PHD-Department of Biochemistry and Biotechnology

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Browsing PHD-Department of Biochemistry and Biotechnology by Author "Gilles, Irafasha"

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    Genetic Mechanisms of Pre-Attachment Striga hermonthica (Del.) Benth., Resistance in Sorghum Revealed by Ribonucleic Acid Sequencing
    (Kenyatta University, 2024-03) Gilles, Irafasha
    Striga hermonthica is an obligate root parasitic plant that has a significant negative impact on the yield of major crops in sub-Saharan Africa, causing devastating yield loss to already struggling economies. This parasite has purple flowers with tinny dusty seeds of 0.2 to 0.5 mm that are easily dispersed. Within the soil, they can stay dormant for up to a decade waiting for ideal conditions to align, to ensure successful germination near a potential host. S. hermonthica seeds germination is a decision mediated by endogenous hormones in response to different environmental cues, of which the most important are different strigolactones which are found within a complex blend of many secondary metabolites exuding from nearby plant roots. Although S. hermonthica seeds depend on strigolactones to germinate, little is known about how it produces or uses hormones that play important roles in the germination of its seeds and how they react to differences in root exudate composites from potential hosts as they germinate. This study presents a transcriptomics analysis of how hormones regulate S. hermonthica seeds germination upon exposure to root exudates from both susceptible and resistant sorghum genotypes, and a synthetic Strigolactone GR24. The study investigated the expression patterns of genes involved in the biosynthesis of major hormones during S. hermonthica seed germination at different time points (6, 12, and 18 hours) upon germination induction and used preconditioned but untreated seeds as control. Resulted transcripts entail that Violaxanthin de-epoxidase (VDE) inhibits the ABA biosynthesis a hormone that promotes seeds dormancy. The biosynthesis of Gibberellic acid (GA1 and GA4) promotes seed germination and its biosynthesis was highly enriched at 18 hours in seeds treated with SRN39 root exudates, suggesting that the pre-attachment resistance associated with this genotype is due to delayed germination in contrast to other resistant genotypes (IS27146 and IS 41724), ABA and Auxin were highly upregulated in seed that showed the least germination metrics. Overall, GA and ABA were the main hormones that controlled germination and GR24-treated seeds showed a relatively different germination mechanism from what was observed in seeds treated with sorghum root exudates. This study shows how S. hermonthica germination program and rate varies according to different germination stimulants from root exudates. Therefore, profiling of these root exudates is recommended. Findings in this study are necessary for future Striga resistant sorghum breeding programs.