Genetic Markers For The Study Of Some Marine Microalgae
KrishiKosh
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Title |
Genetic Markers For The Study Of Some Marine Microalgae
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Creator |
Saravanan V
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Contributor |
Indrani Karunasagar
Karunasagar, I. Venugopal, M.N. Maragal, M.M. Uduppa, K.S. |
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Subject |
dna, genetic structures, cloning, genetics, pcr, genomes, ecosystems, sampling, genes, locus
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Description |
Ph.D. Thesis
Skeletonema is a diatom genus which is wide spread all over the world’s oceans. It is one of the dominating phytoplankters in temperate regions. In many parts of the world, Skeletonema is commonly found throughout the year, but in temperate regions the highest density occurs during spring blooms. Recent studies have examined S. costatum-like species using electron microscopy, and the small and large subunit rRNA genes. The diatom S. costatum has recently been emended and several new species have been described. One of these is S. marinoi, which is a cosmopolitan organism that contributes significantly to phytoplankton blooms in temperate waters. S. marinoi is an important primary producer occurring world-wide in high abundance in both plankton and benthos; thus, scientific studies of this organism are of ecological significance. In this study, we have identified and amplified two microsatellite loci using the primers designed from the sequence data generated. The developed primers were standardized for the identified microsatellite regions. Thus, for the first time we have developed two highly stable and polymorphic microsatellite loci in the S. marinoi genome. We have used several S. marinoi samples to determine the number of alleles and also allele positions at the two identified microsatellite loci. In this study, we have also evaluated the utility of three common molecular methods for distinguishing clones of S. marinoi from different geographic regions. Clonal cultures were isolated from Canadian west coast, south-west Portugal and the east and west coasts of Sweden. All the strains originated from the resting stages in sediment. Genetic signatures of clones from each sample location were assessed by sequencing variable domains (D1-D3) of the nuclear large subunit (LSU) rRNA gene and internal transcriber spacer (ITS1, 5.8S and ITS2) regions and also by analysis of RAPD patterns. Analysis of molecular variance showed that strains from four geographic areas were significantly separated by all the three methods but differences in European samples were best resolved by ITS 2 sequences. Auxospore formation has been observed in single clonal cultures; hence it is known that sexual recombination occurs. But it is not known if Skeletonema sp is homothallic or heterothallic. AFLP was used in the analyses of genetic variation at the sub-species level. An intercrossing experiment was set up with two parental clones of Skeletonema sp isolated from plankton samples collected off the coast of Mangalore, India one year apart. The parental clones were mixed and from the mix, F1 generation was isolated. There was high reproducibility and results of the experiment showed a similarity value of 93% or higher which was strong indication of identical clones, while similarity ranging from 73% to 90% indicated homothallic recombination. Heterothallic reproduction gave similarity values of 60% to 70% and different clones of Skeletonema were less than 60% similar. In this study, we also report the seasonal distribution of S. marinoi in Gullmar Fjord on the Swedish west coast. Monoclonal cultures were established throughout the year and pre-adapted to identical culturing conditions. The purpose was to investigate if clones of S. marinoi isolated from different seasons exhibited physiological differentiation and if it could be coupled to genetic heterogeneity. We also investigated if physiological variations among groups of clones are stable when environmental parameters are changed. The physiological parameters examined were maximum growth rates, maximum cell abundance and RNA content per cell. |
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Date |
2016-07-04T14:19:14Z
2016-07-04T14:19:14Z 2007-04-12 |
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Type |
Thesis
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Identifier |
http://krishikosh.egranth.ac.in/handle/1/68408
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Language |
en
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Format |
application/pdf
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Publisher |
Karnataka Veterinary, Animal and Fisheries Sciences University, Bidar
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