Dissertation
Dissertation > Biological Sciences > Botany > Plant evolution and plant development

The Morphylogy, Genetic Diversity and Phylogenetic Analysis of Five Pseudo-nitzschia Species in Southeast China Sea

Author LinZuo
Tutor LiangJunRong;GaoYaHui
School Xiamen University
Course Hydrobiology
Keywords Pseudo-nitzschia nrDNA diversity the secondary structure of DNA phylogeny
CLC Q941
Type Master's thesis
Year 2008
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Pseudo-nitzschia is a diatom genus with species which are red tide causative species with world-wide distribution.The Pseudo-nitzshcia strains were isolated from Southeast China Sea and cultivated in lab.Morphological studies on Pseudo-nitzchia speices include the morphological observation under LM,SEM and TEM,and the description of morphological characteristics and classification.As for the molecular study,the SSU nrDNA、LSU nrDNA and 5.8S,ITS rDNA gene sequences were clones,sequenced and then used as DNA markers for genetic analysis and phylogenetic studies.The main purpose of this dissertation centered on following five aspects:the morphological classification,molecular identification,the interspecies and intra speices differences analysis,geographical genetic difference and phylogenetic relation.The main results were showed as follows:12 strains of Pseudo-nitzschia isolated from the coast of Southeast China Sea including,Holiday Bay of Hainan,Hongkong,Daya bay of Guangzhou,Xiamen,Taiwan Strait and Yangtse River estuary.According to the morphylogical charaters,five speices were identified:P.Pungens、P.cuspidata、P. multistriata、P.braziliana and P.delicatissima.Except for P.braziliana,other four speices are potential toxic species.Besides these 12 Pseudo-nitzehia strains,six toxic P. multiseries strains from Canada were also studied in this dissertation.The genetic diversity of SSUnrDNA,LSUnrDNA,5.8S rDNA and ITS were analysed and the phylogenetic tree based on these gene sequences were constructed The results show that:the average length of SSUnrDNA is about 1745bp which contains 103 varible sites and 44 informative varible sites;the average length of LSUnrDNA is about 822bp which contains 50 varible sites and 32 informative varible sites;the average length of 5.8S rDNA and ITS gene sequence is about 822bp which contains 439 varible sites of 1209bp including gaps and 401 informative varible sites of 1209bp including gaps.As a whole,the SSUnrDNA and LSUnrDNA gene sequences are more conservative and 5.8S rDNA,ITS gene sequence is more varible in Pseudo-nitzschia species.The LSUnrDNA of delicatssima exist relatively high diversity within the same spieces.Except for P.delicatissima,the genetic diversity of SSUnrDNA and LSUnrDNA within the same speices of Pseudo-nitzschia spieces in this study are relatively low.According to the CBCs analysis of the ITS-1 and ITS-2 of strains in this study,the P.pungens from Xiamen and Yangze estuary may form reproductive isolation.The secondary structure of ITS sequences were forcasted by Mold software on line and their CBCs were calculated by cbcsanalyzer software.According to the CBCs analysis of the ITS-1 and ITS-2of strains in this study,the P.pungens from Xiamen and Yangze estuary may form reproductive isolation.In the phylogeny study,the P.multisereis and P.pungens form monopoly respectively in all phylogenetic tree.And the P.cuspidata and P.psedudodelicatissima cannot be distinguished in all phylogenetic tree and form a complexity.According to the phylogeny tree,the phylogenetic relationship between the Nitzschia, Fragilariopsis and Pseudo-nitzschia were also explored.The results show that the phylogenetic relationship between Fragilariopsis and Pseudo-nitzschi is closer than that of Nitzschia and Pseudo-nitzschia.

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