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Title: OVER-EXPRESSION OF (AT) NPR1 IN RICE LEADS TO A BTH- AND ENVIRONMENT-INDUCIBLE LESION-MIMIC/CELL DEATH PHENOTYPE

Author
item FITZGERALD, HEATHER - UNIV OF CALIFORNIA-DAVIS
item CHERN, MAW-SHENG - UNIV OF CALIFORNIA-DAVIS
item Navarre, Duroy - Roy
item RONALD, PAMELA - UNIV OF CALIFORNIA-DAVIS

Submitted to: Molecular Plant Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2003
Publication Date: 2/10/2004
Citation: Fitzgerald, H.A., Chern, M., Navarre, D.A., Ronald, P.C. 2004. Over-expression of (At) NPR1 in rice leads to a bth- and environment-inducible lesion-mimic/cell death phenotype. Molecular Plant Microbe Interactions. 17(2):140-51.

Interpretive Summary: Systemic acquired resistance (SAR) is a mechanism by which plants protect themselves against a wide range of pathogens and is regulated by a compound called salicylic acid (SA). A key regulator of SAR in plants is a gene called NPR1. This gene has been used to give plants superior broad spectrum disease resistance. Rice making large amounts of NPR1 have enhanced resistance to a bacterial pathogen, but unlike some other plants also had additional effects that may affect its usefulness in some crops. Whether these effects are specific to plants with distinctive SA metabolism (rice and potato have much higher SA levels than most plants)remains to be determined.

Technical Abstract: Systemic acquired resistance (SAR) is an inducible defense response that protects plants against a broad-spectrum of pathogens. A central regulator of SAR in Arabidopsis is NPR1 (non-expresser of PR genes). In rice, over-expression of Arabidopsis NPR1 enhances plant resistance to the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo). This report demonstrates that over-expression of (At)NPR1 in rice also triggers a lesion-mimic/cell death (LMD) phenotype. The LMD phenotype is environmentally regulated and heritable. In addition, the development of lesions and death correlates with the expression of rice defense genes and the accumulation of hydrogen peroxide. Application of the salicylic acid (SA) analog, benzo (1,2,3) thiadiazole-7- carbothioc acid S-methyl ester(TH), potentiates this phenotype. Endogenous SA levels are reduced in rice over-expressing (At)NPR1 when compared with wild-type plants, supporting the idea that (At)NPR1 may perceive and modulate the accumulation of SA. The association of(At)NPR1 expression in rice with the development of a LMD phenotype suggests that (At)NPR1 has multiple roles in plant stress responses that may affect its efficacy as a transgenic tool for engineering broad-spectrum resistance.