermore,the phylogenetic analysis using different data sets can be a good reference for datasets selection in subsequent analysis about,especially,lower-level evolutionary relationships such as intra-and inter-genera relationships.