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

系统性获得性抗性（SAR）是在坏死性病原体局部感染后诱导的，并使植物未感染的部分对各种通常有毒的病毒、细菌和真菌产生抗性。SAR与致病相关（PR）基因的诱导表达有关。在拟南芥中，植物激素水杨酸（SA）对SAR的诱导既必要又充分。NPR1蛋白是SA介导的SAR的关键调节因子。npr1突变体不能表达SAR相关的PR基因，即使在SA治疗后也表现出对病原体感染的易感性。此外，NPR1在拟南芥中的过度表达以剂量依赖的方式增强了对细菌和真菌病原体的抗病能力。我们现在已经证明，水稻中NPR1的过度表达导致对细菌病原体米黄单胞菌pv的抗性增强。稻瘟病（Xoo）是一种世界性的严重水稻病害。此外，我们从水稻中分离出三种抗性信号成分：水稻NPR1同源物NH1和两个编码与NH1和NPR1相互作用产物的基因；一个bZIP转录因子，rTGA2.1，和一个以前未知的信号成分，NRR（抗病负调节因子）。本研究的长期目标是进一步阐明控制植物抗病的信号级联，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.