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The Heterotrimeric G Protein α Subunit Acts Upstream of the Small GTPase Rac in Disease Resistance of Rice

Utut Suharsono, Yukiko Fujisawa, Tsutomu Kawasaki, Yukimoto Iwasaki, Hikaru Satoh and Ko Shimamoto
Proceedings of the National Academy of Sciences of the United States of America
Vol. 99, No. 20 (Oct. 1, 2002), pp. 13307-13312
Stable URL: http://www.jstor.org/stable/3073392
Page Count: 6
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
The Heterotrimeric G Protein α Subunit Acts Upstream of the Small GTPase Rac in Disease Resistance of Rice
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Abstract

We used rice dwarf1 (d1) mutants lacking a single-copy Gα gene and addressed Gα's role in disease resistance. d1 mutants exhibited a highly reduced hypersensitive response to infection by an avirulent race of rice blast. Activation of PR gene expression in the leaves of the mutants infected with rice blast was delayed for 24 h relative to the wild type. H2O 2 production and PR gene expression induced by sphingolipid elicitors (SE) were strongly suppressed in d1 cell cultures. Expression of the constitutively active OsRac1, a small GTPase Rac of rice, in d1 mutants restored SE-dependent defense signaling and resistance to rice blast. Gα mRNA was induced by an avirulent race of rice blast and SE application on the leaf. These results indicated the role of Gα in R gene-mediated disease resistance of rice. We have proposed a model for the defense signaling of rice in which the heterotrimeric G protein functions upstream of the small GTPase OsRac1 in the early steps of signaling.

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