The Complete Mitochondrial Genome Pyropia Haitanensis And Pyropia Yezoensis

Pyropia haitanensis and Pyropia yezoensis are commercially very importantseaweeds in China. As the representatives of rhodophytes, the origin, evolution andenvironment-stress of them have attracted great attention. They are of greatimportance in scientific research as the model species for studying the physiology andmolecular genetics of seaweeds. Unfortunately, the knowledge of their genomes isvery little, especially to the mitochondrial genomes which are essential in the energymetabolism. In order to gain insight into the composition and structure characteristicsof mitochondrial genomes from P. haitanensis and P. yezoensis and explore thephylogeny of rhodophytes, we sequenced the complete mitochondrial genomes of thetwo important species and the full sequences of them were acquired with somedetailed bioinformatic analysis. The major results are as following:1. The complete mitochondrial genome of P. haitanensis which is acircular-mapping molecule was determined to be37,023bp. The overall AT content ofthe genome is69.32%. It contains23protein coding genes and5open reading frames(ORFs),2ribosomal RNA genes and24transfer RNA genes. It has four group IIintrons, two are situate in the large subunit rRNA genes (rnl) gene and the other tworeside in cytochrome c oxidase subunit1gene (cox1). Each of the group II intron hasan ORF inserted. The origin of replication of the mitochondrial genome is betweentrnQ and trnSec and the terminal is located between trnA and trnR. All theprotein coding genes and ORFs have typical ATG start codon, except for cox1and cox2, which contain the unusual GTG and CTG as an initiator codonrespectively.2. The complete nucleotide sequences of the circular mitochondrial genome fromP. yezoensis was identified to be41,688bp and the overall AT content is67.28%.There are total of61genes, including23protein coding genes and9ORFs,2rRNAgenes and27tRNA genes. There are five group II introns in the genome, two are inserted into the rnl gene and the other three in cox1gene. All the five group II intronshave a classical ORF respectively. The replication of the mitochondrial genomeinitiates between trnQ2and trnSec and terminates between trnA and orf53. Thegene of cox1, like the mitochondrial genome of P. haitanensis, has a GTG startcodon, but TTG serves as a start codon in the gene of cox2.3. P. haitanensis and P. yezoensis previously placed in the genus of Porphyra arenow belonging to the new genus Pyropia.4. The deduced amino acid sequeces of13protien coding genes from24specieswere used to construct the phylogenetic trees based on neighbor joining method andmaximum likely hood method as well as bayesian inference method. The results are:The rhodophytes are monophyletic group and they are not direct sister group ofchlorophytes and land plants. But the genetic relationships of them are very closecompared to the phylogenetic relationships between rhodophytes and the group ofdiatoms, golden algae and brown algae. In the phylogenetic tree of neighbor joiningand bayesian inference, red algae and cryptophytes clustered together, suggesting thatthey are two closely related lineages.