Browsing by Author "Onyilo, Francis"

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    Agrobacterium tumefaciens-Mediated Transformation of Pseudocercospora fijiensis to Determine the Role of PfHog1 in Osmotic Stress Regulation and Virulence Modulation
    (Frontiers in Microbiology, 2017) Onyilo, Francis; Tusiime, Geoffrey; Chen, Li-Hung; Falk, Bryce; Stergiopoulos, Ioannis; Tripathi, Jaindra N.; Tushemereirwe, Wilberforce; Kubiriba, Jerome; Changa, Charles; Tripathi, Leena
    Black Sigatoka disease, caused by Pseudocercospora fijiensis is a serious constraint to banana production worldwide. The disease continues to spread in new ecological niches and there is an urgent need to develop strategies for its control. The high osmolarity glycerol (HOG) pathway in Saccharomyces cerevisiae is well known to respond to changes in external osmolarity. HOG pathway activation leads to phosphorylation, activation and nuclear transduction of the HOG1 mitogen-activated protein kinases (MAPKs). The activated HOG1 triggers several responses to osmotic stress, including up or down regulation of different genes, regulation of protein translation, adjustments to cell cycle progression and synthesis of osmolyte glycerol. This study investigated the role of the MAPK-encoding PfHog1 gene on osmotic stress adaptation and virulence of P. fijiensis. RNA interference-mediated gene silencing of PfHog1 significantly suppressed growth of P. fijiensis on potato dextrose agar media supplemented with 1 M NaCl, indicating that PfHog1 regulates osmotic stress. In addition, virulence of the PfHog1-silenced mutants of P. fijiensis on banana was significantly reduced, as observed from the low rates of necrosis and disease development on the infected leaves. Staining with lacto phenol cotton blue further confirmed the impaired mycelial growth of the PfHog1 in the infected leaf tissues, which was further confirmed with quantification of the fungal biomass using absolutequantitative PCR. Collectively, these findings demonstrate that PfHog1 plays a critical role in osmotic stress regulation and virulence of P. fijiensis on its host banana. Thus, PfHog1 could be an interesting target for the control of black Sigatoka disease in banana.
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    Challenges and innovations in achieving zero hunger and environmental sustainability through the lens of sub-Saharan Africa
    (Outlook on Agriculture, 2020) Okello, Moses; Lamo, Jimmy; Ochwo-Ssemakula, Mildred; Onyilo, Francis
    Achieving zero hunger by 2030 often raises the issue of environmental protection or sustainable social development among policy makers due to the environmental footprint of intensifying agricultural production across the continent. Sub- Saharan Africa (SSA) has one of the fastgrowing populations with more than half of the global growth between now and 2050. The challenge now lies in feeding the ever-growing population that is exerting pressure on the limited available resources. Doubling the agricultural productivity of small-scale farmers by 2030 (SDG 2.3) remains a daunting task for researcher and policy makers to address on the continent that now relies much on imports of food. Exploitation of the untapped massive land resources for agricultural production poses threats to sustainability. However, the challenges of global warming cannot be left out of this discussion since it has direct impact on future productivity on the continent. Climate change that has been projected to mostly affect the poorer countries also present trials to the food system through increased diseases and weather extremes of floods and droughts. Questions are yet to be answered on which tradeoffs and synergies if any need to be made to achieve zero hunger in Africa by 2030. This synopsis critically breaks down the conflicts, tradeoffs and synergies of how a continent with such massive agricultural production potential can navigate sustainably to achieve zero hunger, self-sufficiency and exports prospects while conserving the environment and natural resources. Evident deployment of new and improved technologies especially advanced biotechnology tools will be critical in achieving zero hunger by 2030. The adaptation needs of the continent are broad including institutional, social, physical and infrastructural needs, ecosystem services and environmental needs, and financial and capacity uncertain impacts.
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    Silencing of the Mitogen-Activated Protein Kinases (MAPK) Fus3 and Slt2 in Pseudocercospora fijiensis Reduces Growth and Virulence on Host Plants
    (Frontiers in Plant Science, 2018) Onyilo, Francis; Tusiime, Geoffrey; Tripathi, Jaindra N.; Chen, Li-Hung; Falk, Bryce; Stergiopoulos, Ioannis; Tushemereirwe, Wilberforce; Kubiriba, Jerome; Tripathi, Leena
    Pseudocercospora fijiensis, causal agent of the black Sigatoka disease (BSD) of Musa spp., has spread globally since its discovery in Fiji 1963 to all the banana and plantain growing areas across the globe. It is becoming the most damaging and economically important disease of this crop. The identification and characterization of genes that regulate infection processes and pathogenicity in P. fijiensis will provide important knowledge for the development of disease-resistant cultivars. In many fungal plant pathogens, the Fus3 and Slt2 are reported to be essential for pathogenicity. Fus3 regulates filamentous-invasion pathways including the formation of infection structures, sporulation, virulence, and invasive and filamentous growth, whereas Slt2 is involved in the cell-wall integrity pathway, virulence, invasive growth, and colonization in host tissues. Here, we used RNAi-mediated gene silencing to investigate the role of the Slt2 and Fus3 homologs in P. fijiensis in pathogen invasiveness, growth and pathogenicity. The PfSlt2 and PfFus3 silenced P. fijiensis transformants showed significantly lower gene expression and reduced virulence, invasive growth, and lower biomass in infected leaf tissues of East African Highland Banana (EAHB). This study suggests that Slt2 and Fus3 MAPK signaling pathways play important roles in plant infection and pathogenic growth of fungal pathogens. The silencing of these vital fungal genes through host-induced gene silencing (HIG) could be an alternative strategy for developing transgenic banana and plantain resistant to BSD.