Table_4_Lack of a Cytoplasmic RLK, Required for ROS Homeostasis, Induces Strong Resistance to Bacterial Leaf Blight in Rice.DOCX

Many scientific findings have been reported on the beneficial function of reactive oxygen species (ROS) in various cellular processes, showing that they are not just toxic byproducts. The double-edged role of ROS shows the importance of the regulation of ROS level. We report a gene, rrsRLK (required for ROS-scavenging receptor-like kinase), that encodes a cytoplasmic RLK belonging to the non-RD kinase family. The gene was identified by screening rice RLK mutant lines infected with Xanthomonas oryzae pv. oryzae (Xoo), an agent of bacterial leaf blight of rice. The mutant (ΔrrsRLK) lacking the Os01g02290 gene was strongly resistant to many Xoo strains, but not to the fungal pathogen Magnaporthe grisea. ΔrrsRLK showed significantly higher expression of OsPR1a, OsPR1b, OsLOX, RBBTI4, and jasmonic acid-related genes than wild type. We showed that rrsRLK protein interacts with OsVOZ1 (vascular one zinc-finger 1) and OsPEX11 (peroxisomal biogenesis factor 11). In the further experiments, abnormal biogenesis of peroxisomes, hydrogen peroxide (H2O2) accumulation, and reduction of activity of ROS-scavenging enzymes were investigated in ΔrrsRLK. These results suggest that the enhanced resistance in ΔrrsRLK is due to H2O2 accumulation caused by irregular ROS-scavenging mechanism, and rrsRLK is most likely a key regulator required for ROS homeostasis in rice.

众多科学研究揭示了活性氧物种（ROS）在多种细胞过程中的有益功能，表明其并非仅仅是毒性副产物。ROS的双重作用凸显了调节ROS水平的重要性。本研究报道了一个基因rrsRLK（ROS清除受体样激酶所需基因），该基因编码一种属于非RD激酶家族的细胞质RLK。该基因通过筛选感染稻瘟病菌（Xanthomonas oryzae pv. oryzae，Xoo，水稻细菌性叶斑病的病原体）的稻突变体线而得以鉴定。缺乏Os01g02290基因的突变体（ΔrrsRLK）对多种Xoo菌株具有强烈的抗性，但对真菌病原体Magnaporthe grisea则无抗性。ΔrrsRLK相较于野生型表现出显著更高的OsPR1a、OsPR1b、OsLOX、RBBTI4和茉莉酸相关基因的表达。研究表明，rrsRLK蛋白与OsVOZ1（血管性锌指蛋白1）和OsPEX11（过氧化物酶体生物发生因子11）相互作用。在后续实验中，对ΔrrsRLK中的过氧化物酶体异常生物发生、过氧化氢（H2O2）积累以及ROS清除酶活性的降低进行了研究。这些结果表明，ΔrrsRLK增强的抗性是由于不规则ROS清除机制导致的H2O2积累，而rrsRLK很可能是维持水稻ROS稳态的关键调节因子。