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RCY1-Mediated Resistance to Cucumber mosaic virus Is Regulated by LRR Domain-Mediated Interaction with CMV(Y) Following Degradation of RCY1

September 2012 , Volume 25 , Number  9
Pages  1,171 - 1,185

Hideki Takahashi,1 Hiromi Shoji,1 Sugihiro Ando,1 Yoshinori Kanayama,1 Tomonobu Kusano,2 Minoru Takeshita,3 Masashi Suzuki,4 and Chikara Masuta5

1Department of Life Science, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan; 2Graduate School of Life Science, Tohoku University, Sendai 980-8577, Japan; 3Laboratory of Plant Pathology, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan; 4Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan; 5Graduate School of Agriculture, Hokkaido University, Kita-ku kita 9, Nishi 9, Sapporo 060-8589, Japan

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Accepted 25 May 2012.

RCY1, which encodes a coiled coil nucleotide-binding site leucine-rich repeat (LRR) class R protein, confers the hypersensitive response (HR) to a yellow strain of Cucumber mosaic virus (CMV[Y]) in Arabidopsis thaliana. Nicotiana benthamiana transformed with hemagglutinin (HA) epitope-tagged RCY1 (RCY1-HA) also exhibited a defense response accompanied by HR cell death and induction of defense-related gene expression in response to CMV(Y). Following transient expression of RCY1-HA by agroinfiltration, the defense reaction was induced in N. benthamiana leaves infected with CMV(Y) but not in virulent CMV(B2)-infected N. benthamiana leaves transiently expressing RCY1-HA or CMV(Y)-infected N. benthamiana leaves transiently expressing HA-tagged RPP8 (RPP8-HA), which is allelic to RCY1. This result suggests that Arabidopsis RCY1-conferred resistance to CMV(Y) could be reproduced in N. benthamiana leaves in a gene-for-gene manner. Expression of a series of chimeric constructs between RCY1-HA and RPP8-HA in CMV(Y)-infected N. benthamiana indicated that induction of defense responses to CMV(Y) is regulated by the LRR domain of RCY1. Interestingly, in CMV(Y)-infected N. benthamiana manifesting the defense response, the levels of both RCY1 and chimeric proteins harboring the RCY1 LRR domain were significantly reduced. Taken together, these data indicate that the RCY1-conferred resistance response to CMV(Y) is regulated by an LRR domain-mediated interaction with CMV(Y) and seems to be tightly associated with the degradation of RCY1 in response to CMV(Y).

© 2012 The American Phytopathological Society