Plant Cell
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
QUICK SEARCH:   [advanced]


     

Plant Cell Advance Online Publication
Published on December 21, 2007; 10.1105/tpc.107.055517

OPEN ACCESS ARTICLE
This Article
Free via Open Access: OA
Right arrow Full Text - TPC Advance Online Pub. (PDF)
Right arrow Supplemental Data
Right arrowOA All Versions of this Article:
19/12/4035    most recent
tpc.107.055517v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Thao, N. P.
Right arrow Articles by Shimamoto, K.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Thao, N. P.
Right arrow Articles by Shimamoto, K.
Agricola
Right arrow Articles by Thao, N. P.
Right arrow Articles by Shimamoto, K.

Received September 5, 2007
Returned for revision November 22, 2007
Accepted December 7, 2007

RAR1 and HSP90 Form a Complex with Rac/Rop GTPase and Function in Innate-Immune Responses in Rice

Nguyen Phuong Thao 1, Letian Chen 1, Ayako Nakashima 1, Shin-ichiro Hara 1, Kenji Umemura 2, Akira Takahashi 3, Ken Shirasu 3, Tsutomu Kawasaki 1, and Ko Shimamoto 3*

1 Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, Ikoma 630-0101, Japan
2 Agricultural and Veterinary Research Lab, Meiji Seika Kaisha, Kohoku-ku, Yokohama 222-8567 Japan
3 Sainsbury Laboratory, John Innes Centre, Norwich NR4 7UH, United Kingdom

* To whom correspondence should be addressed. E-mail: simamoto{at}bs.naist.jp.

A rice (Oryza sativa) Rac/Rop GTPase, Os Rac1, is involved in innate immunity, but its molecular function is largely unknown. RAR1 (for required for Mla12 resistance) and HSP90 (a heat shock protein 90 kD) are important components of R gene–mediated disease resistance, and their function is conserved in several plant species. HSP90 has also recently been shown to be important in mammalian innate immunity. However, their functions at the molecular level are not well understood. In this study, we examined the functional relationships between Os Rac1, RAR1, and HSP90. Os RAR1-RNA interference (RNAi) rice plants had impaired basal resistance to a compatible race of the blast fungus Magnaporthe grisea and the virulent bacterial blight pathogen Xanthomonas oryzae. Constitutively active Os Rac1 complemented the loss of resistance, suggesting that Os Rac1 and RAR1 are functionally linked. Coimmunoprecipitation experiments with rice cell culture extracts indicate that Rac1 forms a complex with RAR1, HSP90, and HSP70 in vivo. Studies with Os RAR1-RNAi and treatment with geldanamycin, an HSP90-specific inhibitor, showed that RAR1 and HSP90 are essential for the Rac1-mediated enhancement of pathogen-associated molecular pattern–triggered immune responses in rice cell cultures. Furthermore, the function of HSP90, but not RAR1, may be essential for their association with the Rac1 complex. Os Rac1 also regulates RAR1 expression at both the mRNA and protein levels. Together, our results indicate that Rac1, RAR1, HSP90, and HSP70 form one or more protein complexes in rice cells and suggest that these proteins play important roles in innate immunity in rice.






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
ASPB Publications THE PLANT CELL PLANT PHYSIOLOGY
Copyright © 2007 by the American Society of Plant Biologists