Rgs1 regulates multiple Galpha subunits in Magnaporthe pathogenesis, asexual growth and thigmotropism.
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, magA(G187S) (RGS-insensitive Galpha(s)) and magA(Q208L) (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 Galpha(i) subunit MagB during asexual development. Deficiency of MAGB suppressed the hyper-conidiation defect in RGS1-deletion strain, whereas magB(G183S) and magB(Q204L) mutants produced more conidia, similar to the RGS1-deletion strain. Rgs1 physically interacted with GDP.AlF(4)(-)-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.
Liu
Hao
H
Fungal Patho-Biology Group, Temasek Life Sciences Laboratory, National University of Singapore, Singapore.
Suresh
Angayarkanni
A
Willard
Francis S
FS
Siderovski
David P
DP
Lu
Shen
S
Naqvi
Naweed I
NI
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits / Q000235:genetics / Q000378:metabolism*; D005816:Genetic Complementation Test; D006244:Hardness; D020082:Magnaporthe / Q000254:growth & development* / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D020710:RGS Proteins / Q000235:genetics / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D015398:Signal Transduction / Q000502:physiology*; D013172:Spores, Fungal / Q000254:growth & development / Q000378:metabolism*; D018523:Tropism / Q000502:physiology*
D044385:GTP-Binding Protein alpha Subunits; D020710:RGS Proteins; D000242:Cyclic AMP