Saudi Cultural Missions Theses & Dissertations
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Item Restricted Genetics of Heat Tolerance in the Bengal and Assam Aus Panel of Rice(University of Aberdeen, 2024-07) Alonazy, Dalal; Price, Adam; Norton, Gareth; Barker, MartinRice (Oryza sativa L.) is considered as the main stable food and largest grain crop in many Asian countries since they rely on it for basic nutrition. During the past few years, the temperature in rice-growing regions has been rising, and extreme high temperature events are increasingly frequent, potentially causing crop damage. Heat stress caused by rising temperature over the optimal range is a significant abiotic stress affecting rice production. Heat stress can negatively affect plant growth, development and productivity, causing a loss of yield. Therefore, developing heat tolerant rice varieties is essential. In this work, heat tolerance was evaluated in 204 rice cultivars, mostly from Bengal and Assam Aus Panel (BAAP). High heat tolerant genotypes were identified using two approaches: spikelet fertility and chlorophyll fluorescence. For spikelet fertility, the heat tolerant genotypes identified were ARC 14965, ARC 10392 and Goria. For chlorophyll fluorescence, the genotypes identified were KALI AUS, Code No BI 93 and AUS 130. Genome-wide association (GWA) mapping was conducted on the heat tolerance trait with two million SNPs using an efficient mixed model (EMMA). The total number of QTLs associated with traits related to heat tolerance identified were 23 in fertility trait and 10 QTLs in photosynthetic trait. A number of these QTLs contained functional candidate genes. A total of seven candidate genes were identified for control/treatment ratio; SEC14, Hsp20, AP2/ERF, WRKY28, miRNA156, OsDjC56 and ZOS6-06 and three for QY trait after 60 minutes; PHD13, OsSTA65 and CGN. Additionally, RNA-sequencing analysis (RNA-seq) was conducted on spikelet fertility trait and well-known heat tolerant genes were detected such as (OsMYB55, OsHTASb and OsHSFC1b). Through the combination of GWA and transcriptomic analysis two excellent candidate genes associated with heat tolerance in rice were identified, namely; miRNA156 and OsDjC56. In addition, the candidate gene CGN in the leave study differentially expressed in the RNA-seq. In conclusion, the heat tolerant genotypes and QTLs and candidate genes identified in this study could be serve as valuable resource for further advanced research in rice heat tolerance and for breeding programs aimed at enhancing sustainable rice production. Such work could make an important contribution in supporting global food security worldwide.26 0Item Restricted STUDIES ON ZEBRAFISH THROMBOCYTES(University of North Texas, 2024) Fallatah, Weam; Jagadeeswaran, PudurZebrafish thrombocytes exhibit characteristics of human platelets and megakaryocytes, making them valuable for studying megakaryopoiesis and thrombopoiesis. Using single-cell RNA sequencing, we analyzed gene expression in young and mature zebrafish thrombocytes. We identified 394 protein-coding genes unique to young thrombocytes, many corresponding with human orthologs, suggesting shared regulatory mechanisms in zebrafish and humans. We hypothesized knocking down these 394 genes should identify the novel regulatory genes that control thrombocyte maturation. To address this, we used the piggyback knockdown method to knock down these genes to study their biological functions in zebrafish thrombopoiesis. We first found the knockdown of nfe2, nfe2l1a, and nfe2l3 reduced both young and mature thrombocyte counts, confirming their role in thrombopoiesis. A comprehensive knockdown screening of the uniquely expressed genes in young thrombocytes identified 7 candidate genes associated with thrombopoiesis. We selected the spi1b gene for further mutant characterization, which revealed its critical role in young thrombocyte development, with homozygous mutations leading to embryonic lethality. Considering megakaryocyte properties in thrombocytes, we studied the potential for polyploidization in zebrafish thrombocytes. The inhibition of AURKA led to the development of polyploid thrombocytes resembling mammalian megakaryocytes, suggesting the retention of genetic programs for megakaryocyte development in zebrafish thrombocytes and providing insights into the evolutionary basis of thrombopoiesis. Thus, our study reveals critical gene expression patterns and regulatory factors in zebrafish thrombocyte development, offering insights into conserved mechanisms relevant to developmental biology and research in thrombosis and hemostasis disorder.21 0Item Restricted The biological significance of genetic variation in arbuscular mycorrhizal colonisation in rice(University of Aberdeen, 2024-01-11) Sumayli, Mari Mohammed; Price, AdamA variety of crops, including different types of rice, are colonised by arbuscular mycorrhizal fungi (AMF), which possess the ability to effectively absorb essential nutrients, such as phosphate, from the surrounding soil. The utilisation of mycorrhizal symbioses in agricultural systems is a highly promising strategy for the development of resource-efficient and ecologically sustainable agricultural practises. AMF colonisation with rice tends to be low under flooding regimes due to the domination by anaerobic processes. However, understanding rice-AMF interaction under non-flooded conditions is of key importance for improving nutrient and water use efficiency. AMF colonisation by Rhizophagus irregularis in rice showed a wide range of genetic diversity. This work seeks to determine the biological significance of that variation. Five cultivars were selected because of consistent differences in colonisation. By using three pots with different mesh exclusion systems, AMF (R. irregularis) and rice roots were orientated to the supply of phosphate, where calcium hydrogen phosphate (CaHPO4) was either inaccessible (solid barrier “control”), accessible only to the AMF (20 μm mesh) or accessible to both the AMF and rice roots (2 mm mesh). We found significant differences in plant heights, tillers, biomass, and AMF colonisation across all our pot systems. There was a big genetic difference in AMF colonisation. AMF colonisation was limited in 2 mm mesh compared to control and 20 µm mesh. A massive increase of P uptake in 20 μm mesh demonstrates AMF-driven P acquisition. However, naturally inoculated (Soil) experiments revealed lower percentage of AMF colonisation than those with sand inoculated with R. irregularis. The differences in colonisation observed in experiments with R. irregularis are not observed in soils containing a diverse inoculum of AMF species. The transcriptomic data of the rice roots reveals that the expression of AM marker genes especially OsPT11 was significantly expressed in comparison with 2 mm mesh and control. This indicates that some of P were delivered to the rice plant through AMF symbiosis. Transcriptome analysis of contrasting genotypes and mesh treatments reveals a new understanding of AMF and P transporter and starvation genes, which provides important sources for the field of rice and AMF.22 0