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Genetic Markers For The Study Of Some Marine Microalgae

KrishiKosh

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Title Genetic Markers For The Study Of Some Marine Microalgae
 
Creator Saravanan V
 
Contributor Indrani Karunasagar
Karunasagar, I.
Venugopal, M.N.
Maragal, M.M.
Uduppa, K.S.
 
Subject dna, genetic structures, cloning, genetics, pcr, genomes, ecosystems, sampling, genes, locus
 
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.
 
Date 2016-07-04T14:19:14Z
2016-07-04T14:19:14Z
2007-04-12
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/68408
 
Language en
 
Format application/pdf
 
Publisher Karnataka Veterinary, Animal and Fisheries Sciences University, Bidar