Complete Organelle Genomes Of Bangia Fuscopurpurea OUCPT-01 And Bangia Atropurpurea:Insights Of Origin Of Bangia Atropurpurea By Organelle Phylogenome Analysis

Both Bangia fuscopurpurea and Bangia atropurpruea are classified in Rhodophyta, Rhodophyceae, Bangiales, Bangiaceae. Evolution and classification of Bangiaceae algae has always been highly concerned and the issue on the relationship between freshwater and marine Bangia algae has attracted more attention. Until now, both freshwater and marine Bangia algae organelle genomes which possess important evolutionary information are still obscured. In order to explore the organelle genomes’ structure and gene content of freshwater and marine Bangia algae as well as to make progress in understanding the relationship between the two Bangia species, using the advanced second generation sequencing technologies and utilizing different assembly strategies, organelle genomes of two Bangia algae with entire different living environment were determined at first time. Comparative genome analyses and phylogeny analyses based on whole organelle genomes were implemented, and we inferred the divergence time among Bangiaceae algae.The main results and conclusions are as follows:(1) Established complete assembly work flow of Baniaceae organelle genomes.(2) Affirm that the marine specie (Bangia fuscopurpurea OUCPT-01) collected from coastal line of Putian, Fujian Province belongs to typical marine Bangia taxa (’Bangial genera) and freshwater specie (Bangia atropurpruea) collected Niangziguan, Shangxi Province belongs to typical freshwater Bangia taxa (Bangia genera).(3) Sizes of Bangia fuscopurpurea OUCPT-01 chloroplast and mitochondrial genomes are 196,913 bp (GC content:33.9%) and 43,517 bp (GC content:32.4%), respectively. Sizes of Bangia atropurpurea chloroplast and mitochondrial genomes are 189,505 bp (GC content:32.4%) and 35,679 bp (GC content:30.9%), respectively. Except the difference of ORF number and length, gene content encoded by the two chloroplast genomes are identical. Sharing average 86% similarity, the two chloroplast genomes also own high identical collinearity degree. Both mitochondrial genomes encode same core genes, display similar gene order, but their introns number, position, length are distinctive.(4) Improved and established a rapid alignment method using whole organelle genome sequences.(5) tmRNA found in chloroplast genome of Bangiaceae algae proved to be an efficient phylogenetic marker with resolution on genus level. Phylogeny analyses, based on whole organelle data of sequenced red algae, indicated Bangia atropurpurea a close genetic relationship with Porphyra algae. Bangia fuscopurpurea OUCPT-01 clustered into one branch with Bangia atropurpurea and Porphyra algae, displaying a far genetic distance with Pyropia clade.(6) Divergence time was inferred according a calculated fossil time node. The results depicts that divergence time of Bangiaceae algae mainly distributed from 400-100 million years ago. The divergence of Bangia atropurpurea and Porphyra algae happened in Permian geological time (when Paleotethys Ocean became inland sea and Hercynian movement happened on old China continent). Combining the result and phylogeny analysis, it indicated that, Bangia atropurupea collected from Niangziguan, Shanxi province, most possibly, originated from marine species.