| Gracilaria vermiculophylla belongs to Eukaryota, Plantae, Rhodophyta,Florideophyceae, Gracilariales, Gracilariaceae, Gracilaria. Gracilariavermiculophylla is widely distributed around the world, as well as in China’s coastalintertidal zone. It is one of the important raw materials for agar industry. It can also beused as bait mariculture and marine heavy metal adsorption. Recently, with the rapiddevelopment of genomics, more and more species’ whole genome have beensequenced, uncovering the mystery veil of genome. As the semi-autonomousorganelle of the cell, mitochondrion is characterized by multiple copies, small genomesize, and gene arrangement relatively conservative. In algae species mitochondrialgenome have been sequenced totally81consist in3empires (Chromista, Plantae,Protozoa),9phylums (Ochrophyta, Cryptophyta, Rhodophyta, Charophyta,Haptophyta, Chlorophyta, Glaucophyta, Choanozoa, Ciliophora). Mitochondrialgenome showed a great deal of diversity in the configuration, size, number of intron,repeats, stem-loop structure and clearly differences with green vascular plants.This study obtained two Gracilaria vermiculophylla’s mitochondrial genomecollected from Qingdao, China and Russia respectively for the first time in the world.The two Gracilaria vermiculophylla’s mitochondrial genomes’ DNA sequences isabout26kbp in length,72%in AT content. Genome annotation results of the twosample are basically the same:1ORF,24-coding genes,2ribosomal RNA (rRNA)genes,21transporter RNA (tRNA) genes, no intron insertion is found in all genes.Two transcription units are found which are separated in the transcription initiationsite and transcript in the normal chain and the negative chain in accordance with twotranscription polarities. Both of the two mitochondrial genomes use ATG as the startcodon, TAA as the stop codon (except atp8and rpl16use TAG as the stop condon).Unlike the standard genetic code, Gracilaria vermiculophylla use a different genetic code: TGA codon is translated as tryptophan (W). Mitochondrial genes’ mutation rateamong Gracilariaceae is between15%and55%, mostly in the20%or so. The twoGracilaria vermiculophyllas’ mitochondrial genes are very conservative:8genes arecompleted conserved, nad3mutation rate in the genus of up tp6.01%. Both in theRhodophyta and Gracilariales, the most conserved gene is cox1, the most variablegene is sdhC. The mutation rate of all genes within Gracilaria is lower than thatwithin Gracilariales and Rhodophyta.25bp overlap region is found between the secYand rps12. This structure has not been found in other algae. trn-His exists in bothGracilariopsis lemaneiformis and Gracilaria vermiculophylla mitochondrial genomes,but its location is different. As for Gracilariopsis lemaneiformis, trn-His is locatedbetween trn-Leu gene and cob gene. However, it locates between sdhB and trn-Glywithin Gracilaria vermiculophylla mitochondrial genome.The two BI trees based on the19common genes’ amino acid sequences of16redalgae and the18common genes’ amino acid sequences of57algae spcies show goodconsistency. The results of the phylogenetic trees can explain the chloroplastendosymbiosis theory very well. It can be concluded that the phylogenetic analysis ofmitochondrial genome can reflect the real evolution history of algae species. |
