| Bangia are newly cultivated seaweeds in China, which have high nutritional value and medicinal value with great commercial importance. However, the species and distribution of Bangia in China had still not been understood clearly, and the genetic relationship between Bangia originated in freshwater and seawater is unknown yet. In this article, we investigated the species and genetic relationship between Bangia collected from the coastal areas and inland areas in China by clone and analysis ribosomal RNA gene sequence.Ribosomal RNA gene is composed of coding regions arid non-coding regions, coding regions including 18S rDNA,5.8S rDNA and 28S rDNA, and non-coding regions including ITS1 and ITS2 and IGS regions. Coding sequence is conservative, while non-coding region sequence evolutionary rate is faster. Due to the different evolutionary rate, ribosomal RNA gene is suitable for different levels classification. Through gene cloning and sequencing techniques, we sequenced and studied the ribosomal RNA gene sequence of marine Bangia sp. collected from Putian, Fujian province. The results showed that the length of 18S rDNA sequence is 2942 bp,5.8 S rDNA sequence is 158 bp,28S rDNA sequence is 3751 bp, ITS1 sequence is 699 bp, ITS2 sequence is 397 bp, and IGS sequence is 4613 bp. Therefore, the length of ribosomal RNA gene sequence Bangia sp. from Putian is 12530 bp.In this paper, we researched the phylogeny of Bangia sp. and collected nine marine samples from Weihai (WH), Shandong province, Lianyungang (LYG) and Nantong (NT), Jiangsu province, Putian (PT) and Nanridao 1-2 (NRD1-2), Fujian province and Nanao 1-3 (NA1-3), Shenzhen and two freshwater samples from Xinglongshan mount (XLS), Gansu province, Niangziguan(NZG), Shanxi province. Cloning and analysis of the 18S rDNA,5.8S rDNA and ITS region sequence,28S rDNA partial sequences and IGS partial sequences, the results showed that 11 samples from different regions were divided into three evolutionary branches:two freshwater samples clustered with freshwater samples from other parts of the world, and were independent from the marine samples; and nine marine samples were divided into two branches, the marine sample from Weihai (WH) was an independent branch, and the others marine samples were another branch. According to the latest revision of the international classification of 15 Bangiaceae genera, two freshwater samples were clustered in Bangia, the marine sample from Weihai were clustered in "Bangia" 1, eight marine samples were clustered in "Bangia" 2.We analysised different regions of the ribosomal RNA gene sequence of Bangia from different geographic groups, the results showed that the similarity of 18S rDNA sequence from different species was 89.0%-93.2% and 5.8 S rDNA sequence was 86.7%-90.5%, the similarity of the partial sequences of 28 S rDNA was 80.1%-86.2%, and the same species have a high similarity without significant difference. Therefore, the coding sequence is suitable for identification and classification of Bangia species.Although ITS region is extremely low sequence similarity between different species, it is very high similarity among intraspecies. So ITS region sequence should not be used for intraspecies analysis of Bangia, and it can be combined with 5.8S rDNA sequence for studying the classification of interspecific and above level. The partial sequences of IGS region from eight marine samples which clustered into the same evolutionary branch are almost no difference, so it is conjectured that the eight marine samples maybe the same speices. |
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