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A forward genetic screen to identify factors that control meiotic recombination in Arabidopsis thalianaCoimbatore Nageswaran, Divyashree January 2019 (has links)
Meiotic recombination promotes genetic variation by reciprocal exchange of genetic material producing novel allelic combinations that influence important agronomic traits in crop plants. Therefore, harnessing meiotic recombination has the potential to accelerate crop improvement via classical breeding. Numerous genes involved in crossover formation have been identified in model systems. For example, SPO11 mediates generation of meiotic DNA double-strand breaks (DSBs) across all eukaryotes, which may be repaired as crossovers. However, downstream regulators of recombination remain to be identified, including those with species-specific roles. To isolate crossover frequency modifiers I performed a high-throughput forward genetic screen using EMS mutagenesis of Arabidopsis carrying a fluorescent crossover reporter line called 420. The primary screen isolated nine mutants from ~3,000 scored individuals that showed significantly higher (high crossover rate, hcr) or lower (low crossover rate, lcr) crossover frequency, including a new fancm allele. Four mutants (hcr1, hcr2, hcr3 and lcr1) were mapped by sequencing and candidate genes identified. The hcr1 mutation was confirmed as being located within the PROTEIN PHOSPHATASE X-1 (PPX-1) gene, using isolation of an independent allele and complementation studies. Similarly, the lcr1 mutation was confirmed to be within the gene TBP-ASSOCIATED FACTOR 4B (TAF4B). Using immunocytological staining I observed that hcr1 did not show changes in DSB-associated foci (RAD51), but it did show a significant increase in crossover-associated MLH1 foci. The hcr1 mutation increases crossovers mainly in the sub-telomeric chromosome regions, which remain sensitive to crossover interference. Also the genetic interaction between the hcr1 and fancm mutations is additive. These results support a model where PPX- 1 acts to limit recombination via the Class I interfering CO pathway, downstream of DSB formation. In summary, this genetic screen has led to discovery of novel genes that regulate meiotic recombination and their functional characterization may find utility in crop breeding programs.
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Functional proteomics : Generation and analysis of cDNA-encoded proteinsGräslund, Susanne January 2002 (has links)
No description available.
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Functional proteomics : Generation and analysis of cDNA-encoded proteinsGräslund, Susanne January 2002 (has links)
No description available.
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Effect of thermal regime on the expression of key reproductive genes during hormonally-induced vitellogenesis in female European eelsMazzeo, Ilaria 19 December 2015 (has links)
European eel (Anguilla anguilla, L., 1758) is suffering a strong
population decrease and at the same time it is a very appreciated
species and by now it has not been possible closing its cycle life. In
fact, this species does not mature in captivity unless hormonally
induced. So all the production is up to the natural population. All
these factors together make urgent achieving the closing of the
productive cycle and for this aim it is important to understand the
reproductive physiology and the reasons of this development
blockage.
The present thesis wants to be a new contribution to the knowledge
of reproductive physiology in female European eel submitted at
hormonal treatment. To achieve this goal, expression of genes not
previously studied in this species (cyp19a1, ara, arb, gnrhr1a,
gnrhr1b, gnrhr2, zpb and zpc) was analyzed in eels reared under a
constant thermal regime, accordingly to the usual rearing
conditions. Also, the effect of rearing temperature on gene
expression and steroid profile (T, 11-KT and E2) was studied. In
fact, eels migrate to Sargasso Sea to reproduce and during the
travel experiment temperature changes, while traditionally they are
reared at a constant high temperature which could affect
vitellogenesis progression and final oocyte quality.
For the study it was necessary cloning and characterizing some
genes which have not still been sequenced in European eel. Gene
expression was studied by qPCR after designing primer and
optimizing the qPCR race. Steroid profiles were analyzed by
immunoassays and the gonadal development stages were
established by histology.
The first result obtained at the end of the study were six new genes
characterized in European eel.
The analysis of gene expression allowed to understand the
involvement of specific genes during vitellogenesis (arb, gnrhr1b
and gnrhr2) in different brain regions.
The temperature was conformed as a crucial environmental factor
affecting vitellogenesis. On one hand, eels matured at lower starting
temperatures showed better reproductive parameters which could
have an influence in the final oocyte quality. On the other hand
higher temperatures are necessary to achieve further vitellogenetic
stages / Mazzeo, I. (2014). Effect of thermal regime on the expression of key reproductive genes during hormonally-induced vitellogenesis in female European eels [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48490 / TESIS
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