Shang, Yue (2003-05). Analysis of secreted proteins of Magnaporthe grisea and the search for protein effectors. Master's Thesis. Thesis uri icon

abstract

  • Magnaporthe grisea is a notorious pathogenic fungus that causes rice blast disease worldwide. Proteins secreted by the fungus are likely candidates for being effectors that are potentially recognized by determinants of resistance or susceptibility in host plants. However, knowledge of the role of secreted proteins of M. grisea is still limited. In this study, I identified 29 proteins that were secreted into culture filtrates from M. grisea strains expressing candidate proteins. I confirmed secretion of these proteins and tested them for elicitor activity on plants. Among them, I studied two groups: cell wall degrading enzymes (CWDEs) and small cysteine-rich proteins. Cysteine-rich proteins have been shown in other systems to function as elicitors. Initially, I expressed and purified proteins in M. grisea to obtain proteins by a homologous expression system. Although this was effective for a number of proteins, the need for greater amounts of protein led me to express several proteins in the Pichia pastoris system. Several candidate proteins were purified and found to induce symptoms on rice and maize. Hypothetical proteins MG10424.4 and MG09998.4 were both found to have elicitor activity. Lipase MG07016.4 did not induce response of plants and we concluded that the lipase activity of MG07016.4 does not function as an elicitor. I also purified a small cysteine-rich protein, which belongs to the group of cluster 180 proteins in M. grisea, MG10732.4 from P. pastoris. It is able to cause yellowing symptoms and hydrogen peroxide production in plants and it might contain elicitor activity.
  • Magnaporthe grisea is a notorious pathogenic fungus that causes rice blast disease
    worldwide. Proteins secreted by the fungus are likely candidates for being effectors that
    are potentially recognized by determinants of resistance or susceptibility in host plants.
    However, knowledge of the role of secreted proteins of M. grisea is still limited. In this
    study, I identified 29 proteins that were secreted into culture filtrates from M. grisea
    strains expressing candidate proteins. I confirmed secretion of these proteins and tested
    them for elicitor activity on plants. Among them, I studied two groups: cell wall
    degrading enzymes (CWDEs) and small cysteine-rich proteins. Cysteine-rich proteins
    have been shown in other systems to function as elicitors. Initially, I expressed and
    purified proteins in M. grisea to obtain proteins by a homologous expression system.
    Although this was effective for a number of proteins, the need for greater amounts of
    protein led me to express several proteins in the Pichia pastoris system. Several candidate
    proteins were purified and found to induce symptoms on rice and maize. Hypothetical
    proteins MG10424.4 and MG09998.4 were both found to have elicitor activity. Lipase
    MG07016.4 did not induce response of plants and we concluded that the lipase activity of
    MG07016.4 does not function as an elicitor. I also purified a small cysteine-rich protein,
    which belongs to the group of cluster 180 proteins in M. grisea, MG10732.4 from P. pastoris. It is able to cause yellowing symptoms and hydrogen peroxide production in
    plants and it might contain elicitor activity.

publication date

  • May 2003