Zonggen Shen

Analysis of photosynthetic pigments and chlorophyll fluorescence characteristics of different strains of Porphyra yezoensis

The levels of photosynthetic pigments and chlorophyll fluorescence of Porphyra yezoensis strains selected from high-light environments were investigated. Sutong and Sulian strains originated from the same high-light environment but were selected from different sites on the Yellow Sea coast of Jiangsu Province, China. In January (a low temperature period), the Sulian strain and the WT (a widely cultivated strain) had higher levels of chlorophyll a, phycoerythrin, phycocyanin, and allophycocyanin, and higher actual photochemical efficiency of PSII (ΔF/Fm′) than the Sutong strain. This indicated that Sulian and the WT may have better adaptation to low temperature. In March (an optimal temperature period), Sutong had higher levels of photosynthetic pigments and higher ΔF/Fm′ than the WT and Sulian strains. This suggested that Sutong had higher light use efficiency at optimal temperatures and that most energy absorbed by PSII was used for photosynthetic electron transport. The differing areas of origin of these strains may have resulted in these differences in temperature adaptation.

Complete nuclear ribosomal DNA sequence amplification and molecular analyses of Bangia (Bangiales, Rhodophyta) from China

Filamentous Bangia, which are distributed extensively throughout the world, have simple and similar morphological characteristics. Scientists can classify these organisms using molecular markers in combination with morphology. We successfully sequenced the complete nuclear ribosomal DNA, approximately 13 kb in length, from a marine Bangia population. We further analyzed the small subunit ribosomal DNA gene (nrSSU) and the internal transcribed spacer (ITS) sequence regions along with nine other marine, and two freshwater Bangia samples from China. Pairwise distances of the nrSSU and 5.8S ribosomal DNA gene sequences show the marine samples grouping together with low divergences (00.003; 0–0.006, respectively) from each other, but high divergences (0.123–0.126; 0.198, respectively) from freshwater samples. An exception is the marine sample collected from Weihai, which shows high divergence from both other marine samples (0.063–0.065; 0.129, respectively) and the freshwater samples (0.097; 0.120, respectively). A maximum likelihood phylogenetic tree based on a combined SSU-ITS dataset with maximum likelihood method shows the samples divided into three clades, with the two marine sample clades containing Bangia spp. from North America, Europe, Asia, and Australia; and one freshwater clade, containing Bangia atropurpurea from North America and China.

Cloning and application of the complete nuclear ribosomal DNA (nrDNA) cistron sequence of Pyropia haitanensis (Bangiales, Rhodophyta)

Abstract Pyropia haitanensis (Bangiales, Rhodophyta)((T.J. Chang et B.F. Zheng) N. Kikuchi et M. Miyata) is a unique cultivar in China and the main problem with its cultivation lies in a lack of effective technology to distinguish intraspecific strains. In this study, we firstly obtained the complete sequence of rDNA of Pyropia haitanensis in China, which can help identify intraspecific variation within this species. The whole unit is composed of a small-subunit (SSU) rRNA gene with a full length of 2953 base pairs (bp) with two classes of introns and an exon sequence of 1837 bp; moreover, the complete sequence of the large-subunit (LSU) rRNA gene (length 4444 bp) also contains two introns; the length of the 5.8S rRNA gene is 158 bp; the length of internal transcribed spacers 1 (ITS1) is 334 bp and that of ITS2 is 678 bp; and the complete sequence of intergenic spacer (IGS) is 6969 bp. Some portions of the IGS sequences were used to analyze the similarities among five strains of Pyropia haitanensis; the sequence ranged from 4264 bp to 4273 bp and the G+C content was 53%. We also found 118 variable sites in the IGS which account for approximately 2.8% of the whole length. In conclusion, the nuclear ribosomal DNA sequence turned out to be an effective molecular marker for the taxonomic identification of Pyropia haitanensis.

Ribosomal intergenic spacer (IGS) sequence can distinguish varieties of Pyropia yezoensis cultivated in China

Abstract The ribosomal intergenic spacer (IGS) variation was compared for the nine main cultivated varieties of Pyropia yezoensis in China obtained from the Chinese National Pyropia Germplasm Repository. The full length of the IGS is 5984 bp including several sequence repeats and some complex structures. The sequence analysis of four partial IGS amplicons ranged from 3628 bp to 3776 bp; and the G+C content is 52.5%. Through similarity analysis and multiple sequence alignment of these partial IGS amplicons from the nine varieties, we have found 278 variable sites which account for approximately 7.5% of the whole IGS length. Both comparison of partial IGS sequences and phylogenetic analysis indicate high levels of genetic variation among different P. yezoensis cultivars in different areas of China. In comparison to the IGS of P. haitanensis, this study highlights the important function of classification of IGS in P. yezoensis. Therefore, the IGS sequence may be used to identify intraspecific variation in P. yezoensis.