The ITS2 genetic polymorphisms within Pseudo-nitzschia pungens (Bacillariophyceae)

Abstract

The bio- and genetic diversity of species could prevent the extinction from natural selection and provide the primary abilities to adapt to the various habitats. The pennate diatom, Pseudo-nitzschia pungens is cosmopolitan, and regarded asa common component of marine phytoplankton. The genetic diversity and distinct three genotypes (clades) of P. pungens have been studied quite enough, however the experimental proof of genetic polymorphism phenomenon has not been provided until now. We analyzed morphological features using LM and TEM images, and examined the ITS2 rRNA gene using genetically different (clade I and III) two parental and its two offspring P. pungens strains through cloning PCR. There were no morphological differences between parental and offspring strains, however the offspring strains showed recombinant sequences types in ITS2 region completely. The ITS2 sequences of offspring were composed by the sequences of clade I or III. Additionally, the high ratios (38.6 and 65.1%) of single nucleotide polymorphism (SNP) were observed in ITS2 region of offspring strains. Our results implicated that the genetic polymorphism phenomenon such as genetic recombination and SNP generation resulted from sexual-reproduction should contribute to maintain the genetic diversity and to produce the new genotypes within this species. Furthermore, the diverse hybrid types might provide adaptive strategies to various natural en