Enhanced disease resistance and hypersensitivity to BTH by introduction of an NH1/OsNPR1 paralog.
Non-expresser of pathogenesis-related genes 1 (NPR1) is the master regulator of salicylic acid-mediated systemic acquired resistance. Over-expression of Arabidopsis NPR1 and rice NH1 (NPR1 homolog1)/OsNPR1 in rice results in enhanced resistance. While there are four rice NPR1 paralogs in the rice genome, none have been demonstrated to function in disease resistance. To study rice NPR1 paralog 3, we introduced constructs into rice and tested for effects on resistance to infection by Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial blight. While over-expression of NH3 using the maize ubiquitin-1 promoter failed to enhance resistance, introduction of an extra copy of NH3 driven by its own promoter (nNT-NH3) resulted in clear, enhanced resistance. Progeny analysis confirms that the enhanced resistance phenotype, measured by Xoo-induced lesion length, is associated with the NH3 transgene. Bacterial growth curve analysis indicates that bacterial population levels are reduced 10-fold in nNT-NH3 lines compared to control rice lines. The transgenic plants exhibit higher sensitivity to benzothiadiazole (BTH) and 2,6-dichloroisonicotinic acid (INA) treatment as measured by increased cell death. Expression analysis of pathogenesis-related (PR) genes showed that nNT-NH3 plants display greatly enhanced induction of PR genes only after treatment with BTH. Our study demonstrates an alternative method to employ a regulatory protein to enhance plant defence. This approach avoids using undesirable constitutive, high-level expression and may prove to be more practical for engineering resistance.
Bai
Wei
W
Department of Plant Pathology, University of California, Davis, CA, USA.
Chern
Mawsheng
M
Ruan
Deling
D
Canlas
Patrick E
PE
Sze-To
Wing Hoi
WH
Ronald
Pamela C
PC
D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D007113:Immunity, Innate / Q000235:genetics; D012275:Oryza / Q000235:genetics* / Q000276:immunology / Q000382:microbiology; D010641:Phenotype; D010935:Plant Diseases / Q000235:genetics*; D010940:Plant Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000276:immunology / Q000378:metabolism; D011401:Promoter Regions, Genetic; D013830:Thiadiazoles / Q000494:pharmacology*; D025822:Ubiquitin C / Q000235:genetics; D014974:Xanthomonas
D029681:Arabidopsis Proteins; C105496:NPR1 protein, Arabidopsis; D010940:Plant Proteins; D013830:Thiadiazoles; C417884:Ubi-1 protein, Zea mays; D025822:Ubiquitin C; C015700:benzo-1,2,3-thiadiazole