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  • The EMBO Journal (2007) 26, 690 - 700
  • doi:10.1038/sj.emboj.7601536

Published online: 25 January 2007

Rgs1 regulates multiple Galpha subunits in Magnaporthe pathogenesis, asexual growth and thigmotropism

Hao Liu1, Angayarkanni Suresh1, Francis S Willard2, David P Siderovski2, Shen Lu3 and Naweed I Naqvi1,4

  1. Fungal Patho-Biology Group, Temasek Life Sciences Laboratory, National University of Singapore, Singapore
  2. Department of Pharmacology, University of North Carolina, Chapel Hill, NC, USA
  3. Institute of Materials Research and Engineering, Singapore
  4. Department of Biological Sciences, National University of Singapore, Singapore

Correspondence to:

Naweed I Naqvi, Fungal Patho-Biology Group, Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore. Tel.: +65 6872 7493; Fax: +65 6872 7007; E-mail: naweed@tll.org.sg

Received 27 June 2006; Accepted 11 December 2006

Regulators of G-protein signaling (RGS proteins) negatively regulate heterotrimeric G-protein cascades that enable eukaryotic cells to perceive and respond to external stimuli. The rice-blast fungus Magnaporthe grisea forms specialized infection structures called appressoria in response to inductive surface cues. We isolated Magnaporthe RGS1 in a screen for mutants that form precocious appressoria on non-inductive surfaces. We report that a thigmotropic cue is necessary for initiating appressoria and for accumulating cAMP. Similar to an RGS1-deletion strain, magAG187S (RGS-insensitive Galphas) and magAQ208L (GTPase-dead) mutants accumulated excessive cAMP and elaborated appressoria on non-inductive surfaces, suggesting that Rgs1 regulates MagA during pathogenesis. Rgs1 was also found to negatively regulate the Galphai subunit MagB during asexual development. Deficiency of MAGB suppressed the hyper-conidiation defect in RGS1-deletion strain, whereas magBG183S and magBQ204L mutants produced more conidia, similar to the RGS1-deletion strain. Rgs1 physically interacted with GDPdotAlF4--activated forms of MagA, MagB and MagC (a GalphaII subunit). Thus, Rgs1 serves as a negative regulator of all Galpha subunits in Magnaporthe and controls important developmental events during asexual and pathogenic development.

  • Keywords:

    • fungal pathogenesis,
    • G-proteins,
    • Magnaporthe,
    • RGS proteins,
    • thigmotropism