Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/16231
Title: Analysis of regulator of G-protein signaling (RGS) function in growth, development and pathogenicity of Magnaporthe grisea
Authors: LIU HAO
Keywords: G-protein, RGS1, Magnaporthe grisea
Issue Date: 5-Jun-2007
Source: LIU HAO (2007-06-05). Analysis of regulator of G-protein signaling (RGS) function in growth, development and pathogenicity of Magnaporthe grisea. ScholarBank@NUS Repository.
Abstract: Heterotrimeric G proteins act as signal transducers that couple cell-surface receptors tocytoplasmic effector proteins. Regulators of G-protein signaling (RGS proteins) negatively regulate heterotrimeric G-protein cascades that enable eukaryotic cells to perceive and respond to external stimuli. In fungi, G proteins play essential roles during vegetative growth, sexual and pathogenic development. The rice-blast fungus Magnaporthe grisea forms specialized infection structures called appressoria in response to specific physical or chemical inductive cues. To identify elements involved in M. grisea pathogenicity-related development, Agrobacterium TDNA mediated random insertion was employed as a genetic tool to transform M. grisea to generate transgenic library. Magnaporthe RGS1 was isolated in this screen for mutants that form precocious appressoria on non-inductive surfaces. I report that a thigmotropic cue is necessary for initiating appressoria and for accumulating cAMP. Similar to an RGS1-deletion strain,magAG187S (RGS-insensitive Galpha(s)) mutants accumulated excessive cAMP and elaborated appressoria on non-inductive surfaces, suggesting that Rgs1 regulates MagA during appressorium formation. Rgs1 was also found to negatively regulate the Galpha(i) subunit MagB during asexual development. Deficiency of MAGB suppressed the hyper-conidiation defect in RGS1-deletion strain, whereas magBG183S mutants produced more conidia, similar to the RGS1-deletion strain. Rgs1 physically interacted with GDP-AlF4--activated forms of MagA, MagB and MagC (a Galpha(II) subunit). Thus, Rgs1 serves as a negative regulator of all Galpha subunits in Magnaporthe and controls important developmental events during asexual and pathogenic development.
URI: http://scholarbank.nus.edu.sg/handle/10635/16231
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