Diversity Analysis Of Pyropia Ribosomal RDNA Gene Structure

Pyropia is a genus of red macroalga in intertidal zone, which is of great vaule ineconomical and social benefits.They can both reproduce sexually and asexually， andthe life history can be divided into gametophyte (fronds) and sporophyte (filamentous).This particular and complex life history makes it changing variably in evolution.It has been widely accepted that rDNA gene sequences as a DNA barcode toindentify and analysis the genetic diversity. However, many recent studies showedthat the high polymorphism existed in18S rDNA gene structure of interspecies andthe high variabilities were observed in ITS sequence of inter-individual among manyeukaryotes, which may affect the accuracy of phylogenetic analysis and geneticstructure.In this research, we studied the polymorphism of gene structure and ITSsequence of rDNA from P. haitanensis and P. yezoensis. The results were as follows.1. There is no intron in18S rDNA of individuals from cultured and wildpopulation of P. yezoensis. Their ITS sequences did not show a significantinsertion/deletion. No polymorphisms were observed in the EcoRV band pattern of18S rDNA-ITS-5.8S rDNA. These results indicated that the gene structure of18SrDNA-ITS-5.8S rDNA in intra-and inter-individuals selected in this research andthese individuals have closely relationships. The entire intergenic region of pyropiaappears to be folded in a manner which effectively brings all of the mature termini,the end of the18S rRNA, both ends of the5.8S rRNA andthe5’ end of the28S rRNA,into relative proximity, possibly constituting a single processing domain.2. The polymorphisms and variance existed in the gene structure of18SrDNA-ITS-5.8S rDNA from wild population of P. haitanensis. EcoRV restrictionanalysis shows that the variation generated in the downstream of18S rDNA region.Sequencing analysises showed group I intron were presented in downstream of1808position of18S rDNA from partial individuals and their size is554bp with51.1%ofGC content. The length of introns are similar and variance existed in the thesequences of different individuals. ITS sequences of different individuals did notshow the length polymorphism, but variance existed in their nucleotide sequence.Group I intron only disappear in18S rDNA from one strain of11strains of conchocells The extents of sequence variance between ITS1and ITS2are different,and UPGMA phylogenetic analysis based on ITS1and ITS2showed differenttopology sturctures.