Download or read book Investigating Virus-mediated Disruption of the Polyamine Metabolism Pathway in the Plant Pathogen Cryphonectria Parasitica written by Mona Pokharel and published by . This book was released on 2016 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the plant pathogenic fungus Cryphonectria parasitica, infection with hypovirus has been shown to alter various metabolic pathways. One such pathway is the synthesis of the polyamines, putrescine and spermidine, which are required for growth and development of the fungus. While the function of polyamines in various cellular processes has been extensively studied in other fungi, less is known about the effects of viral infection on polyamine metabolism. This study demonstrated the significantly higher accumulation of spermidine in virus-infected mycelium in comparison to uninfected tissue by thin layer chromatography. To understand the possible molecular mechanism for this differential accumulation, we investigated different catalytic enzymes and regulatory components involved in the biosynthesis of polyamines. The enzyme that catalyzes an initial (rate-limiting) step for polyamine biosynthesis is ornithine decarboxylase (ODC). Western blot analyses of ODC showed higher abundance in virus free than compared to the virus-infected strain. ODC is subject to a complex post-translational regulatory pathway through inhibition by an antizyme AZ. When examined by western blot, we observed the abundance of AZ at a level that corresponded to the level of ODC and, therefore, we hypothesized that the cause of the elevated spermidine levels in the absence of the virus would instead be through an alternate part of the pathway. Given that this pathway is a single route-synthesis, where formation of different polyamines occurs only via ornithine, we then examined the levels of S-Adenosylmethionine decarboxylase (SAMDC) that supplies a key component, the aminopropyl moiety, in the conversion of putrescine to form spermidine. In this case, we observed a higher SAMDC accumulation in the virus infected than the virus free strain, thus permitting increased synthesis of spermidine even though the accumulation of ODC is paradoxically lower. Therefore, this study provides a mechanistic model to explain the observed differences in polyamine accumulation following virus infection.