Molecular Genetic Analysis of NRR, a Negative Regulator of Disease Resistance

系统获得性抗性（SAR）是在坏死病原体局部感染后诱导的，并使植物的未感染部分对多种通常有毒的病毒、细菌和真菌具有抗性。SAR与病程相关（PR）基因的诱导表达有关。在双子叶植物中，植物激素水杨酸（SA）是诱导SAR的必要和充分的。NPR 1蛋白是拟南芥中SA介导的SAR的关键调节因子。npr 1突变体不能表达SAR相关的PR基因，并且即使在SA处理后也显示出对病原体感染的增强的易感性。此外，NPR 1在拟南芥中的过表达以剂量依赖性方式增强了对细菌和真菌病原体的抗病性。我们现在已经表明，NPR 1在水稻中的过表达导致对细菌病原体黄单胞菌致病型的抗性增强。稻曲病（Xoo）是一种世界性的水稻病害。 此外，我们还从水稻中分离出了三个抗性信号组分：一个水稻NPR 1同源物，NH 1，以及两个编码与NH 1和NPR 1相互作用的产物的基因; bZIP转录因子rTGA2.1和一种以前未鉴定的信号传导组分，NRR（抗病负调节）。长-该提案的长期目标是进一步阐明控制植物抗病性的信号级联，并为水稻和其他谷类作物的疾病控制创造新的策略。

Systemic acquired resistance (SAR) is induced after a local infection by necrotizing pathogens and renders uninfected parts of the plant resistant to a variety of normally virulent viruses, bacterial and fungi. SAR is associated with the inducible expression of pathogenesis-related (PR) genes. In dicots, the phytohormone salicylic acid (SA) is both necessary and sufficient for the induction of SAR. The NPR1 protein is a key regulator of SA-mediated SAR in Arabidopsis. npr1 mutants fail to express SAR related PR genes and display enhanced susceptibility to pathogen infection even after treatment with SA. Furthermore, over-expression of NPR1 in Arabidopsis leads to enhanced disease resistance to both bacterial and fungal pathogens in a dose-dependent manner. We have now shown that over-expression of NPR1 in rice leads to enhanced resistance to the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo), a serious disease of rice throughout the world. In addition, we have isolated three resistance signaling components from rice: a rice NPR1 homolog, NH1, and two genes that encode products that interact with NH1 and NPR1; a bZIP transcription factor, rTGA2.1, and a previously unidentified signaling component, NRR (Negative Regulator of disease Resistance).The long-term goal of this proposal is to further elucidate the signal cascade governing plant disease resistance and to create novel strategies for disease control in rice and other cereal crops.