| Sargassum is a collective name for the Ochrophyta,Phaeophyceae,Fucales,Sargassaceae and Sargassum.It is a type of large benthic brown algae grows widely in temperate and tropical sea areas around the world,while they are also distributed in coastal sea areas in China.Algae,as a unique group of organisms evolving from prokaryotic to eukaryotic,is the key to deciphering the origin and evolution of eukaryotes.And mitochondria and plastids originate from endosymbiotic pathways,their nucleotide or amino acid sequence data can be used for systematic evolutionary analysis.In addition,many structural features such as genome size,GC content,gene content,and genome collinearity can directly provide evidence for the origin and phylogeny of algae.Therefore,the determination of algae organelle genome is of great significance for studying the evolution and origin of organisms.This study used second-generation sequencing technology to analyze 8 common species of Sargassum in China,which including Sargassum horueri,Sargassum muticum Sargassum feldmannii,Sargassum mcclurei,Sargassum henslowianum,Sargassum graminifolium,Sargassum phyllocystum and Sargassum ilicifolium var.Conduplicatum.and sequenced and annotated their mitochondrial genomes.After inspection and calibration,the full length of mitochondrial genomes of 8 species of Sargassum were 34.6kb-34.9 kb.The structure is compact,and the number and types of coding genes are the same.The double-stranded encodes a total of 65 genes,including 35 protein coding genes(CDS),2 open reading frames(ORF),3 ribosomal RNA(r RNA),and 25 Transfer RNA(t RNA).No intron inserted in the mitochondrial genome of 8 species of Sargassum.The GC content of the entire mitochondrial genome of the 8 species in Sargassum genus was between 35.5%-36.7%,which was significantly lower than the AT content,which was consistent with the basic structural characteristics of other Sargassum's mitochondrial genomes.The base components all show strong G bias and T bias.In terms of codon usage,the mitochondrial genome of Sargassum algae is similar to most other brown algae and use the universal genetic code,and all protein coding genes use ATG as the the start codon,about 70% of the genes use TAA as the stop codon,about 20% use TAG as the stop codon,and about 10% use TGA as the stop codon.At the taxonomic level of the Sargassum family,we have performed systematic evolutionary analysis and collinearity analysis on the mitochondrial genomes of 16 species in 3 genera and 8 species in this study.The results showed that the mitochondrial genomes of Sargassoceae species all encode 65 genes,which are highly conservative in gene type and arrangement.Simultaneously,The phylogenetic tree construction of the mitochondrial genomes of 84 species of Phaeophyceae has been carried out.The results show that the species of Phaeophyceae are grouped together according to their respective groups,followed by Dictyotales,Fucales,Desmarestiales,Ectocarpales and Laminariales,It reveals the evolutionary process of brown algae from primitive algae to higher species,from simple to complex,and the genetic relationship between different groups.In addition,the Sargassum has two large branches according to subgenus Sargassum C.Agardh and Bactrophycus C.Agardh,which supported the existing classification system.In recent years,with the development of bioinformatics in various fields of molecular biology,organelle genomes have been widely used in the study of algae genetics and systematics.The development of study of mitochondrial genome and plastid genome are rapidly.To facilitate subsequent using and sharing of these data resources,we have organized and maintained them in a unified manner and converted them into a common standard data format.On this basis,we first established the algae organelle genome database website OGDA(The Organelle Genome Database for Algae,http://ogda.ytu.edu.cn),where can query the organelle genome and annotation information of various algae online,realize the visualization of genomic data,submit sequence for comparison,download related data files,and view the classification and distribution of each species on the website and different samples online.This website also can integrate a variety of applications to analyze the structural characteristics,collinearity and phylogeny of the algal organelle genome.The research on the structural characteristics of mitochondrial genome,comparative analysis of genome and phylogenetic analysis,as well as the construction of algae organelle genome database,provided molecular data and research platform for algae genomics and phylogeny research.At the same time,it laid the foundation for the genetic research and practical application of algae. |
PDF Full Text Request